Anorexia Nervosa

Psychiatric MONDO:0005351 Pathograph 29 Show in embeddings browser Eating Disorder Mental Health Disorder

Anorexia nervosa is a serious eating disorder defined by persistent energy restriction leading to significantly low body weight, together with intense fear of weight gain or persistent behavior that interferes with weight gain and disturbance in body-weight or shape experience. This parent entry covers both restricting and binge-eating/purging presentations. It distinguishes the established physiological consequences of undernutrition from proposed upstream neural, metabolic, immune, and microbiome mechanisms.

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1
Inheritance
13
Pathophys.
13
Phenotypes
4
Hypotheses
29
Pathograph
1
Genes
6
Medical Actions
2
Subtypes
2
Differentials
3
Datasets
1
Trials
2
Deep Research
👪

Inheritance

1
Polygenic inheritance HP:0010982
AN has substantial heritability and a common-variant architecture; it is not modeled as a Mendelian disorder.
Polygenic inheritance
Show evidence (1 reference)
PMID:31308545 SUPPORT Human Clinical
"Characterized primarily by a low body-mass index, anorexia nervosa is a complex and serious illness1, affecting 0.9-4% of women and 0.3% of men2-4, with twin-based heritability estimates of 50-60%5."
The GWAS report summarizes twin heritability and then identifies multiple common-variant loci, supporting polygenic rather than Mendelian inheritance.
◆

Subtypes

2
Restricting presentation
Presentation without recurrent binge eating or purging during the relevant diagnostic interval.
Show evidence (1 reference)
PMID:16962383 SUPPORT Human Clinical
"Studies focusing on general outcome and medical comorbidity describe a worse outcome in the binge eating/purging subtype of anorexia nervosa compared to the restricting subtype."
The review explicitly distinguishes the restricting presentation from the binge-eating/purging presentation.
Binge-eating/purging presentation
Presentation with recurrent binge eating or purging during the relevant diagnostic interval; purging-related electrolyte complications require separate clinical attention.
Show evidence (1 reference)
PMID:16962383 SUPPORT Human Clinical
"Studies focusing on general outcome and medical comorbidity describe a worse outcome in the binge eating/purging subtype of anorexia nervosa compared to the restricting subtype."
The review explicitly distinguishes the binge-eating/purging presentation from the restricting presentation.
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Mechanistic Hypotheses

4
Hypoleptinemia-driven starvation-induced hyperactivity
leptin_hyperactivity EMERGING
Evidence balance 1 support
The hypothesis that low circulating leptin is a causal driver of the physical hyperactivity and motor restlessness of AN, not merely a correlate. The causal step is demonstrated in the rodent activity-based anorexia (ABA) model, where recombinant leptin suppresses semi-starvation-induced hyperactivity; human evidence is correlational (an inverted U-shaped leptin-activity relationship) and inconsistent, so the causal claim is retained as emerging pending controlled human testing.
Pathograph links
Hypoleptinemia -> Excessive Physical Activity INDIRECT KNOWN INTERMEDIATES Low leptin is hypothesized to drive starvation-induced hyperactivity; the causal step is established in the ABA rodent model (via VTA STAT3 signaling) but only correlational (inverted-U) in humans, so this edge is carried under an emerging hypothesis rather than as an established human mechanism. Intermediates: Leptin signal transduction via STAT3 in ventral tegmental area (VTA) dopaminergic neurons (demonstrated in the activity-based anorexia model)
Show evidence (1 reference)
PMID:31156489 SUPPORT Model Organism
"the rat model activity-based anorexia (ABA) convincingly demonstrates the pivotal role of hypoleptinemia in the development of starvation-induced hyperactivity."
The ABA rodent model provides the primary causal evidence linking hypoleptinemia to starvation-induced hyperactivity; human confirmation is still lacking, which is why this group is EMERGING.
Polygenic metabo-psychiatric liability
metabo_psychiatric_liability CANONICAL
Evidence balance 1 support
Common-variant liability spans psychiatric, physical-activity, metabolic, lipid, and anthropometric traits. This is a robust genetic architecture, but the intermediate molecular and circuit mechanisms leading to restrictive eating remain unresolved.
Pathograph links
Polygenic Metabo-Psychiatric Susceptibility -> Restrictive-Eating Psychopathology INDIRECT UNKNOWN INTERMEDIATES Polygenic liability is placed upstream of the diagnostic psychopathology, but the intervening developmental, molecular, and neural mechanisms are unresolved.
Show evidence (1 reference)
PMID:31308545 SUPPORT Human Clinical
"The genetic architecture of anorexia nervosa mirrors its clinical presentation, showing significant genetic correlations with psychiatric disorders, physical activity, and metabolic (including glycemic), lipid and anthropometric traits, independent of the effects of common variants associated..."
GWAS genetic correlations support a metabo-psychiatric susceptibility model while not identifying a direct causal mediator.
Neural state-and-trait model
neural_state_trait_model EMERGING
Evidence balance 2 support
Structural and functional brain alterations may include both trait-like vulnerabilities and consequences of acute undernutrition. Imaging association alone cannot determine which changes initiate restrictive eating, so this model is kept separate from the established starvation cascade.
Pathograph links
Low Weight and Malnutrition -> Undernutrition-Associated Brain Structural Changes INDIRECT KNOWN INTERMEDIATES A substantial component of widespread brain structural differences is associated with acute undernutrition and is smaller after partial weight restoration. Intermediates: Acute undernutrition and lower body mass index
Show evidence (2 references)
PMID:34296492 SUPPORT Human Clinical
"This multimodal meta-analysis identified reductions of gray matter and functional activity in the anterior and median cingulate in patients with AN, which contributes to further understanding of the pathophysiology of AN."
Multimodal case-control imaging supports reproducible neural correlates.
PMID:36031441 SUPPORT Human Clinical
"Highlighting the effects of undernutrition, these deficits were associated with lower body mass index in the AN sample and were less pronounced in partially weight-restored patients."
Weight-state dependence limits causal interpretation of brain structural differences as primary disease drivers.
Immune and microbiome correlates
immune_microbiome_correlates EMERGING
Evidence balance 1 support
Cytokine and microbiome differences have been observed during acute illness and recovery, but current human studies are associative and do not establish whether these changes initiate, maintain, or merely reflect starvation.
Show evidence (1 reference)
DOI:10.3390/nu16111596 SUPPORT Human Clinical
"We found associations between cytokines and bodyweight, illness duration, depressive symptoms, and the microbiome."
Longitudinal adolescent data support correlated immune and microbiome changes, not a demonstrated causal direction.
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Pathophysiology

13
Polygenic Metabo-Psychiatric Susceptibility
Common germline variation contributes distributed susceptibility across psychiatric and metabolic trait domains. The node does not assert a single causal gene or a known molecular route to AN.
Polygenic metabo-psychiatric liability
Downstream
Restrictive-Eating Psychopathology Polygenic liability is placed upstream of the diagnostic psychopathology, but the intervening developmental, molecular, and neural mechanisms are unresolved. Polygenic metabo-psychiatric liability
Show evidence (1 reference)
PMID:31308545 SUPPORT Human Clinical
"These results further encourage a reconceptualization of anorexia nervosa as a metabo-psychiatric disorder."
The landmark GWAS supports the metabo-psychiatric susceptibility framing.
Restrictive-Eating Psychopathology
Fear of weight gain, disturbance in body-weight or shape experience, and persistent weight-gain-interfering behavior motivate restriction. This clinical state is established; its upstream molecular and circuit causes remain incompletely resolved.
regulation of appetite GO:0032098 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal regulation of appetite (GO:0032098). GO:0032098 is a biological process from the Gene Ontology. ⚠ ABNORMAL feeding behavior GO:0007631 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal feeding behavior (GO:0007631). GO:0007631 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Abnormal Eating Behavior Fear of weight gain, body-image disturbance, and persistent weight-gain-interfering behavior are expressed clinically as restrictive eating and related abnormal eating behavior.
Sustained Energy Restriction AN psychopathology motivates severe dietary restriction and other weight-loss behavior.
Show evidence (1 reference)
clinicaltrials:NCT03984344 SUPPORT Human Clinical
"Anorexia Nervosa (AN) is a life-threatening eating disorder characterised by an intense fear of weight gain and disturbed body image, which motivates severe dietary restriction or other weight loss behaviours (e.g. purging)."
The clinical-trial background summarizes the core psychopathology and restrictive behavior.
Sustained Energy Restriction
Persistent caloric restriction creates negative energy balance; in the binge-eating/purging presentation, vomiting or other compensatory behaviors can add fluid and electrolyte losses.
feeding behavior GO:0007631 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased feeding behavior (GO:0007631). GO:0007631 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Low Weight and Malnutrition Sustained energy restriction reduces body mass and produces chronic undernutrition.
Electrolyte and Volume Disturbance Electrolyte and volume abnormalities are context dependent and are not universal; purging and water-loading behaviors can substantially modify risk.
Show evidence (1 reference)
clinicaltrials:NCT03984344 SUPPORT Human Clinical
"Anorexia Nervosa (AN) is a life-threatening eating disorder characterised by an intense fear of weight gain and disturbed body image, which motivates severe dietary restriction or other weight loss behaviours (e.g. purging)."
The source directly supports restriction and other weight-loss behavior as defining AN events.
Low Weight and Malnutrition
The low-energy state is the established proximal driver of many endocrine, cardiovascular, gastrointestinal, skeletal, and brain-state consequences. It should not be mistaken for evidence that those downstream changes caused the initial psychiatric syndrome.
Neural state-and-trait model
Downstream
Low Body Weight and Weight Loss The malnourished low-energy state is expressed clinically as decreased body weight, often following substantial or rapid weight loss.
Hypoleptinemia Loss of adipose tissue and reduced energy intake lower the adipocyte-derived hormone leptin, producing the hypoleptinemia that signals the starved state.
Starvation-Adaptation Endocrine Response Chronic starvation elicits adaptive and maladaptive changes across gonadal, growth-hormone, adrenal, thyroid, and appetite-hormone axes.
Cardiovascular Adaptation and Instability Recent and rapid weight loss contributes to bradycardia and broader cardiovascular instability.
Gastrointestinal Dysmotility Disordered eating and malnutrition produce delayed gastric emptying and constipation that can complicate refeeding.
Undernutrition-Associated Brain Structural Changes A substantial component of widespread brain structural differences is associated with acute undernutrition and is smaller after partial weight restoration. Neural state-and-trait model
Show evidence (1 reference)
PMID:27811940 SUPPORT Human Clinical
"Anorexia nervosa is a psychiatric disorder characterized by altered body image, persistent food restriction and low body weight, and is associated with global endocrine dysregulation in both adolescent girls and women."
The review supports low weight as the clinical state associated with systemic endocrine consequences.
Starvation-Adaptation Endocrine Response
Chronic low energy alters hypothalamic-pituitary-gonadal, growth-hormone, adrenal, thyroid, leptin, ghrelin, and related endocrine axes. Many changes are adaptive to starvation, not validated diagnostic biomarkers.
endocrine cell CL:0000163 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves endocrine cell (CL:0000163). CL:0000163 is a cell type from the Cell Ontology.
response to starvation GO:0042594 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal response to starvation (GO:0042594). GO:0042594 is a biological process from the Gene Ontology. ⚠ ABNORMAL energy homeostasis GO:0097009 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal energy homeostasis (GO:0097009). GO:0097009 is a biological process from the Gene Ontology. ⚠ ABNORMAL hormone-mediated signaling pathway GO:0009755 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal hormone-mediated signaling pathway (GO:0009755). GO:0009755 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Hypogonadotropic Hypogonadism Hypothalamic-pituitary dysfunction suppresses gonadal hormone signaling.
Skeletal Integrity Loss Starvation-related endocrine changes and altered body composition impair bone accrual and maintenance.
Show evidence (1 reference)
DOI:10.3390/nu16132095 SUPPORT Human Clinical
"Our findings indicate that peripheral biomarkers may be linked to the pathophysiology of AN, such as processes of adaptation to starvation."
Meta-analysis supports a broad starvation-adaptation biomarker pattern while appropriately using associative language.
Hypogonadotropic Hypogonadism
Energy-deficit-associated hypothalamic-pituitary suppression reduces gonadal hormones. Amenorrhea is an important manifestation in some postmenarchal patients but is not required for a modern AN diagnosis.
hypothalamus UBERON:0001898 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in hypothalamus (UBERON:0001898). UBERON:0001898 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Amenorrhea Suppression of reproductive endocrine signaling can result in hypothalamic amenorrhea.
Show evidence (1 reference)
PMID:27811940 SUPPORT Human Clinical
"Dysfunction of the hypothalamic-pituitary axis includes hypogonadotropic hypogonadism with relative oestrogen and androgen deficiency"
The review directly supports the reproductive-axis mechanism.
Skeletal Integrity Loss
Low body mass, low fat and lean mass, amenorrhea, and endocrine adaptation reduce bone mineral density and increase later osteoporosis and fracture risk.
bone tissue UBERON:0002481 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in bone tissue (UBERON:0002481). UBERON:0002481 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Reduced Bone Mineral Density Impaired bone integrity is measured clinically as reduced bone mineral density across total body, spine, hip, and femur sites.
Show evidence (1 reference)
PMID:36401318 SUPPORT Human Clinical
"Lower bone mineral density (BMD) increases the risk of osteoporosis in individuals with eating disorders (EDs), particularly women with anorexia nervosa (AN), making them susceptible to pain and fractures throughout adulthood."
The review describes the clinically important skeletal consequence and its population context.
Cardiovascular Adaptation and Instability
Weight loss, autonomic adaptation, reduced cardiac mass, and electrolyte disturbances contribute to bradycardia, conduction disturbance, and arrhythmia risk. Not every patient has the same cardiovascular phenotype.
cardiovascular system UBERON:0004535 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in cardiovascular system (UBERON:0004535). UBERON:0004535 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Bradycardia Recent and rapid weight loss is strongly associated with severe bradycardia in hospitalized adolescents.
Arrhythmia AN can confer arrhythmia risk through several cardiac and electrolyte pathways.
Show evidence (1 reference)
DOI:10.1001/jamanetworkopen.2024.51094 SUPPORT Human Clinical
"Compared with the control group, the AN group had significantly higher risks of MACE (adjusted HR [AHR], 3.78; 95% CI, 2.83-5.05) and any cardiovascular condition (AHR, 1.93; 95% CI, 1.54-2.41)."
A national matched cohort quantifies increased cardiovascular risk but does not imply that every cardiovascular outcome is a starvation-only effect.
Electrolyte and Volume Disturbance
Restriction, purging, polydipsia, and renal adaptation can produce electrolyte and volume abnormalities. These are severity- and behavior-dependent complications rather than universal diagnostic signs.
Downstream
Hypokalemia Potassium depletion can occur, particularly with purging behaviors.
Hyponatremia Sodium disturbance can occur through reduced intake, volume regulation, or excessive water intake.
Arrhythmia Electrolyte imbalance can amplify arrhythmia risk, especially in medically unstable or purging presentations.
Show evidence (1 reference)
PMID:16721178 SUPPORT Human Clinical
"Nutritional abnormalities are also common, including sodium depletion and hypovolemia, hypophosphatemia and hypomagnesemia."
The review supports clinically important electrolyte and volume abnormalities in low-weight eating-disorder populations.
Gastrointestinal Dysmotility
Delayed gastric emptying and constipation occur in both AN presentations and can make nutritional rehabilitation uncomfortable; most changes improve with restoration of normal intake and body weight.
gastrointestinal tract UBERON:0005409 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in gastrointestinal tract, annotated with alimentary part of gastrointestinal system (UBERON:0005409). UBERON:0005409 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Constipation Gastrointestinal dysmotility manifests clinically as constipation.
Show evidence (1 reference)
PMID:16962383 SUPPORT Human Clinical
"Gastrointestinal disturbances develop secondary to the disordered eating behaviour and the concomitant malnutrition and subside mostly with the resumption of normal food intake and body weight."
The review supports both the secondary mechanism and reversibility with nutritional recovery.
Undernutrition-Associated Brain Structural Changes
Acute AN is associated with widespread reductions in cortical thickness and subcortical volume. Their relationship to low BMI and attenuation after partial weight restoration make them important state markers but not proof of a primary neural cause.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
brain UBERON:0000955 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in brain (UBERON:0000955). UBERON:0000955 is an anatomical location from the Uberon multi-species anatomy ontology.
Show evidence (1 reference)
PMID:36031441 SUPPORT Human Clinical
"In AN, reductions in cortical thickness, subcortical volumes, and, to a lesser extent, cortical surface area were sizable (Cohen's d up to 0.95), widespread, and colocalized with hub regions."
The multicenter analysis establishes the structural imaging state while the node description preserves causal uncertainty.
Immune and Microbiome Correlates
Cytokine and microbiome changes have been measured longitudinally in adolescents with AN. They remain correlates: this node has no causal downstream edge to depression, weight loss, or other phenotypes.
lymphocyte CL:0000542 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves lymphocyte (CL:0000542). CL:0000542 is a cell type from the Cell Ontology.
cytokine-mediated signaling pathway GO:0019221 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal cytokine-mediated signaling pathway (GO:0019221). GO:0019221 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Show evidence (1 reference)
DOI:10.3390/nu16111596 SUPPORT Human Clinical
"Relative to the HC group, serum levels of IL-1β and IL-6 were significantly lower during the acute phase (admission) of AN."
Longitudinal adolescent case-control data support an acute-phase cytokine association without resolving causal direction.
Hypoleptinemia
Low circulating leptin — the state — arising from loss of adipose (leptin-secreting) tissue during energy restriction. Hypoleptinemia is a core endocrine feature of the acute starved state, is the afferent signal for adaptation to starvation, and is the mechanistic target of recombinant-leptin (metreleptin) substitution. It arises from the upstream low-weight/malnutrition state modeled elsewhere in this graph.
Hypoleptinemia-driven starvation-induced hyperactivity
Adipocyte (leptin-secreting) CL:0000136 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Adipocyte (leptin-secreting), annotated with adipocyte (CL:0000136). CL:0000136 is a cell type from the Cell Ontology.
Leptin-mediated signaling pathway GO:0033210 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Leptin-mediated signaling pathway (GO:0033210). GO:0033210 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Hypogonadotropic Hypogonadism Hypoleptinemia removes a permissive signal for the reproductive axis, contributing to hypothalamic hypogonadism and amenorrhea; this is the leptin-specific mediator of the broader endocrine starvation response.
Excessive Physical Activity Low leptin is hypothesized to drive starvation-induced hyperactivity; the causal step is established in the ABA rodent model (via VTA STAT3 signaling) but only correlational (inverted-U) in humans, so this edge is carried under an emerging hypothesis rather than as an established human mechanism. Hypoleptinemia-driven starvation-induced hyperactivity
Show evidence (1 reference)
PMID:38303556 SUPPORT Other
"Hypoleptinemia as a core endocrine feature of AN serves as a central and peripheral trigger of tissue-specific adaptations to starvation."
Narrative review (no primary human data) establishes hypoleptinemia as the core endocrine trigger of starvation adaptation in anorexia nervosa.
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Anorexia Nervosa Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

13
Cardiovascular 2
Bradycardia HP:0001662 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Bradycardia (HP:0001662). HP:0001662 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34418241 SUPPORT Human Clinical
"Forty-eight percent of the AN patient admissions were due to severe bradycardia (AN-B+ group)."
The estimate is explicitly confined to a hospitalized adolescent cohort; no KB-wide frequency band is inferred.
Arrhythmia HP:0011675 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Arrhythmia (HP:0011675). HP:0011675 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:16721178 SUPPORT Human Clinical
"Acrocyanosis is common, and patients with anorexia nervosa are at risk of various arrhythmias."
The medical-complications review directly identifies arrhythmia risk.
Digestive 1
Constipation HP:0002019 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Constipation (HP:0002019). HP:0002019 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:16962383 SUPPORT Human Clinical
"Both anorexia nervosa subtypes experience substantial delays in gastric emptying as well as constipation."
The review directly supports constipation in both AN presentations.
Genitourinary 1
Amenorrhea HP:0000141 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypothalamic amenorrhea in postmenarchal patients, annotated with Amenorrhea (HP:0000141). HP:0000141 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:36401318 SUPPORT Human Clinical
"In AN, low weight, hypothalamic amenorrhoea, and longer illness duration are established risk factors for low BMD"
The systematic review explicitly identifies hypothalamic amenorrhea in females with AN.
Metabolism 2
Hypokalemia HP:0002900 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypokalemia (HP:0002900). HP:0002900 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40048192 SUPPORT Human Clinical
"These disorders may be associated with changes in weight, electrolyte abnormalities (eg, hyponatremia, hypokalemia), bradycardia, disturbances in reproductive hormones (eg, decreased estradiol levels in females), and decreased bone density."
The review includes AN among eating disorders with hypokalemia while the phenotype context avoids implying universality.
Hyponatremia HP:0002902 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hyponatremia (HP:0002902). HP:0002902 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:27811940 SUPPORT Human Clinical
"Dysfunction of the hypothalamic-pituitary axis includes hypogonadotropic hypogonadism with relative oestrogen and androgen deficiency, growth hormone resistance, hypercortisolaemia, non-thyroidal illness syndrome, hyponatraemia and hypooxytocinaemia."
The endocrine review explicitly includes hyponatremia among AN-associated disturbances.
Musculoskeletal 1
Reduced Bone Mineral Density HP:0004349 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Reduced bone mineral density (HP:0004349). HP:0004349 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:36401318 SUPPORT Human Clinical
"BMD in individuals with AN (total body, spine, hip, and femur), with BN (total body and spine) and with OSFED (spine) was lower than in HC."
Meta-analysis of female cohorts confirms lower BMD across multiple sites in AN.
Nervous System 4
Abnormal Eating Behavior HP:0100738 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Restrictive eating and weight-gain-interfering behavior, annotated with Abnormal eating behavior (HP:0100738). HP:0100738 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
clinicaltrials:NCT03984344 SUPPORT Human Clinical
"Anorexia Nervosa (AN) is a life-threatening eating disorder characterised by an intense fear of weight gain and disturbed body image, which motivates severe dietary restriction or other weight loss behaviours (e.g. purging)."
The source directly describes the diagnostic psychopathology and restrictive behavior.
Anxiety HP:0000739 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Anxiety (HP:0000739). HP:0000739 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
DOI:10.1007/s00115-025-01820-y SUPPORT Human Clinical
"It is frequently associated with other psychiatric disorders, such as depression, anxiety and obsessive-compulsive disorders as well as numerous physical complications."
The clinical update identifies anxiety as a frequent comorbidity.
Depression HP:0000716 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Depression (HP:0000716). HP:0000716 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40048192 SUPPORT Human Clinical
"Individuals with anorexia nervosa, bulimia nervosa, and binge-eating disorder have high lifetime rates of depression (76.3% for bulimia nervosa, 65.5% for binge-eating disorder, and 49.5% for anorexia nervosa) and higher rates of suicide attempts than those without eating disorders."
The review provides an AN-specific lifetime depression estimate.
Excessive Physical Activity Hyperactivity HP:0000752 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Excessive physical activity / motor restlessness, annotated with Hyperactivity (HP:0000752). HP:0000752 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31156489 SUPPORT Human Clinical
"an inverted U-shaped relationship has been observed between their serum leptin levels and physical activity."
Human data document an inverted-U association between serum leptin and physical activity in AN, supporting hyperactivity as a leptin-linked manifestation.
Growth 1
Low Body Weight and Weight Loss Decreased body weight HP:0004325 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Significantly low body weight and weight loss, annotated with Decreased body weight (HP:0004325). HP:0004325 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34418241 SUPPORT Human Clinical
"Patients in this group had a higher maximum lifetime weight (P = 0.0045), greater premorbid weight loss (P = 0.0011), and more rapid weight loss (P = 0.0001)."
Hospitalized adolescent data document clinically consequential recent weight loss in AN.
Other 1
Obsessive-Compulsive Trait HP:0008770 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Obsessive-compulsive trait (HP:0008770). HP:0008770 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
DOI:10.1007/s00115-025-01820-y SUPPORT Human Clinical
"It is frequently associated with other psychiatric disorders, such as depression, anxiety and obsessive-compulsive disorders as well as numerous physical complications."
The update supports obsessive-compulsive comorbidity but does not quantify the broader trait in all patients, so support is partial.
🧬

Genetic Associations

1
Polygenic common-variant susceptibility (Complex polygenic susceptibility; no single sufficient gene is asserted)
relationship_type: SUSCEPTIBILITY variant_origin: GERMLINE
Show evidence (1 reference)
PMID:31308545 SUPPORT Human Clinical
"Here we combine data from the Anorexia Nervosa Genetics Initiative (ANGI)8,9 and the Eating Disorders Working Group of the Psychiatric Genomics Consortium (PGC-ED) and conduct a genome-wide association study of 16,992 cases of anorexia nervosa and 55,525 controls, identifying eight significant loci."
Large GWAS evidence supports common germline susceptibility loci without establishing any single-gene cause.
💊

Medical Actions

6
Nutritional rehabilitation and monitored weight restoration
Category: Therapeutic Action: dietary interventionNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is dietary intervention (NCIT:C15447). NCIT:C15447 is a clinical intervention from the NCI Thesaurus. Ontology label: Dietary Intervention NCIT:C15447
Nutritional support and gradual, monitored weight restoration address the low-energy state and medical complications. Refeeding intensity and electrolyte monitoring must be individualized because severely malnourished patients can decompensate during refeeding; DisMech does not prescribe a patient-level protocol.
Mechanism Target:
RESTORES Low Weight and Malnutrition — Nutritional rehabilitation restores energy availability and body weight, allowing many starvation-adaptation changes to reverse.
Show evidence (1 reference)
PMID:27811940 SUPPORT Human Clinical
"Although most, but not all, of these endocrine disturbances are adaptive to the low energy state of chronic starvation and reverse with treatment of the eating disorder"
The endocrine review supports reversal of many low-energy adaptations with treatment while not claiming universal reversibility.
Target Phenotypes: Decreased body weight HP:0004325 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Decreased body weight (HP:0004325). HP:0004325 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40048192 SUPPORT Human Clinical
"First-line treatments for eating disorders include nutritional support, psychotherapy, and pharmacotherapy."
The review identifies nutritional support as a first-line component of eating-disorder care; the AN-specific rationale is weight restoration.
Family-based treatment for youth
Category: Therapeutic Action: Family TherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Family Therapy (NCIT:C93347). NCIT:C93347 is a clinical intervention from the NCI Thesaurus. NCIT:C93347
Family-based treatment with parental oversight of eating has the strongest comparative evidence in youth with AN. The age context is essential and the result should not be generalized to all adults or severe enduring illness.
Mechanism Target:
MODULATES Restrictive-Eating Psychopathology — Parental oversight and structured support modify restrictive eating behavior and facilitate weight restoration; this is a behavioral target, not proof of a molecular mechanism.
Show evidence (1 reference)
PMID:40048192 SUPPORT Human Clinical
"Youth with anorexia nervosa benefit from family-based treatment with parental oversight of eating, resulting in a remission rate at 6 to 12 months of 48.6% vs 34.3% with individual treatment (odds ratio, 2.08; 95% CI, 1.07-4.03; P = .03)."
Comparative youth data support behavioral modulation through parental oversight of eating.
Target Phenotypes: Abnormal eating behavior HP:0100738 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Abnormal eating behavior (HP:0100738). HP:0100738 is a phenotype from the Human Phenotype Ontology. Decreased body weight HP:0004325 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Decreased body weight (HP:0004325). HP:0004325 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40048192 SUPPORT Human Clinical
"Youth with anorexia nervosa benefit from family-based treatment with parental oversight of eating, resulting in a remission rate at 6 to 12 months of 48.6% vs 34.3% with individual treatment (odds ratio, 2.08; 95% CI, 1.07-4.03; P = .03)."
The evidence is AN-specific and explicitly limited to youth.
Eating-disorder-focused cognitive behavioral therapy
Category: Therapeutic Action: cognitive behavior therapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is cognitive behavior therapy (NCIT:C64345). NCIT:C64345 is a clinical intervention from the NCI Thesaurus. Ontology label: Cognitive Behavior Therapy NCIT:C64345
Eating-disorder-focused CBT is one of several recommended psychotherapies. Selection depends on age, illness duration, comorbidity, prior treatment, and patient preference; it is not presented as uniformly superior.
Target Phenotypes: Abnormal eating behavior HP:0100738 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Abnormal eating behavior (HP:0100738). HP:0100738 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
DOI:10.1007/s00115-025-01820-y SUPPORT Human Clinical
"The treatment of choice for AN includes cognitive behavioral therapy and family-based therapy for children and adolescents."
The clinical update supports CBT while the entry preserves age and treatment-selection context.
Olanzapine adjunct for weight gain
Category: Therapeutic Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: olanzapine CHEBI:7735 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses olanzapine (CHEBI:7735). CHEBI:7735 is a therapeutic agent from Chemical Entities of Biological Interest.
Olanzapine may be considered as an adjunct for weight gain in selected patients. Evidence is moderate, it is not a stand-alone treatment, and broad psychopharmacotherapy efficacy in AN has not been established.
Target Phenotypes: Decreased body weight HP:0004325 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Decreased body weight (HP:0004325). HP:0004325 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
DOI:10.1007/s00115-025-01820-y SUPPORT Human Clinical
"With the exception of moderate evidence supporting the use of olanzapine regarding weight gain, there is currently no evidence for the efficacy of psychopharmacotherapy in AN."
The update supports a narrowly calibrated adjunctive weight-gain claim and cautions against general medication efficacy.
Inpatient medical and psychiatric stabilization
Category: Therapeutic Action: supportive careNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is supportive care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. Ontology label: Supportive Care NCIT:C15747
Hospital-level supportive care is indicated for serious medical or psychiatric complications such as severe bradycardia or suicidality. Admission decisions are individualized; this entry does not define bedside thresholds.
Target Phenotypes: Bradycardia HP:0001662 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Bradycardia (HP:0001662). HP:0001662 is a phenotype from the Human Phenotype Ontology. Arrhythmia HP:0011675 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Arrhythmia (HP:0011675). HP:0011675 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40048192 SUPPORT Human Clinical
"Individuals with serious medical or psychiatric complications of eating disorders such as bradycardia or suicidality should be hospitalized for treatment."
The review directly supports hospitalization for serious complications, including bradycardia and suicidality.
Metreleptin (recombinant human leptin)
Category: Therapeutic Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: metreleptin NCIT:C170171 NCI Thesaurus (NCIT) Relation: this treatment uses this therapeutic agent This treatment uses metreleptin (NCIT:C170171). NCIT:C170171 is a therapeutic agent from the NCI Thesaurus.
Metreleptin, a recombinant human leptin analogue, has been used off-label in small uncontrolled case series of severely ill, hyperactive patients with AN, with reports of rapid improvement in depression, eating-disorder cognitions, weight phobia, and hyperactivity. It is a mechanism-directed substitution for the hypoleptinemia of AN. It is NOT approved for AN (metreleptin is approved only for generalized lipodystrophy); the evidence is uncontrolled and the authors uniformly call for randomized placebo-controlled trials.
Mechanism Target:
RESTORES Hypoleptinemia — Metreleptin substitutes for the deficient leptin signal, directly targeting the hypoleptinemia that drives the starvation-adaptation state.
Show evidence (1 reference)
PMID:38303556 SUPPORT Other
"may induce a profound alleviation of the complex symptomatology of patients with anorexia nervosa (AN)"
Review reports that recombinant-leptin substitution can profoundly alleviate AN symptomatology, consistent with correcting the hypoleptinemia.
Target Phenotypes: Excessive physical activity HP:0000752 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Excessive physical activity, annotated with Hyperactivity (HP:0000752). HP:0000752 is a phenotype from the Human Phenotype Ontology. Depression HP:0000716 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Depression (HP:0000716). HP:0000716 is a phenotype from the Human Phenotype Ontology.
Show evidence (5 references)
PMID:32855384 SUPPORT Human Clinical
"Surprisingly, depression improved rapidly in all patients."
The first off-label AN case series reports rapid depression improvement; uncontrolled, so support is partial.
PMID:36349765 SUPPORT Human Clinical
"was associated with self-reported increments of appetite and hunger resulting in rapid weight gain and substantial improvement of eating disorder cognitions and of depression."
Single-case report of appetite, weight, cognition, and depression improvement during metreleptin; uncontrolled.
PMID:33966118 SUPPORT Human Clinical
"underscore the need for a double-blind placebo-controlled trial to confirm the observed strong, multiple and rapid onset beneficial effects of metreleptin in AN."
Male-adolescent case report extends the observed effects and explicitly calls for controlled trials.
+ 2 more references
🔬

Biochemical Markers

2
Hypoleptinemia (DECREASED)
Pathograph Readouts
Readout Of Hypoleptinemia Negative Monitoring
Low serum leptin is a direct readout of the Hypoleptinemia mechanism node and indexes the severity of the starvation-adaptation state; it partially normalizes with weight restoration and is the pharmacodynamic target of metreleptin substitution.
Show evidence (2 references)
PMID:31156489 SUPPORT Other
"Hypoleptinemia acts as a key trigger for the adaptation to starvation by affecting diverse brain regions including the reward system"
The review identifies hypoleptinemia as the central endocrine feature and trigger of starvation adaptation in AN.
PMID:38303556 SUPPORT Other
"Hypoleptinemia as a core endocrine feature of AN serves as a central and peripheral trigger of tissue-specific adaptations to starvation."
Narrative review (no primary human data) confirms hypoleptinemia as a core, characteristic endocrine feature of anorexia nervosa.
Elevated Soluble Leptin Receptor (INCREASED)
Show evidence (1 reference)
DOI:10.3390/nu16132095 SUPPORT Human Clinical
"soluble leptin receptor levels were significantly higher in cases of AN compared with those in non-AN controls"
Wu et al. 2024 meta-analysis of 52 peripheral biomarkers identifies sOB-R elevation as a robust finding across multiple AN cohorts.
🔬

Diagnosis

4
Clinical eating-disorder assessment (Diagnosis is clinical: persistent energy restriction and significantly low body weight are evaluated together with fear of weight gain or persistent weight-gain-interfering behavior and disturbance in body-weight or shape experience. Motivation and developmental context matter, and no peripheral biomarker establishes the diagnosis.)
clinical assessment NCIT:C124351 NCI Thesaurus (NCIT)
Show evidence (1 reference)
DOI:10.1038/s41398-023-02585-1 SUPPORT Human Clinical
"Anorexia nervosa (AN) is an eating disorder characterized by restricted energy intake, abnormally low body weight, intense fear of weight-gain, and body image disturbances [ 1]."
The source succinctly states the core clinical phenotype used for diagnostic assessment.
Nutritional, electrolyte, and endocrine assessment (Weight trajectory, intake, hydration, electrolytes, renal and hepatic function, blood counts, and endocrine complications are assessed according to illness severity and behavior context. Normal absolute weight does not exclude risk from rapid recent loss.)
nutrition assessment NCIT:C124351 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:40048192 SUPPORT Human Clinical
"These disorders may be associated with changes in weight, electrolyte abnormalities (eg, hyponatremia, hypokalemia), bradycardia, disturbances in reproductive hormones (eg, decreased estradiol levels in females), and decreased bone density."
The review identifies the medical domains requiring assessment.
Cardiovascular assessment and electrocardiography (Pulse, blood pressure, symptoms, and electrocardiography are evaluated when bradycardia, conduction disturbance, electrolyte abnormality, syncope, or other medical instability is suspected.)
electrocardiography NCIT:C38053 NCI Thesaurus (NCIT)
Show evidence (1 reference)
DOI:10.1001/jamanetworkopen.2024.51094 SUPPORT Human Clinical
"Clinicians should monitor comorbid cardiovascular conditions among patients with AN at initial presentation, during treatment, and at follow-up."
National cohort findings support cardiovascular monitoring across the care trajectory.
Peripheral biomarkers are investigational (Endocrine, metabolic, and immune markers differ between AN and controls in research studies but are not validated as stand-alone diagnostic tests.)
clinical assessment NCIT:C124351 NCI Thesaurus (NCIT)
Show evidence (1 reference)
DOI:10.3390/nu16132095 SUPPORT Human Clinical
"However, reliable biomarkers for AN have yet to be established."
The meta-analysis explicitly cautions against treating measured peripheral differences as established diagnostic biomarkers.
📈

Progression

2
Acute underweight illness
Acute undernutrition can produce widespread structural brain differences; their smaller magnitude after partial weight restoration argues that at least part of this imaging phenotype is state dependent.
Show evidence (1 reference)
PMID:36031441 SUPPORT Human Clinical
"Highlighting the effects of undernutrition, these deficits were associated with lower body mass index in the AN sample and were less pronounced in partially weight-restored patients."
Multicenter imaging data demonstrate illness-state dependence of brain structural findings.
Long-term recovery and relapse
Recovery may occur even after many years, but persistent illness, relapse, and AN-related death occur in long-term cohorts; one historical treated cohort should not be generalized as a contemporary population estimate.
Show evidence (1 reference)
PMID:11459385 SUPPORT Human Clinical
"Recovery is still possible for anorexic patients after a period of 21 years. On the other hand, patients can relapse, becoming symptomatic again despite previously achieving recovery status."
The prospective 21-year cohort directly supports a heterogeneous, potentially relapsing long-term course.
📊

Prevalence

2
females worldwide
Lifetime Prevalence 620.0 per 100,000 >1 in 1,000
Sex-stratified estimate from the 2023 genetic study introduction; this replaces the prior any-eating-disorder estimate, which was outside the scope of the AN entry.
Show evidence (1 reference)
DOI:10.1038/s41398-023-02585-1 SUPPORT Human Clinical
"The estimated lifetime preva- lence is 0.62% among females and 0.04% among males"
The female estimate converts to 620 cases per 100,000.
males worldwide
Lifetime Prevalence 40.0 per 100,000 1–9 per 10,000
Sex-stratified estimate from the 2023 genetic study introduction; male AN is less common but remains within the scope of this disease concept.
Show evidence (1 reference)
DOI:10.1038/s41398-023-02585-1 SUPPORT Human Clinical
"The estimated lifetime preva- lence is 0.62% among females and 0.04% among males"
The male estimate converts to 40 cases per 100,000.
⚖️

Clinical Burden

High
AN can cause multi-organ medical instability, prolonged disability, hospitalization, relapse, and excess mortality, including suicide-related mortality. Burden varies by illness phase, but the potential need for intensive multidisciplinary care supports a high disease-level rating.
Show evidence (1 reference)
PMID:40048192 SUPPORT Human Clinical
"Anorexia nervosa is associated with a mortality rate of 5.1 deaths per 1000 person-years (95% CI, 4.0-6.1), nearly 6 times higher than that of individuals of the same age without anorexia nervosa; 25% of deaths among individuals with anorexia nervosa are from suicide."
The review quantifies the excess mortality that contributes to AN's high clinical burden.
🔀

Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from Anorexia Nervosa:

Avoidant/restrictive food intake disorder MONDO:7770002
Overlapping Features ARFID can involve restriction and low weight, but the restriction is not driven by the AN pattern of weight-gain fear or body-weight/shape disturbance. Psychological motivation and developmental context are therefore central to differentiation.
Show evidence (1 reference)
DOI:10.1111/jep.13586 SUPPORT Other
"At least with present day medical and scientific knowledge, a complete characterization of the AN phenotype cannot be achieved without reference to psychological states of motivation."
The conceptual analysis supports the importance of motivation for AN boundaries but does not itself provide a direct ARFID comparison.
Bulimia nervosa MONDO:0005452
Overlapping Features Bulimia nervosa can share binge eating and purging but does not require the persistently low body-weight state that defines AN. AN's binge-eating/purging presentation remains within this parent AN entry.
Show evidence (1 reference)
PMID:40048192 SUPPORT Human Clinical
"Common eating disorders include anorexia nervosa, bulimia nervosa, binge-eating disorder, and avoidant/restrictive food intake disorder."
The review establishes these as distinct common eating disorders; the weight-based distinction is clinical interpretation and support is marked partial.
📊

Related Datasets

3
Genome-wide association study identifies eight risk loci and implicates metabo-psychiatric origins for anorexia nervosa PMID:31308545
Anorexia Nervosa Genetics Initiative and Psychiatric Genomics Consortium GWAS meta-analysis of common-variant susceptibility and cross-trait genetic correlations.
Homo sapiens n=72517
Conditions: anorexia nervosa controls
Findings
Eight genome-wide significant loci and cross-trait correlations support polygenic metabo-psychiatric susceptibility.
Show evidence (1 reference)
PMID:31308545 SUPPORT Human Clinical
"The genetic architecture of anorexia nervosa mirrors its clinical presentation, showing significant genetic correlations with psychiatric disorders, physical activity, and metabolic (including glycemic), lipid and anthropometric traits, independent of the effects of common variants associated..."
The finding captures the study's metabo-psychiatric genetic result without assigning causality to individual genes.
PMID:31308545
Show evidence (1 reference)
PMID:31308545 SUPPORT Human Clinical
"Here we combine data from the Anorexia Nervosa Genetics Initiative (ANGI)8,9 and the Eating Disorders Working Group of the Psychiatric Genomics Consortium (PGC-ED) and conduct a genome-wide association study of 16,992 cases of anorexia nervosa and 55,525 controls, identifying eight significant loci."
The publication reports 72,517 total analyzed cases and controls.
Peripheral Biomarkers of Anorexia Nervosa: A Meta-Analysis DOI:10.3390/nu16132095
Random-effects meta-analysis comparing 52 peripheral biomarkers in AN and non-AN groups across endocrine, metabolic, immune, and growth axes.
Homo sapiens
Conditions: anorexia nervosa non-AN comparison groups
Findings
Multiple endocrine and metabolic biomarkers differ between AN and non-AN groups, consistent with starvation adaptation but not diagnostic specificity.
Show evidence (1 reference)
DOI:10.3390/nu16132095 SUPPORT Human Clinical
"Our findings indicate that peripheral biomarkers may be linked to the pathophysiology of AN, such as processes of adaptation to starvation."
The authors explicitly use associative language and interpret the finding as adaptation to starvation.
DOI:10.3390/nu16132095
Show evidence (1 reference)
DOI:10.3390/nu16132095 SUPPORT Human Clinical
"We conducted two-level random-effects meta-analyses to examine the difference between AN and comparison groups across 52 distinct biomarkers"
The abstract describes the dataset scope and analysis design.
Incidence and Risk of Cardiovascular Outcomes in Patients With Anorexia Nervosa DOI:10.1001/jamanetworkopen.2024.51094
Taiwan national health-insurance matched cohort comparing cardiovascular outcomes in patients with AN and propensity-matched controls.
Homo sapiens n=22891
Conditions: anorexia nervosa matched controls
Findings
AN was associated with higher risk of major adverse cardiovascular events and any cardiovascular condition in this matched national cohort.
Show evidence (1 reference)
DOI:10.1001/jamanetworkopen.2024.51094 SUPPORT Human Clinical
"Compared with the control group, the AN group had significantly higher risks of MACE (adjusted HR [AHR], 3.78; 95% CI, 2.83-5.05) and any cardiovascular condition (AHR, 1.93; 95% CI, 1.54-2.41)."
The matched cohort quantifies cardiovascular association; it does not establish a single causal pathway for every outcome.
DOI:10.1001/jamanetworkopen.2024.51094
Show evidence (1 reference)
DOI:10.1001/jamanetworkopen.2024.51094 SUPPORT Human Clinical
"The study population included 2081 patients with AN and 20 810 matched controls, for a total of 22 891 participants (mean [SD] age, 24.9 [9.9] years; 91.3% female)."
The cohort composition supports the recorded sample count and population context.
🔬

Clinical Trials

1
NCT06305182 PHASE_II RECRUITING
Randomized placebo-controlled trial of metreleptin in anorexia nervosa, evaluating effects on depressive symptoms and concomitant changes in brain connectivity — the controlled trial the uncontrolled metreleptin case series uniformly called for.
Target Phenotypes: Depression HP:0000716 Human Phenotype Ontology (HP) Relation: this clinical trial targets this phenotype This clinical trial targets Depression (HP:0000716). HP:0000716 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
clinicaltrials:NCT06305182 SUPPORT Human Clinical
"This study tests the effect of metreleptin in comparison with placebo"
Registered randomized controlled trial testing metreleptin versus placebo in AN, directly addressing the RCT gap noted throughout the case-series evidence.
{ }

Source YAML

click to show 
name: Anorexia Nervosa
creation_date: "2026-04-24T20:56:38Z"
category: Psychiatric
description: >-
  Anorexia nervosa is a serious eating disorder defined by persistent energy
  restriction leading to significantly low body weight, together with intense
  fear of weight gain or persistent behavior that interferes with weight gain
  and disturbance in body-weight or shape experience. This parent entry covers
  both restricting and binge-eating/purging presentations. It distinguishes
  the established physiological consequences of undernutrition from proposed
  upstream neural, metabolic, immune, and microbiome mechanisms.
disease_term:
  preferred_term: anorexia nervosa
  term:
    id: MONDO:0005351
    label: anorexia nervosa
parents:
- Eating Disorder
- Mental Health Disorder
has_subtypes:
- name: Restricting
  display_name: Restricting presentation
  description: >-
    Presentation without recurrent binge eating or purging during the relevant
    diagnostic interval.
  evidence:
  - reference: PMID:16962383
    reference_title: "Gastrointestinal disturbances in eating disorders: clinical and neurobiological aspects."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Studies focusing on general outcome and medical comorbidity describe a
      worse outcome in the binge eating/purging subtype of anorexia nervosa
      compared to the restricting subtype.
    explanation: >-
      The review explicitly distinguishes the restricting presentation from
      the binge-eating/purging presentation.
- name: Binge-eating/purging
  display_name: Binge-eating/purging presentation
  description: >-
    Presentation with recurrent binge eating or purging during the relevant
    diagnostic interval; purging-related electrolyte complications require
    separate clinical attention.
  evidence:
  - reference: PMID:16962383
    reference_title: "Gastrointestinal disturbances in eating disorders: clinical and neurobiological aspects."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Studies focusing on general outcome and medical comorbidity describe a
      worse outcome in the binge eating/purging subtype of anorexia nervosa
      compared to the restricting subtype.
    explanation: >-
      The review explicitly distinguishes the binge-eating/purging
      presentation from the restricting presentation.
prevalence:
- population: females worldwide
  measure_type: LIFETIME_PREVALENCE
  prevalence_class: ABOVE_1_IN_1000
  rate_per_100000: 620.0
  notes: >-
    Sex-stratified estimate from the 2023 genetic study introduction; this
    replaces the prior any-eating-disorder estimate, which was outside the
    scope of the AN entry.
  evidence:
  - reference: DOI:10.1038/s41398-023-02585-1
    reference_title: Genome-wide analysis of anorexia nervosa and major psychiatric disorders and related traits reveals genetic overlap and identifies novel risk loci for anorexia nervosa
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: |-
      The estimated lifetime preva-
      lence is 0.62% among females and 0.04% among males
    explanation: >-
      The female estimate converts to 620 cases per 100,000.
- population: males worldwide
  measure_type: LIFETIME_PREVALENCE
  prevalence_class: BAND_1_5_PER_10000
  rate_per_100000: 40.0
  notes: >-
    Sex-stratified estimate from the 2023 genetic study introduction; male AN
    is less common but remains within the scope of this disease concept.
  evidence:
  - reference: DOI:10.1038/s41398-023-02585-1
    reference_title: Genome-wide analysis of anorexia nervosa and major psychiatric disorders and related traits reveals genetic overlap and identifies novel risk loci for anorexia nervosa
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: |-
      The estimated lifetime preva-
      lence is 0.62% among females and 0.04% among males
    explanation: >-
      The male estimate converts to 40 cases per 100,000.
clinical_burden:
  burden_level: HIGH
  rationale: >-
    AN can cause multi-organ medical instability, prolonged disability,
    hospitalization, relapse, and excess mortality, including suicide-related
    mortality. Burden varies by illness phase, but the potential need for
    intensive multidisciplinary care supports a high disease-level rating.
  evidence:
  - reference: PMID:40048192
    reference_title: "Eating Disorders: A Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Anorexia nervosa is associated with a mortality rate of 5.1 deaths per
      1000 person-years (95% CI, 4.0-6.1), nearly 6 times higher than that of
      individuals of the same age without anorexia nervosa; 25% of deaths among
      individuals with anorexia nervosa are from suicide.
    explanation: >-
      The review quantifies the excess mortality that contributes to AN's high
      clinical burden.
progression:
- phase: Acute underweight illness
  notes: >-
    Acute undernutrition can produce widespread structural brain differences;
    their smaller magnitude after partial weight restoration argues that at
    least part of this imaging phenotype is state dependent.
  evidence:
  - reference: PMID:36031441
    reference_title: "Brain Structure in Acutely Underweight and Partially Weight-Restored Individuals With Anorexia Nervosa: A Coordinated Analysis by the ENIGMA Eating Disorders Working Group."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Highlighting the effects of undernutrition, these deficits were associated
      with lower body mass index in the AN sample and were less pronounced in
      partially weight-restored patients.
    explanation: >-
      Multicenter imaging data demonstrate illness-state dependence of brain
      structural findings.
- phase: Long-term recovery and relapse
  notes: >-
    Recovery may occur even after many years, but persistent illness, relapse,
    and AN-related death occur in long-term cohorts; one historical treated
    cohort should not be generalized as a contemporary population estimate.
  evidence:
  - reference: PMID:11459385
    reference_title: Long-term outcome of anorexia nervosa in a prospective 21-year follow-up study.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Recovery is still possible for anorexic patients after a period of 21
      years. On the other hand, patients can relapse, becoming symptomatic again
      despite previously achieving recovery status.
    explanation: >-
      The prospective 21-year cohort directly supports a heterogeneous,
      potentially relapsing long-term course.
inheritance:
- name: Polygenic inheritance
  inheritance_term:
    preferred_term: Polygenic inheritance
    term:
      id: HP:0010982
      label: Polygenic inheritance
  description: >-
    AN has substantial heritability and a common-variant architecture; it is not
    modeled as a Mendelian disorder.
  evidence:
  - reference: PMID:31308545
    reference_title: Genome-wide association study identifies eight risk loci and implicates metabo-psychiatric origins for anorexia nervosa.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Characterized primarily by a low body-mass index, anorexia nervosa is a
      complex and serious illness1, affecting 0.9-4% of women and 0.3% of men2-4,
      with twin-based heritability estimates of 50-60%5.
    explanation: >-
      The GWAS report summarizes twin heritability and then identifies multiple
      common-variant loci, supporting polygenic rather than Mendelian
      inheritance.
genetic:
- name: Polygenic common-variant susceptibility
  association: Complex polygenic susceptibility; no single sufficient gene is asserted
  relationship_type: SUSCEPTIBILITY
  variant_origin: GERMLINE
  notes: >-
    Genome-wide significant loci and genetic correlations establish inherited
    susceptibility at the population level. Individual nearby genes are not
    represented as causative because locus-to-gene assignment and mechanistic
    mediation remain uncertain.
  evidence:
  - reference: PMID:31308545
    reference_title: Genome-wide association study identifies eight risk loci and implicates metabo-psychiatric origins for anorexia nervosa.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we combine data from the Anorexia Nervosa Genetics Initiative
      (ANGI)8,9 and the Eating Disorders Working Group of the Psychiatric
      Genomics Consortium (PGC-ED) and conduct a genome-wide association study
      of 16,992 cases of anorexia nervosa and 55,525 controls, identifying eight
      significant loci.
    explanation: >-
      Large GWAS evidence supports common germline susceptibility loci without
      establishing any single-gene cause.
mechanistic_hypotheses:
- hypothesis_group_id: leptin_hyperactivity
  hypothesis_label: Hypoleptinemia-driven starvation-induced hyperactivity
  status: EMERGING
  description: >-
    The hypothesis that low circulating leptin is a causal driver of the
    physical hyperactivity and motor restlessness of AN, not merely a
    correlate. The causal step is demonstrated in the rodent activity-based
    anorexia (ABA) model, where recombinant leptin suppresses
    semi-starvation-induced hyperactivity; human evidence is correlational (an
    inverted U-shaped leptin-activity relationship) and inconsistent, so the
    causal claim is retained as emerging pending controlled human testing.
  evidence:
  - reference: PMID:31156489
    reference_title: "Clinical Trials Required to Assess Potential Benefits and Side Effects of Treatment of Patients With Anorexia Nervosa With Recombinant Human Leptin."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      the rat model activity-based anorexia (ABA) convincingly demonstrates the
      pivotal role of hypoleptinemia in the development of starvation-induced
      hyperactivity.
    explanation: >-
      The ABA rodent model provides the primary causal evidence linking
      hypoleptinemia to starvation-induced hyperactivity; human confirmation is
      still lacking, which is why this group is EMERGING.
- hypothesis_group_id: metabo_psychiatric_liability
  hypothesis_label: Polygenic metabo-psychiatric liability
  status: CANONICAL
  description: >-
    Common-variant liability spans psychiatric, physical-activity, metabolic,
    lipid, and anthropometric traits. This is a robust genetic architecture,
    but the intermediate molecular and circuit mechanisms leading to
    restrictive eating remain unresolved.
  evidence:
  - reference: PMID:31308545
    reference_title: Genome-wide association study identifies eight risk loci and implicates metabo-psychiatric origins for anorexia nervosa.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The genetic architecture of anorexia nervosa mirrors its clinical
      presentation, showing significant genetic correlations with psychiatric
      disorders, physical activity, and metabolic (including glycemic), lipid
      and anthropometric traits, independent of the effects of common variants
      associated with body-mass index.
    explanation: >-
      GWAS genetic correlations support a metabo-psychiatric susceptibility
      model while not identifying a direct causal mediator.
- hypothesis_group_id: neural_state_trait_model
  hypothesis_label: Neural state-and-trait model
  status: EMERGING
  description: >-
    Structural and functional brain alterations may include both trait-like
    vulnerabilities and consequences of acute undernutrition. Imaging
    association alone cannot determine which changes initiate restrictive
    eating, so this model is kept separate from the established starvation
    cascade.
  evidence:
  - reference: PMID:34296492
    reference_title: "Structural and functional brain alterations in anorexia nervosa:A multimodal meta-analysis of neuroimaging studies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This multimodal meta-analysis identified reductions of gray matter and
      functional activity in the anterior and median cingulate in patients with
      AN, which contributes to further understanding of the pathophysiology of
      AN.
    explanation: >-
      Multimodal case-control imaging supports reproducible neural correlates.
  - reference: PMID:36031441
    reference_title: "Brain Structure in Acutely Underweight and Partially Weight-Restored Individuals With Anorexia Nervosa: A Coordinated Analysis by the ENIGMA Eating Disorders Working Group."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Highlighting the effects of undernutrition, these deficits were associated
      with lower body mass index in the AN sample and were less pronounced in
      partially weight-restored patients.
    explanation: >-
      Weight-state dependence limits causal interpretation of brain structural
      differences as primary disease drivers.
- hypothesis_group_id: immune_microbiome_correlates
  hypothesis_label: Immune and microbiome correlates
  status: EMERGING
  description: >-
    Cytokine and microbiome differences have been observed during acute illness
    and recovery, but current human studies are associative and do not establish
    whether these changes initiate, maintain, or merely reflect starvation.
  evidence:
  - reference: DOI:10.3390/nu16111596
    reference_title: Cytokine and Microbiome Changes in Adolescents with Anorexia Nervosa at Admission, Discharge, and One-Year Follow-Up
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We found associations between cytokines and bodyweight, illness duration,
      depressive symptoms, and the microbiome.
    explanation: >-
      Longitudinal adolescent data support correlated immune and microbiome
      changes, not a demonstrated causal direction.
pathophysiology:
- name: Polygenic Metabo-Psychiatric Susceptibility
  description: >-
    Common germline variation contributes distributed susceptibility across
    psychiatric and metabolic trait domains. The node does not assert a single
    causal gene or a known molecular route to AN.
  mechanism_confidence: ESTABLISHED
  biological_scale: ORGANISM
  downstream:
  - target: Restrictive-Eating Psychopathology
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - metabo_psychiatric_liability
    description: >-
      Polygenic liability is placed upstream of the diagnostic psychopathology,
      but the intervening developmental, molecular, and neural mechanisms are
      unresolved.
    evidence:
    - reference: DOI:10.1038/s41398-023-02585-1
      reference_title: Genome-wide analysis of anorexia nervosa and major psychiatric disorders and related traits reveals genetic overlap and identifies novel risk loci for anorexia nervosa
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Our results indicate that some shared characteristics between AN and
        related disorders and traits may have genetic underpinnings.
      explanation: >-
        Genetic underpinnings support upstream susceptibility, while the
        authors do not establish a direct path to restrictive behavior.
  evidence:
  - reference: PMID:31308545
    reference_title: Genome-wide association study identifies eight risk loci and implicates metabo-psychiatric origins for anorexia nervosa.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These results further encourage a reconceptualization of anorexia nervosa
      as a metabo-psychiatric disorder.
    explanation: >-
      The landmark GWAS supports the metabo-psychiatric susceptibility framing.
- name: Restrictive-Eating Psychopathology
  description: >-
    Fear of weight gain, disturbance in body-weight or shape experience, and
    persistent weight-gain-interfering behavior motivate restriction. This
    clinical state is established; its upstream molecular and circuit causes
    remain incompletely resolved.
  biological_processes:
  - preferred_term: regulation of appetite
    term:
      id: GO:0032098
      label: regulation of appetite
    modifier: ABNORMAL
  - preferred_term: feeding behavior
    term:
      id: GO:0007631
      label: feeding behavior
    modifier: ABNORMAL
  mechanism_confidence: ESTABLISHED
  biological_scale: ORGANISM
  downstream:
  - target: Abnormal Eating Behavior
    causal_link_type: DIRECT
    description: >-
      Fear of weight gain, body-image disturbance, and persistent
      weight-gain-interfering behavior are expressed clinically as restrictive
      eating and related abnormal eating behavior.
    evidence:
    - reference: clinicaltrials:NCT03984344
      reference_title: A Feasibility Trial of Theta Burst Stimulation in Anorexia Nervosa (AN)
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Anorexia Nervosa (AN) is a life-threatening eating disorder
        characterised by an intense fear of weight gain and disturbed body
        image, which motivates severe dietary restriction or other weight loss
        behaviours (e.g. purging).
      explanation: >-
        The registry background directly connects the core psychopathology to
        restrictive and other abnormal eating behavior.
  - target: Sustained Energy Restriction
    causal_link_type: DIRECT
    description: >-
      AN psychopathology motivates severe dietary restriction and other
      weight-loss behavior.
    evidence:
    - reference: clinicaltrials:NCT03984344
      reference_title: A Feasibility Trial of Theta Burst Stimulation in Anorexia Nervosa (AN)
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Anorexia Nervosa (AN) is a life-threatening eating disorder
        characterised by an intense fear of weight gain and disturbed body
        image, which motivates severe dietary restriction or other weight loss
        behaviours (e.g. purging).
      explanation: >-
        The registry background directly describes the motivational link to
        restriction and weight-loss behavior.
  evidence:
  - reference: clinicaltrials:NCT03984344
    reference_title: A Feasibility Trial of Theta Burst Stimulation in Anorexia Nervosa (AN)
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Anorexia Nervosa (AN) is a life-threatening eating disorder characterised
      by an intense fear of weight gain and disturbed body image, which
      motivates severe dietary restriction or other weight loss behaviours
      (e.g. purging).
    explanation: >-
      The clinical-trial background summarizes the core psychopathology and
      restrictive behavior.
- name: Sustained Energy Restriction
  description: >-
    Persistent caloric restriction creates negative energy balance; in the
    binge-eating/purging presentation, vomiting or other compensatory behaviors
    can add fluid and electrolyte losses.
  biological_processes:
  - preferred_term: feeding behavior
    term:
      id: GO:0007631
      label: feeding behavior
    modifier: DECREASED
  mechanism_confidence: ESTABLISHED
  biological_scale: ORGANISM
  downstream:
  - target: Low Weight and Malnutrition
    causal_link_type: DIRECT
    description: >-
      Sustained energy restriction reduces body mass and produces chronic
      undernutrition.
    evidence:
    - reference: clinicaltrials:NCT03984344
      reference_title: A Feasibility Trial of Theta Burst Stimulation in Anorexia Nervosa (AN)
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Anorexia Nervosa (AN) is a life-threatening eating disorder
        characterised by an intense fear of weight gain and disturbed body
        image, which motivates severe dietary restriction or other weight loss
        behaviours (e.g. purging).
      explanation: >-
        The description directly links severe restriction with weight-loss
        behavior.
  - target: Electrolyte and Volume Disturbance
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Purging, polydipsia, reduced intake, and renal adaptation
    description: >-
      Electrolyte and volume abnormalities are context dependent and are not
      universal; purging and water-loading behaviors can substantially modify
      risk.
    evidence:
    - reference: PMID:16721178
      reference_title: Medical complications of anorexia nervosa and bulimia nervosa.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Nutritional abnormalities are also common, including sodium depletion
        and hypovolemia, hypophosphatemia and hypomagnesemia.
      explanation: >-
        The medical-complications review supports electrolyte and volume
        abnormalities while the edge records known behavioral intermediates.
  evidence:
  - reference: clinicaltrials:NCT03984344
    reference_title: A Feasibility Trial of Theta Burst Stimulation in Anorexia Nervosa (AN)
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Anorexia Nervosa (AN) is a life-threatening eating disorder characterised
      by an intense fear of weight gain and disturbed body image, which
      motivates severe dietary restriction or other weight loss behaviours
      (e.g. purging).
    explanation: >-
      The source directly supports restriction and other weight-loss behavior
      as defining AN events.
- name: Low Weight and Malnutrition
  description: >-
    The low-energy state is the established proximal driver of many endocrine,
    cardiovascular, gastrointestinal, skeletal, and brain-state consequences.
    It should not be mistaken for evidence that those downstream changes caused
    the initial psychiatric syndrome.
  mechanism_confidence: ESTABLISHED
  biological_scale: ORGANISM
  downstream:
  - target: Low Body Weight and Weight Loss
    causal_link_type: DIRECT
    description: >-
      The malnourished low-energy state is expressed clinically as decreased
      body weight, often following substantial or rapid weight loss.
    evidence:
    - reference: PMID:34418241
      reference_title: "Determinants of severe bradycardia in adolescents hospitalized for anorexia nervosa."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Patients in this group had a higher maximum lifetime weight (P =
        0.0045), greater premorbid weight loss (P = 0.0011), and more rapid
        weight loss (P = 0.0001).
      explanation: >-
        Hospitalized adolescent data document the substantial and rapid weight
        loss that produces the low-weight clinical state.
  - target: Hypoleptinemia
    causal_link_type: DIRECT
    description: >-
      Loss of adipose tissue and reduced energy intake lower the
      adipocyte-derived hormone leptin, producing the hypoleptinemia that
      signals the starved state.
    evidence:
    - reference: PMID:31156489
      reference_title: "Clinical Trials Required to Assess Potential Benefits and Side Effects of Treatment of Patients With Anorexia Nervosa With Recombinant Human Leptin."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        Patients with AN present hypoleptinemia in accordance with both their
        reduced energy intake and fat mass
      explanation: >-
        The review states that hypoleptinemia in AN tracks reduced energy intake
        and fat mass, supporting the low-weight state as the direct cause of
        hypoleptinemia.
  - target: Starvation-Adaptation Endocrine Response
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Hypothalamic-pituitary axis adaptation to chronic energy deficit
    description: >-
      Chronic starvation elicits adaptive and maladaptive changes across
      gonadal, growth-hormone, adrenal, thyroid, and appetite-hormone axes.
    evidence:
    - reference: PMID:27811940
      reference_title: "The endocrine manifestations of anorexia nervosa: mechanisms and management."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Although most, but not all, of these endocrine disturbances are
        adaptive to the low energy state of chronic starvation and reverse with
        treatment of the eating disorder, many contribute to impaired skeletal
        integrity, as well as neuropsychiatric comorbidities, in individuals
        with anorexia nervosa.
      explanation: >-
        The review explicitly identifies chronic low energy as the driver of
        most endocrine disturbances.
  - target: Cardiovascular Adaptation and Instability
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Autonomic adaptation, reduced cardiac mass, and electrolyte disturbance
    description: >-
      Recent and rapid weight loss contributes to bradycardia and broader
      cardiovascular instability.
    evidence:
    - reference: PMID:34418241
      reference_title: "Determinants of severe bradycardia in adolescents hospitalized for anorexia nervosa."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        This study confirms that recent weight loss is probably the most
        important determinant of severe bradycardia in adolescents with AN.
      explanation: >-
        Hospitalized adolescent data directly associate recent weight loss with
        severe bradycardia.
  - target: Gastrointestinal Dysmotility
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Malnutrition-associated autonomic and motility changes
    description: >-
      Disordered eating and malnutrition produce delayed gastric emptying and
      constipation that can complicate refeeding.
    evidence:
    - reference: PMID:16962383
      reference_title: "Gastrointestinal disturbances in eating disorders: clinical and neurobiological aspects."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Gastrointestinal disturbances develop secondary to the disordered
        eating behaviour and the concomitant malnutrition and subside mostly
        with the resumption of normal food intake and body weight.
      explanation: >-
        The review explicitly identifies malnutrition as upstream of the GI
        disturbances.
  - target: Undernutrition-Associated Brain Structural Changes
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Acute undernutrition and lower body mass index
    hypothesis_groups:
    - neural_state_trait_model
    description: >-
      A substantial component of widespread brain structural differences is
      associated with acute undernutrition and is smaller after partial weight
      restoration.
    evidence:
    - reference: PMID:36031441
      reference_title: "Brain Structure in Acutely Underweight and Partially Weight-Restored Individuals With Anorexia Nervosa: A Coordinated Analysis by the ENIGMA Eating Disorders Working Group."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Highlighting the effects of undernutrition, these deficits were associated
        with lower body mass index in the AN sample and were less pronounced in
        partially weight-restored patients.
      explanation: >-
        The multicenter analysis supports a starvation-state contribution to
        brain structural differences.
  evidence:
  - reference: PMID:27811940
    reference_title: "The endocrine manifestations of anorexia nervosa: mechanisms and management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Anorexia nervosa is a psychiatric disorder characterized by altered body
      image, persistent food restriction and low body weight, and is associated
      with global endocrine dysregulation in both adolescent girls and women.
    explanation: >-
      The review supports low weight as the clinical state associated with
      systemic endocrine consequences.
- name: Starvation-Adaptation Endocrine Response
  description: >-
    Chronic low energy alters hypothalamic-pituitary-gonadal, growth-hormone,
    adrenal, thyroid, leptin, ghrelin, and related endocrine axes. Many changes
    are adaptive to starvation, not validated diagnostic biomarkers.
  biological_processes:
  - preferred_term: response to starvation
    term:
      id: GO:0042594
      label: response to starvation
    modifier: ABNORMAL
  - preferred_term: energy homeostasis
    term:
      id: GO:0097009
      label: energy homeostasis
    modifier: ABNORMAL
  - preferred_term: hormone-mediated signaling pathway
    term:
      id: GO:0009755
      label: hormone-mediated signaling pathway
    modifier: ABNORMAL
  cell_types:
  - preferred_term: endocrine cell
    term:
      id: CL:0000163
      label: endocrine cell
  mechanism_confidence: ESTABLISHED
  biological_scale: ORGANISM
  downstream:
  - target: Hypogonadotropic Hypogonadism
    causal_link_type: DIRECT
    description: >-
      Hypothalamic-pituitary dysfunction suppresses gonadal hormone signaling.
    evidence:
    - reference: PMID:27811940
      reference_title: "The endocrine manifestations of anorexia nervosa: mechanisms and management."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Dysfunction of the hypothalamic-pituitary axis includes hypogonadotropic
        hypogonadism with relative oestrogen and androgen deficiency, growth
        hormone resistance, hypercortisolaemia, non-thyroidal illness syndrome,
        hyponatraemia and hypooxytocinaemia.
      explanation: >-
        The endocrine review directly identifies hypogonadotropic hypogonadism.
  - target: Skeletal Integrity Loss
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Low gonadal steroids, growth-hormone resistance, hypercortisolemia, and low body mass
    description: >-
      Starvation-related endocrine changes and altered body composition impair
      bone accrual and maintenance.
    evidence:
    - reference: PMID:27811940
      reference_title: "The endocrine manifestations of anorexia nervosa: mechanisms and management."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Although most, but not all, of these endocrine disturbances are
        adaptive to the low energy state of chronic starvation and reverse with
        treatment of the eating disorder, many contribute to impaired skeletal
        integrity, as well as neuropsychiatric comorbidities, in individuals
        with anorexia nervosa.
      explanation: >-
        The review directly states that endocrine disturbances contribute to
        impaired skeletal integrity.
  evidence:
  - reference: DOI:10.3390/nu16132095
    reference_title: "Peripheral Biomarkers of Anorexia Nervosa: A Meta-Analysis"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Our findings indicate that peripheral biomarkers may be linked to the
      pathophysiology of AN, such as processes of adaptation to starvation.
    explanation: >-
      Meta-analysis supports a broad starvation-adaptation biomarker pattern
      while appropriately using associative language.
- name: Hypogonadotropic Hypogonadism
  description: >-
    Energy-deficit-associated hypothalamic-pituitary suppression reduces
    gonadal hormones. Amenorrhea is an important manifestation in some
    postmenarchal patients but is not required for a modern AN diagnosis.
  locations:
  - preferred_term: hypothalamus
    term:
      id: UBERON:0001898
      label: hypothalamus
  mechanism_confidence: ESTABLISHED
  biological_scale: ORGANISM
  downstream:
  - target: Amenorrhea
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Reduced hypothalamic-pituitary-gonadal signaling and low gonadal steroids
    description: >-
      Suppression of reproductive endocrine signaling can result in
      hypothalamic amenorrhea.
    evidence:
    - reference: PMID:36401318
      reference_title: "Associations between bone mineral density, body composition and amenorrhoea in females with eating disorders: a systematic review and meta-analysis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        In AN, low weight, hypothalamic amenorrhoea, and longer illness duration
        are established risk factors for low BMD
      explanation: >-
        The systematic review explicitly identifies hypothalamic amenorrhea in
        AN and its bone-health context.
  evidence:
  - reference: PMID:27811940
    reference_title: "The endocrine manifestations of anorexia nervosa: mechanisms and management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Dysfunction of the hypothalamic-pituitary axis includes hypogonadotropic
      hypogonadism with relative oestrogen and androgen deficiency
    explanation: >-
      The review directly supports the reproductive-axis mechanism.
- name: Skeletal Integrity Loss
  description: >-
    Low body mass, low fat and lean mass, amenorrhea, and endocrine adaptation
    reduce bone mineral density and increase later osteoporosis and fracture
    risk.
  locations:
  - preferred_term: bone tissue
    term:
      id: UBERON:0002481
      label: bone tissue
  mechanism_confidence: ESTABLISHED
  biological_scale: TISSUE
  downstream:
  - target: Reduced Bone Mineral Density
    causal_link_type: DIRECT
    description: >-
      Impaired bone integrity is measured clinically as reduced bone mineral
      density across total body, spine, hip, and femur sites.
    evidence:
    - reference: PMID:36401318
      reference_title: "Associations between bone mineral density, body composition and amenorrhoea in females with eating disorders: a systematic review and meta-analysis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        BMD in individuals with AN (total body, spine, hip, and femur), with BN
        (total body and spine) and with OSFED (spine) was lower than in HC.
      explanation: >-
        The meta-analysis directly supports reduced BMD at multiple sites in
        AN.
  evidence:
  - reference: PMID:36401318
    reference_title: "Associations between bone mineral density, body composition and amenorrhoea in females with eating disorders: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Lower bone mineral density (BMD) increases the risk of osteoporosis in
      individuals with eating disorders (EDs), particularly women with
      anorexia nervosa (AN), making them susceptible to pain and fractures
      throughout adulthood.
    explanation: >-
      The review describes the clinically important skeletal consequence and
      its population context.
- name: Cardiovascular Adaptation and Instability
  description: >-
    Weight loss, autonomic adaptation, reduced cardiac mass, and electrolyte
    disturbances contribute to bradycardia, conduction disturbance, and
    arrhythmia risk. Not every patient has the same cardiovascular phenotype.
  locations:
  - preferred_term: cardiovascular system
    term:
      id: UBERON:0004535
      label: cardiovascular system
  mechanism_confidence: ESTABLISHED
  biological_scale: TISSUE
  downstream:
  - target: Bradycardia
    causal_link_type: DIRECT
    description: >-
      Recent and rapid weight loss is strongly associated with severe
      bradycardia in hospitalized adolescents.
    evidence:
    - reference: PMID:34418241
      reference_title: "Determinants of severe bradycardia in adolescents hospitalized for anorexia nervosa."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Multivariate analysis showed that recent weight loss is an independent
        predictor of bradycardia at hospital admission (R2 : 0.35, P = 0.0001).
      explanation: >-
        The cohort supports weight-loss-associated bradycardia in the
        hospitalized adolescent population.
  - target: Arrhythmia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Myocardial structural change, conduction disturbance, and electrolyte imbalance
    description: >-
      AN can confer arrhythmia risk through several cardiac and electrolyte
      pathways.
    evidence:
    - reference: PMID:16721178
      reference_title: Medical complications of anorexia nervosa and bulimia nervosa.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Acrocyanosis is common, and patients with anorexia nervosa are at risk
        of various arrhythmias.
      explanation: >-
        The medical-complications review explicitly identifies arrhythmia risk
        in AN.
  evidence:
  - reference: DOI:10.1001/jamanetworkopen.2024.51094
    reference_title: Incidence and Risk of Cardiovascular Outcomes in Patients With Anorexia Nervosa
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Compared with the control group, the AN group had significantly higher
      risks of MACE (adjusted HR [AHR], 3.78; 95% CI, 2.83-5.05) and any
      cardiovascular condition (AHR, 1.93; 95% CI, 1.54-2.41).
    explanation: >-
      A national matched cohort quantifies increased cardiovascular risk but
      does not imply that every cardiovascular outcome is a starvation-only
      effect.
- name: Electrolyte and Volume Disturbance
  description: >-
    Restriction, purging, polydipsia, and renal adaptation can produce
    electrolyte and volume abnormalities. These are severity- and
    behavior-dependent complications rather than universal diagnostic signs.
  mechanism_confidence: ESTABLISHED
  biological_scale: ORGANISM
  downstream:
  - target: Hypokalemia
    causal_link_type: DIRECT
    description: >-
      Potassium depletion can occur, particularly with purging behaviors.
    evidence:
    - reference: PMID:40048192
      reference_title: "Eating Disorders: A Review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        These disorders may be associated with changes in weight, electrolyte
        abnormalities (eg, hyponatremia, hypokalemia), bradycardia,
        disturbances in reproductive hormones (eg, decreased estradiol levels
        in females), and decreased bone density.
      explanation: >-
        The clinical review explicitly names hypokalemia among medical
        complications of eating disorders, including AN.
  - target: Hyponatremia
    causal_link_type: DIRECT
    description: >-
      Sodium disturbance can occur through reduced intake, volume regulation,
      or excessive water intake.
    evidence:
    - reference: PMID:40048192
      reference_title: "Eating Disorders: A Review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        These disorders may be associated with changes in weight, electrolyte
        abnormalities (eg, hyponatremia, hypokalemia), bradycardia,
        disturbances in reproductive hormones (eg, decreased estradiol levels
        in females), and decreased bone density.
      explanation: >-
        The review explicitly names hyponatremia among medical complications.
  - target: Arrhythmia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Electrolyte-sensitive cardiac conduction disturbance
    description: >-
      Electrolyte imbalance can amplify arrhythmia risk, especially in
      medically unstable or purging presentations.
    evidence:
    - reference: PMID:16721178
      reference_title: Medical complications of anorexia nervosa and bulimia nervosa.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Acrocyanosis is common, and patients with anorexia nervosa are at risk
        of various arrhythmias. Low-weight patients are at high risk for
        osteopenia/osteoporosis. Nutritional abnormalities are also common,
        including sodium depletion and hypovolemia, hypophosphatemia and
        hypomagnesemia.
      explanation: >-
        The review documents both arrhythmias and electrolyte/volume
        abnormalities but does not isolate a single electrolyte-to-arrhythmia
        causal effect; the edge is therefore partial and indirect.
  evidence:
  - reference: PMID:16721178
    reference_title: Medical complications of anorexia nervosa and bulimia nervosa.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Nutritional abnormalities are also common, including sodium depletion and
      hypovolemia, hypophosphatemia and hypomagnesemia.
    explanation: >-
      The review supports clinically important electrolyte and volume
      abnormalities in low-weight eating-disorder populations.
- name: Gastrointestinal Dysmotility
  description: >-
    Delayed gastric emptying and constipation occur in both AN presentations
    and can make nutritional rehabilitation uncomfortable; most changes improve
    with restoration of normal intake and body weight.
  locations:
  - preferred_term: gastrointestinal tract
    term:
      id: UBERON:0005409
      label: alimentary part of gastrointestinal system
  mechanism_confidence: ESTABLISHED
  biological_scale: TISSUE
  downstream:
  - target: Constipation
    causal_link_type: DIRECT
    description: >-
      Gastrointestinal dysmotility manifests clinically as constipation.
    evidence:
    - reference: PMID:16962383
      reference_title: "Gastrointestinal disturbances in eating disorders: clinical and neurobiological aspects."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Both anorexia nervosa subtypes experience substantial delays in gastric
        emptying as well as constipation.
      explanation: >-
        The review directly supports constipation across both AN
        presentations.
  evidence:
  - reference: PMID:16962383
    reference_title: "Gastrointestinal disturbances in eating disorders: clinical and neurobiological aspects."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Gastrointestinal disturbances develop secondary to the disordered eating
      behaviour and the concomitant malnutrition and subside mostly with the
      resumption of normal food intake and body weight.
    explanation: >-
      The review supports both the secondary mechanism and reversibility with
      nutritional recovery.
- name: Undernutrition-Associated Brain Structural Changes
  description: >-
    Acute AN is associated with widespread reductions in cortical thickness
    and subcortical volume. Their relationship to low BMI and attenuation after
    partial weight restoration make them important state markers but not proof
    of a primary neural cause.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  locations:
  - preferred_term: brain
    term:
      id: UBERON:0000955
      label: brain
  mechanism_confidence: ESTABLISHED
  biological_scale: TISSUE
  evidence:
  - reference: PMID:36031441
    reference_title: "Brain Structure in Acutely Underweight and Partially Weight-Restored Individuals With Anorexia Nervosa: A Coordinated Analysis by the ENIGMA Eating Disorders Working Group."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In AN, reductions in cortical thickness, subcortical volumes, and, to a
      lesser extent, cortical surface area were sizable (Cohen's d up to 0.95),
      widespread, and colocalized with hub regions.
    explanation: >-
      The multicenter analysis establishes the structural imaging state while
      the node description preserves causal uncertainty.
- name: Immune and Microbiome Correlates
  description: >-
    Cytokine and microbiome changes have been measured longitudinally in
    adolescents with AN. They remain correlates: this node has no causal
    downstream edge to depression, weight loss, or other phenotypes.
  biological_processes:
  - preferred_term: cytokine-mediated signaling pathway
    term:
      id: GO:0019221
      label: cytokine-mediated signaling pathway
    modifier: ABNORMAL
  cell_types:
  - preferred_term: lymphocyte
    term:
      id: CL:0000542
      label: lymphocyte
  mechanism_confidence: PROVISIONAL
  biological_scale: ORGANISM
  evidence:
  - reference: DOI:10.3390/nu16111596
    reference_title: Cytokine and Microbiome Changes in Adolescents with Anorexia Nervosa at Admission, Discharge, and One-Year Follow-Up
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Relative to the HC group, serum levels of IL-1β and IL-6 were
      significantly lower during the acute phase (admission) of AN.
    explanation: >-
      Longitudinal adolescent case-control data support an acute-phase cytokine
      association without resolving causal direction.
- name: Hypoleptinemia
  description: >-
    Low circulating leptin — the state — arising from loss of adipose
    (leptin-secreting) tissue during energy restriction. Hypoleptinemia is a
    core endocrine feature of the acute starved state, is the afferent signal
    for adaptation to starvation, and is the mechanistic target of
    recombinant-leptin (metreleptin) substitution. It arises from the
    upstream low-weight/malnutrition state modeled elsewhere in this graph.
  mechanism_confidence: ESTABLISHED
  biological_scale: ORGANISM
  biological_processes:
  - preferred_term: Leptin-mediated signaling pathway
    term:
      id: GO:0033210
      label: leptin-mediated signaling pathway
    modifier: DECREASED
  cell_types:
  - preferred_term: Adipocyte (leptin-secreting)
    term:
      id: CL:0000136
      label: adipocyte
  downstream:
  - target: Hypogonadotropic Hypogonadism
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Loss of leptin's permissive signal for hypothalamic GnRH / HPG-axis activity
    description: >-
      Hypoleptinemia removes a permissive signal for the reproductive axis,
      contributing to hypothalamic hypogonadism and amenorrhea; this is the
      leptin-specific mediator of the broader endocrine starvation response.
    evidence:
    - reference: PMID:31156489
      reference_title: "Clinical Trials Required to Assess Potential Benefits and Side Effects of Treatment of Patients With Anorexia Nervosa With Recombinant Human Leptin."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        Hypoleptinemia acts as a key trigger for the adaptation to starvation by
        affecting diverse brain regions including the reward system
      explanation: >-
        The review identifies hypoleptinemia as the trigger of the
        neuroendocrine adaptations to starvation, including reproductive-axis
        suppression.
  - target: Excessive Physical Activity
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Leptin signal transduction via STAT3 in ventral tegmental area (VTA) dopaminergic neurons (demonstrated in the activity-based anorexia model)
    hypothesis_groups:
    - leptin_hyperactivity
    description: >-
      Low leptin is hypothesized to drive starvation-induced hyperactivity; the
      causal step is established in the ABA rodent model (via VTA STAT3
      signaling) but only correlational (inverted-U) in humans, so this edge is
      carried under an emerging hypothesis rather than as an established human
      mechanism.
    evidence:
    - reference: PMID:31156489
      reference_title: "Clinical Trials Required to Assess Potential Benefits and Side Effects of Treatment of Patients With Anorexia Nervosa With Recombinant Human Leptin."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        an inverted U-shaped relationship has been observed between their serum
        leptin levels and physical activity.
      explanation: >-
        Human data are correlational (inverted-U), supporting association but
        not establishing the causal direction, hence the emerging-hypothesis
        grouping.
    - reference: PMID:31156489
      reference_title: "Clinical Trials Required to Assess Potential Benefits and Side Effects of Treatment of Patients With Anorexia Nervosa With Recombinant Human Leptin."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        STAT3 signaling in dopaminergic neurons in the ventral tegmental area
        (VTA) plays a crucial role in the transmission of the leptin signal in
        ABA.
      explanation: >-
        The ABA rodent model identifies VTA STAT3 signaling as the intermediate
        transducing the leptin signal to activity, supporting known
        intermediates for this (model-derived) edge.
  evidence:
  - reference: PMID:38303556
    reference_title: "Does hypoleptinemia trigger entrapment in anorexia nervosa? Etiological and clinical considerations."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Hypoleptinemia as a core endocrine feature of AN serves as a central and
      peripheral trigger of tissue-specific adaptations to starvation.
    explanation: >-
      Narrative review (no primary human data) establishes hypoleptinemia as the
      core endocrine trigger of starvation adaptation in anorexia nervosa.
phenotypes:
- name: Abnormal Eating Behavior
  category: Behavioral
  diagnostic: true
  description: >-
    Persistent restriction and other behavior that interferes with weight gain
    are core diagnostic manifestations. Fear of weight gain and body-image
    disturbance are retained in the clinical description because the available
    HPO term is broader than the full psychiatric construct.
  phenotype_term:
    preferred_term: Restrictive eating and weight-gain-interfering behavior
    term:
      id: HP:0100738
      label: Abnormal eating behavior
  evidence:
  - reference: clinicaltrials:NCT03984344
    reference_title: A Feasibility Trial of Theta Burst Stimulation in Anorexia Nervosa (AN)
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Anorexia Nervosa (AN) is a life-threatening eating disorder characterised
      by an intense fear of weight gain and disturbed body image, which
      motivates severe dietary restriction or other weight loss behaviours
      (e.g. purging).
    explanation: >-
      The source directly describes the diagnostic psychopathology and
      restrictive behavior.
- name: Low Body Weight and Weight Loss
  category: Growth
  diagnostic: true
  description: >-
    Significantly low body weight is a defining state. Recent weight loss can
    carry medical risk even before an extremely low absolute weight is reached.
  phenotype_term:
    preferred_term: Significantly low body weight and weight loss
    term:
      id: HP:0004325
      label: Decreased body weight
  evidence:
  - reference: PMID:34418241
    reference_title: "Determinants of severe bradycardia in adolescents hospitalized for anorexia nervosa."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Patients in this group had a higher maximum lifetime weight (P = 0.0045),
      greater premorbid weight loss (P = 0.0011), and more rapid weight loss (P
      = 0.0001).
    explanation: >-
      Hospitalized adolescent data document clinically consequential recent
      weight loss in AN.
- name: Bradycardia
  category: Cardiovascular
  description: >-
    Bradycardia is common in medically unstable, recently weight-losing
    adolescents and may prompt hospitalization; the cohort estimate below is
    specific to hospitalized adolescents and is not a population frequency.
  phenotype_term:
    preferred_term: Bradycardia
    term:
      id: HP:0001662
      label: Bradycardia
  evidence:
  - reference: PMID:34418241
    reference_title: "Determinants of severe bradycardia in adolescents hospitalized for anorexia nervosa."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Forty-eight percent of the AN patient admissions were due to severe
      bradycardia (AN-B+ group).
    explanation: >-
      The estimate is explicitly confined to a hospitalized adolescent cohort;
      no KB-wide frequency band is inferred.
- name: Arrhythmia
  category: Cardiovascular
  description: >-
    Arrhythmias are potentially serious complications of AN, mediated through
    cardiac structural, conduction, autonomic, and electrolyte pathways.
  phenotype_term:
    preferred_term: Arrhythmia
    term:
      id: HP:0011675
      label: Arrhythmia
  evidence:
  - reference: PMID:16721178
    reference_title: Medical complications of anorexia nervosa and bulimia nervosa.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Acrocyanosis is common, and patients with anorexia nervosa are at risk of
      various arrhythmias.
    explanation: >-
      The medical-complications review directly identifies arrhythmia risk.
- name: Amenorrhea
  category: Genitourinary
  description: >-
    Hypothalamic amenorrhea can occur in postmenarchal patients with AN. It is a
    consequence of energy-deficit-associated reproductive-axis suppression and
    is not required for diagnosis; it does not apply to all sexes or life
    stages.
  phenotype_term:
    preferred_term: Hypothalamic amenorrhea in postmenarchal patients
    term:
      id: HP:0000141
      label: Amenorrhea
  evidence:
  - reference: PMID:36401318
    reference_title: "Associations between bone mineral density, body composition and amenorrhoea in females with eating disorders: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In AN, low weight, hypothalamic amenorrhoea, and longer illness duration
      are established risk factors for low BMD
    explanation: >-
      The systematic review explicitly identifies hypothalamic amenorrhea in
      females with AN.
- name: Reduced Bone Mineral Density
  category: Skeletal
  description: >-
    Reduced bone mineral density is a major long-term complication, especially
    in women with low body mass, altered body composition, and amenorrhea; the
    evidence base cited here is predominantly female.
  phenotype_term:
    preferred_term: Reduced bone mineral density
    term:
      id: HP:0004349
      label: Reduced bone mineral density
  evidence:
  - reference: PMID:36401318
    reference_title: "Associations between bone mineral density, body composition and amenorrhoea in females with eating disorders: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      BMD in individuals with AN (total body, spine, hip, and femur), with BN
      (total body and spine) and with OSFED (spine) was lower than in HC.
    explanation: >-
      Meta-analysis of female cohorts confirms lower BMD across multiple sites
      in AN.
- name: Hypokalemia
  category: Metabolism
  description: >-
    Hypokalemia can occur, particularly with purging or other fluid-loss
    behaviors, but is not universal across AN presentations.
  phenotype_term:
    preferred_term: Hypokalemia
    term:
      id: HP:0002900
      label: Hypokalemia
  context: Increased concern with purging behavior or medical instability
  evidence:
  - reference: PMID:40048192
    reference_title: "Eating Disorders: A Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These disorders may be associated with changes in weight, electrolyte
      abnormalities (eg, hyponatremia, hypokalemia), bradycardia,
      disturbances in reproductive hormones (eg, decreased estradiol levels
      in females), and decreased bone density.
    explanation: >-
      The review includes AN among eating disorders with hypokalemia while the
      phenotype context avoids implying universality.
- name: Hyponatremia
  category: Metabolism
  description: >-
    Hyponatremia can occur through water-loading behavior, reduced intake, or
    altered volume regulation and requires context-specific interpretation.
  phenotype_term:
    preferred_term: Hyponatremia
    term:
      id: HP:0002902
      label: Hyponatremia
  context: Medical instability, altered fluid intake, or volume dysregulation
  evidence:
  - reference: PMID:27811940
    reference_title: "The endocrine manifestations of anorexia nervosa: mechanisms and management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Dysfunction of the hypothalamic-pituitary axis includes hypogonadotropic
      hypogonadism with relative oestrogen and androgen deficiency, growth
      hormone resistance, hypercortisolaemia, non-thyroidal illness syndrome,
      hyponatraemia and hypooxytocinaemia.
    explanation: >-
      The endocrine review explicitly includes hyponatremia among AN-associated
      disturbances.
- name: Constipation
  category: Digestive
  description: >-
    Constipation and delayed gastric emptying occur in both AN presentations,
    often improve with nutritional recovery, and may complicate refeeding.
  phenotype_term:
    preferred_term: Constipation
    term:
      id: HP:0002019
      label: Constipation
  evidence:
  - reference: PMID:16962383
    reference_title: "Gastrointestinal disturbances in eating disorders: clinical and neurobiological aspects."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Both anorexia nervosa subtypes experience substantial delays in gastric
      emptying as well as constipation.
    explanation: >-
      The review directly supports constipation in both AN presentations.
- name: Anxiety
  category: Behavioral
  description: >-
    Anxiety disorders are frequent psychiatric comorbidities. They are not
    represented as a downstream consequence of cytokine or microbiome findings.
  phenotype_term:
    preferred_term: Anxiety
    term:
      id: HP:0000739
      label: Anxiety
  evidence:
  - reference: DOI:10.1007/s00115-025-01820-y
    reference_title: Anorexia nervosa—an update
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It is frequently associated with other psychiatric disorders, such as
      depression, anxiety and obsessive-compulsive disorders as well as
      numerous physical complications.
    explanation: >-
      The clinical update identifies anxiety as a frequent comorbidity.
- name: Depression
  category: Behavioral
  description: >-
    Depression is a frequent and clinically important psychiatric comorbidity;
    cross-sectional association does not establish directionality.
  phenotype_term:
    preferred_term: Depression
    term:
      id: HP:0000716
      label: Depression
  evidence:
  - reference: PMID:40048192
    reference_title: "Eating Disorders: A Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Individuals with anorexia nervosa, bulimia nervosa, and binge-eating
      disorder have high lifetime rates of depression (76.3% for bulimia
      nervosa, 65.5% for binge-eating disorder, and 49.5% for anorexia nervosa)
      and higher rates of suicide attempts than those without eating disorders.
    explanation: >-
      The review provides an AN-specific lifetime depression estimate.
- name: Obsessive-Compulsive Trait
  category: Behavioral
  description: >-
    Obsessive-compulsive traits or disorder may co-occur with AN. Food rituals
    and cognitive rigidity should not automatically be equated with a separate
    obsessive-compulsive disorder diagnosis.
  phenotype_term:
    preferred_term: Obsessive-compulsive trait
    term:
      id: HP:0008770
      label: Obsessive-compulsive trait
  evidence:
  - reference: DOI:10.1007/s00115-025-01820-y
    reference_title: Anorexia nervosa—an update
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It is frequently associated with other psychiatric disorders, such as
      depression, anxiety and obsessive-compulsive disorders as well as
      numerous physical complications.
    explanation: >-
      The update supports obsessive-compulsive comorbidity but does not
      quantify the broader trait in all patients, so support is partial.
- name: Excessive Physical Activity
  category: Behavioral
  description: >-
    Physical hyperactivity, motor restlessness, and a driven urge to exercise
    are common in acute AN and correlate inversely with serum leptin; they are
    modeled here as a leptin-linked behavioral manifestation (see the
    leptin_hyperactivity mechanistic hypothesis). HP:0000752 (Hyperactivity) is
    the closest available HPO term but is anchored to ADHD-type motor/attentional
    hyperactivity; the preferred_term carries the AN-specific compulsive,
    starvation-driven-exercise nuance the ontology class does not yet capture.
  phenotype_term:
    preferred_term: Excessive physical activity / motor restlessness
    term:
      id: HP:0000752
      label: Hyperactivity
  evidence:
  - reference: PMID:31156489
    reference_title: "Clinical Trials Required to Assess Potential Benefits and Side Effects of Treatment of Patients With Anorexia Nervosa With Recombinant Human Leptin."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      an inverted U-shaped relationship has been observed between their serum
      leptin levels and physical activity.
    explanation: >-
      Human data document an inverted-U association between serum leptin and
      physical activity in AN, supporting hyperactivity as a leptin-linked
      manifestation.
biochemical:
- name: Hypoleptinemia
  biomarker_term:
    preferred_term: Leptin
    term:
      id: NCIT:C46081
      label: Leptin
  notes: >-
    Markedly low circulating leptin is an endocrinological hallmark of the acute
    underweight state of AN, resulting from the loss of adipose (leptin-secreting)
    tissue during energy restriction. Leptin partially normalizes with weight
    restoration. Hypoleptinemia is not diagnostic of AN in isolation (it reflects
    low fat mass from any cause) but is the biomarker that indexes the
    starvation-adaptation state and the target of metreleptin substitution.
  specificity: >-
    Low for AN as a stand-alone diagnostic marker (reflects low fat mass
    generally); high as an index of the acute starvation-adaptation state.
  presence: DECREASED
  cell_types:
  - preferred_term: Adipocyte (leptin-secreting)
    term:
      id: CL:0000136
      label: adipocyte
  readouts:
  - target: Hypoleptinemia
    relationship: READOUT_OF
    direction: NEGATIVE
    endpoint_context: MONITORING
    interpretation: >-
      Low serum leptin is a direct readout of the Hypoleptinemia mechanism node
      and indexes the severity of the starvation-adaptation state; it partially
      normalizes with weight restoration and is the pharmacodynamic target of
      metreleptin substitution.
  evidence:
  - reference: PMID:31156489
    reference_title: "Clinical Trials Required to Assess Potential Benefits and Side Effects of Treatment of Patients With Anorexia Nervosa With Recombinant Human Leptin."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Hypoleptinemia acts as a key trigger for the adaptation to starvation by
      affecting diverse brain regions including the reward system
    explanation: >-
      The review identifies hypoleptinemia as the central endocrine feature and
      trigger of starvation adaptation in AN.
  - reference: PMID:38303556
    reference_title: "Does hypoleptinemia trigger entrapment in anorexia nervosa? Etiological and clinical considerations."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Hypoleptinemia as a core endocrine feature of AN serves as a central and
      peripheral trigger of tissue-specific adaptations to starvation.
    explanation: >-
      Narrative review (no primary human data) confirms hypoleptinemia as a
      core, characteristic endocrine feature of anorexia nervosa.
- name: Elevated Soluble Leptin Receptor
  biomarker_term:
    preferred_term: Leptin Receptor
    term:
      id: NCIT:C26349
      label: Leptin Receptor
  notes: >-
    Soluble leptin receptor (sOB-R, the shed/cleaved extracellular domain of the
    leptin receptor) circulates at elevated levels in acute anorexia nervosa.
    sOB-R acts as a circulating leptin antagonist by sequestering leptin and
    reducing its bioavailability; together with hypoleptinemia (low total leptin),
    sOB-R elevation reflects a dual-arm dysfunction in the leptin signaling system
    during starvation adaptation. The elevation of sOB-R complements the findings
    of low total leptin and indexes the severity of leptin resistance in the
    starvation state.
  specificity: >-
    Low as a stand-alone diagnostic marker (elevated sOB-R can occur in other
    states of metabolic stress and altered leptin signaling); high as part of the
    dual biomarker pattern (hypoleptinemia + sOB-R elevation) characterizing the
    acute AN starvation state.
  presence: INCREASED
  evidence:
  - reference: DOI:10.3390/nu16132095
    reference_title: "Peripheral Biomarkers of Anorexia Nervosa: A Meta-Analysis"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      soluble leptin receptor levels were significantly higher in cases of AN
      compared with those in non-AN controls
    explanation: >-
      Wu et al. 2024 meta-analysis of 52 peripheral biomarkers identifies sOB-R
      elevation as a robust finding across multiple AN cohorts.
diagnosis:
- name: Clinical eating-disorder assessment
  presence: >-
    Diagnosis is clinical: persistent energy restriction and significantly low
    body weight are evaluated together with fear of weight gain or persistent
    weight-gain-interfering behavior and disturbance in body-weight or shape
    experience. Motivation and developmental context matter, and no peripheral
    biomarker establishes the diagnosis.
  diagnosis_term:
    preferred_term: clinical assessment
    term:
      id: NCIT:C124351
      label: Clinical Evaluation
  evidence:
  - reference: DOI:10.1038/s41398-023-02585-1
    reference_title: Genome-wide analysis of anorexia nervosa and major psychiatric disorders and related traits reveals genetic overlap and identifies novel risk loci for anorexia nervosa
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Anorexia nervosa (AN) is an eating disorder characterized by restricted
      energy intake, abnormally low body weight, intense fear of weight-gain,
      and body image disturbances [ 1].
    explanation: >-
      The source succinctly states the core clinical phenotype used for
      diagnostic assessment.
- name: Nutritional, electrolyte, and endocrine assessment
  presence: >-
    Weight trajectory, intake, hydration, electrolytes, renal and hepatic
    function, blood counts, and endocrine complications are assessed according
    to illness severity and behavior context. Normal absolute weight does not
    exclude risk from rapid recent loss.
  diagnosis_term:
    preferred_term: nutrition assessment
    term:
      id: NCIT:C124351
      label: Clinical Evaluation
  evidence:
  - reference: PMID:40048192
    reference_title: "Eating Disorders: A Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These disorders may be associated with changes in weight, electrolyte
      abnormalities (eg, hyponatremia, hypokalemia), bradycardia,
      disturbances in reproductive hormones (eg, decreased estradiol levels
      in females), and decreased bone density.
    explanation: >-
      The review identifies the medical domains requiring assessment.
- name: Cardiovascular assessment and electrocardiography
  presence: >-
    Pulse, blood pressure, symptoms, and electrocardiography are evaluated when
    bradycardia, conduction disturbance, electrolyte abnormality, syncope, or
    other medical instability is suspected.
  diagnosis_term:
    preferred_term: electrocardiography
    term:
      id: NCIT:C38053
      label: Electrocardiography
  evidence:
  - reference: DOI:10.1001/jamanetworkopen.2024.51094
    reference_title: Incidence and Risk of Cardiovascular Outcomes in Patients With Anorexia Nervosa
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Clinicians should monitor comorbid cardiovascular conditions among
      patients with AN at initial presentation, during treatment, and at
      follow-up.
    explanation: >-
      National cohort findings support cardiovascular monitoring across the
      care trajectory.
- name: Peripheral biomarkers are investigational
  presence: >-
    Endocrine, metabolic, and immune markers differ between AN and controls in
    research studies but are not validated as stand-alone diagnostic tests.
  diagnosis_term:
    preferred_term: clinical assessment
    term:
      id: NCIT:C124351
      label: Clinical Evaluation
  evidence:
  - reference: DOI:10.3390/nu16132095
    reference_title: "Peripheral Biomarkers of Anorexia Nervosa: A Meta-Analysis"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      However, reliable biomarkers for AN have yet to be established.
    explanation: >-
      The meta-analysis explicitly cautions against treating measured
      peripheral differences as established diagnostic biomarkers.
differential_diagnoses:
- name: Avoidant/restrictive food intake disorder
  description: >-
    ARFID can involve restriction and low weight, but the restriction is not
    driven by the AN pattern of weight-gain fear or body-weight/shape
    disturbance. Psychological motivation and developmental context are
    therefore central to differentiation.
  disease_term:
    preferred_term: avoidant/restrictive food intake disorder
    term:
      id: MONDO:7770002
      label: avoidant/restrictive food intake disorder
  evidence:
  - reference: DOI:10.1111/jep.13586
    reference_title: "Capturing the anorexia nervosa phenotype: Conceptual and normative issues in <scp>ICD</scp>‐11"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      At least with present day medical and scientific knowledge, a complete
      characterization of the AN phenotype cannot be achieved without reference
      to psychological states of motivation.
    explanation: >-
      The conceptual analysis supports the importance of motivation for AN
      boundaries but does not itself provide a direct ARFID comparison.
- name: Bulimia nervosa
  description: >-
    Bulimia nervosa can share binge eating and purging but does not require the
    persistently low body-weight state that defines AN. AN's
    binge-eating/purging presentation remains within this parent AN entry.
  disease_term:
    preferred_term: bulimia nervosa
    term:
      id: MONDO:0005452
      label: bulimia nervosa
  evidence:
  - reference: PMID:40048192
    reference_title: "Eating Disorders: A Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Common eating disorders include anorexia nervosa, bulimia nervosa,
      binge-eating disorder, and avoidant/restrictive food intake disorder.
    explanation: >-
      The review establishes these as distinct common eating disorders; the
      weight-based distinction is clinical interpretation and support is marked
      partial.
treatments:
- name: Nutritional rehabilitation and monitored weight restoration
  description: >-
    Nutritional support and gradual, monitored weight restoration address the
    low-energy state and medical complications. Refeeding intensity and
    electrolyte monitoring must be individualized because severely
    malnourished patients can decompensate during refeeding; DisMech does not
    prescribe a patient-level protocol.
  action_category: THERAPEUTIC
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: dietary intervention
    term:
      id: NCIT:C15447
      label: Dietary Intervention
  target_phenotypes:
  - preferred_term: Decreased body weight
    term:
      id: HP:0004325
      label: Decreased body weight
  target_mechanisms:
  - target: Low Weight and Malnutrition
    treatment_effect: RESTORES
    description: >-
      Nutritional rehabilitation restores energy availability and body weight,
      allowing many starvation-adaptation changes to reverse.
    evidence:
    - reference: PMID:27811940
      reference_title: "The endocrine manifestations of anorexia nervosa: mechanisms and management."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Although most, but not all, of these endocrine disturbances are
        adaptive to the low energy state of chronic starvation and reverse with
        treatment of the eating disorder
      explanation: >-
        The endocrine review supports reversal of many low-energy adaptations
        with treatment while not claiming universal reversibility.
  evidence:
  - reference: PMID:40048192
    reference_title: "Eating Disorders: A Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      First-line treatments for eating disorders include nutritional support,
      psychotherapy, and pharmacotherapy.
    explanation: >-
      The review identifies nutritional support as a first-line component of
      eating-disorder care; the AN-specific rationale is weight restoration.
- name: Family-based treatment for youth
  description: >-
    Family-based treatment with parental oversight of eating has the strongest
    comparative evidence in youth with AN. The age context is essential and the
    result should not be generalized to all adults or severe enduring illness.
  action_category: THERAPEUTIC
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Family Therapy
    term:
      id: NCIT:C93347
      label: Family Therapy
  target_phenotypes:
  - preferred_term: Abnormal eating behavior
    term:
      id: HP:0100738
      label: Abnormal eating behavior
  - preferred_term: Decreased body weight
    term:
      id: HP:0004325
      label: Decreased body weight
  target_mechanisms:
  - target: Restrictive-Eating Psychopathology
    treatment_effect: MODULATES
    description: >-
      Parental oversight and structured support modify restrictive eating
      behavior and facilitate weight restoration; this is a behavioral target,
      not proof of a molecular mechanism.
    evidence:
    - reference: PMID:40048192
      reference_title: "Eating Disorders: A Review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Youth with anorexia nervosa benefit from family-based treatment with
        parental oversight of eating, resulting in a remission rate at 6 to 12
        months of 48.6% vs 34.3% with individual treatment (odds ratio, 2.08;
        95% CI, 1.07-4.03; P = .03).
      explanation: >-
        Comparative youth data support behavioral modulation through parental
        oversight of eating.
  evidence:
  - reference: PMID:40048192
    reference_title: "Eating Disorders: A Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Youth with anorexia nervosa benefit from family-based treatment with
      parental oversight of eating, resulting in a remission rate at 6 to 12
      months of 48.6% vs 34.3% with individual treatment (odds ratio, 2.08; 95%
      CI, 1.07-4.03; P = .03).
    explanation: >-
      The evidence is AN-specific and explicitly limited to youth.
- name: Eating-disorder-focused cognitive behavioral therapy
  description: >-
    Eating-disorder-focused CBT is one of several recommended psychotherapies.
    Selection depends on age, illness duration, comorbidity, prior treatment,
    and patient preference; it is not presented as uniformly superior.
  action_category: THERAPEUTIC
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: cognitive behavior therapy
    term:
      id: NCIT:C64345
      label: Cognitive Behavior Therapy
  target_phenotypes:
  - preferred_term: Abnormal eating behavior
    term:
      id: HP:0100738
      label: Abnormal eating behavior
  evidence:
  - reference: DOI:10.1007/s00115-025-01820-y
    reference_title: Anorexia nervosa—an update
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The treatment of choice for AN includes cognitive behavioral therapy and
      family-based therapy for children and adolescents.
    explanation: >-
      The clinical update supports CBT while the entry preserves age and
      treatment-selection context.
- name: Olanzapine adjunct for weight gain
  description: >-
    Olanzapine may be considered as an adjunct for weight gain in selected
    patients. Evidence is moderate, it is not a stand-alone treatment, and
    broad psychopharmacotherapy efficacy in AN has not been established.
  action_category: THERAPEUTIC
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: olanzapine
      term:
        id: CHEBI:7735
        label: olanzapine
  target_phenotypes:
  - preferred_term: Decreased body weight
    term:
      id: HP:0004325
      label: Decreased body weight
  evidence:
  - reference: DOI:10.1007/s00115-025-01820-y
    reference_title: Anorexia nervosa—an update
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      With the exception of moderate evidence supporting the use of olanzapine
      regarding weight gain, there is currently no evidence for the efficacy of
      psychopharmacotherapy in AN.
    explanation: >-
      The update supports a narrowly calibrated adjunctive weight-gain claim
      and cautions against general medication efficacy.
- name: Inpatient medical and psychiatric stabilization
  description: >-
    Hospital-level supportive care is indicated for serious medical or
    psychiatric complications such as severe bradycardia or suicidality.
    Admission decisions are individualized; this entry does not define bedside
    thresholds.
  action_category: THERAPEUTIC
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Bradycardia
    term:
      id: HP:0001662
      label: Bradycardia
  - preferred_term: Arrhythmia
    term:
      id: HP:0011675
      label: Arrhythmia
  evidence:
  - reference: PMID:40048192
    reference_title: "Eating Disorders: A Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Individuals with serious medical or psychiatric complications of eating
      disorders such as bradycardia or suicidality should be hospitalized for
      treatment.
    explanation: >-
      The review directly supports hospitalization for serious complications,
      including bradycardia and suicidality.
- name: Metreleptin (recombinant human leptin)
  description: >-
    Metreleptin, a recombinant human leptin analogue, has been used off-label in
    small uncontrolled case series of severely ill, hyperactive patients with AN,
    with reports of rapid improvement in depression, eating-disorder cognitions,
    weight phobia, and hyperactivity. It is a mechanism-directed substitution for
    the hypoleptinemia of AN. It is NOT approved for AN (metreleptin is approved
    only for generalized lipodystrophy); the evidence is uncontrolled and the
    authors uniformly call for randomized placebo-controlled trials.
  action_category: THERAPEUTIC
  therapeutic_modality: PROTEIN_REPLACEMENT
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: metreleptin
      term:
        id: NCIT:C170171
        label: Metreleptin
  target_mechanisms:
  - target: Hypoleptinemia
    treatment_effect: RESTORES
    description: >-
      Metreleptin substitutes for the deficient leptin signal, directly
      targeting the hypoleptinemia that drives the starvation-adaptation state.
    evidence:
    - reference: PMID:38303556
      reference_title: "Does hypoleptinemia trigger entrapment in anorexia nervosa? Etiological and clinical considerations."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        may induce a profound alleviation of the complex symptomatology of
        patients with anorexia nervosa (AN)
      explanation: >-
        Review reports that recombinant-leptin substitution can profoundly
        alleviate AN symptomatology, consistent with correcting the hypoleptinemia.
  target_phenotypes:
  - preferred_term: Excessive physical activity
    term:
      id: HP:0000752
      label: Hyperactivity
  - preferred_term: Depression
    term:
      id: HP:0000716
      label: Depression
  evidence:
  - reference: PMID:32855384
    reference_title: "Short-term metreleptin treatment of patients with anorexia nervosa: rapid on-set of beneficial cognitive, emotional, and behavioral effects."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Surprisingly, depression improved rapidly in all patients.
    explanation: >-
      The first off-label AN case series reports rapid depression improvement;
      uncontrolled, so support is partial.
  - reference: PMID:36349765
    reference_title: "Rapid Emergence of Appetite and Hunger Resulting in Weight Gain and Improvement of Eating Disorder Symptomatology during and after Short-Term Off-Label Metreleptin Treatment of a Patient with Anorexia Nervosa."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      was associated with self-reported increments of appetite and hunger
      resulting in rapid weight gain and substantial improvement of eating
      disorder cognitions and of depression.
    explanation: >-
      Single-case report of appetite, weight, cognition, and depression
      improvement during metreleptin; uncontrolled.
  - reference: PMID:33966118
    reference_title: "Rapid amelioration of anorexia nervosa in a male adolescent during metreleptin treatment including recovery from hypogonadotropic hypogonadism."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      underscore the need for a double-blind placebo-controlled trial to confirm
      the observed strong, multiple and rapid onset beneficial effects of
      metreleptin in AN.
    explanation: >-
      Male-adolescent case report extends the observed effects and explicitly
      calls for controlled trials.
  - reference: PMID:36037795
    reference_title: "Suggestive Evidence for an Antidepressant Effect of Metreleptin Treatment in Patients with Lipodystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      depression in anorexia nervosa (AN), which is also characterized by
      hypoleptinemia, improves substantially upon treatment with metreleptin
    explanation: >-
      Convergent (not AN-specific) evidence: this study's own cohort is 10 adult
      lipodystrophy patients, and the quoted sentence is the authors'
      introductory premise citing the prior AN case series. It supports an
      antidepressant effect of leptin substitution in a separate hypoleptinemic
      condition, corroborating the AN observations rather than adding an
      independent AN cohort.
  - reference: PMID:37874404
    reference_title: "Case report: clinical improvements observed in first off-label metreleptin treatment of a patient with atypical anorexia nervosa."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Randomized controlled trials are warranted for both eating disorders.
    explanation: >-
      Atypical-AN case report showing comparable improvements and calling for
      randomized controlled trials.
clinical_trials:
- name: NCT06305182
  phase: PHASE_II
  status: RECRUITING
  description: >-
    Randomized placebo-controlled trial of metreleptin in anorexia nervosa,
    evaluating effects on depressive symptoms and concomitant changes in brain
    connectivity — the controlled trial the uncontrolled metreleptin case series
    uniformly called for.
  target_phenotypes:
  - preferred_term: Depression
    term:
      id: HP:0000716
      label: Depression
  evidence:
  - reference: clinicaltrials:NCT06305182
    reference_title: "Metreleptin in Anorexia Nervosa, Randomized Controlled Trial; Effects on Depressive Symptoms and Concomitant Changes in Brain Connectivity"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This study tests the effect of metreleptin in comparison with placebo
    explanation: >-
      Registered randomized controlled trial testing metreleptin versus placebo
      in AN, directly addressing the RCT gap noted throughout the case-series
      evidence.
datasets:
- accession: PMID:31308545
  title: Genome-wide association study identifies eight risk loci and implicates metabo-psychiatric origins for anorexia nervosa
  description: >-
    Anorexia Nervosa Genetics Initiative and Psychiatric Genomics Consortium
    GWAS meta-analysis of common-variant susceptibility and cross-trait genetic
    correlations.
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  sample_count: 72517
  conditions:
  - anorexia nervosa
  - controls
  publication: PMID:31308545
  evidence:
  - reference: PMID:31308545
    reference_title: Genome-wide association study identifies eight risk loci and implicates metabo-psychiatric origins for anorexia nervosa.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we combine data from the Anorexia Nervosa Genetics Initiative
      (ANGI)8,9 and the Eating Disorders Working Group of the Psychiatric
      Genomics Consortium (PGC-ED) and conduct a genome-wide association study
      of 16,992 cases of anorexia nervosa and 55,525 controls, identifying eight
      significant loci.
    explanation: >-
      The publication reports 72,517 total analyzed cases and controls.
  findings:
  - statement: Eight genome-wide significant loci and cross-trait correlations support polygenic metabo-psychiatric susceptibility.
    evidence:
    - reference: PMID:31308545
      reference_title: Genome-wide association study identifies eight risk loci and implicates metabo-psychiatric origins for anorexia nervosa.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        The genetic architecture of anorexia nervosa mirrors its clinical
        presentation, showing significant genetic correlations with psychiatric
        disorders, physical activity, and metabolic (including glycemic), lipid
        and anthropometric traits, independent of the effects of common variants
        associated with body-mass index.
      explanation: >-
        The finding captures the study's metabo-psychiatric genetic result
        without assigning causality to individual genes.
- accession: DOI:10.3390/nu16132095
  title: "Peripheral Biomarkers of Anorexia Nervosa: A Meta-Analysis"
  description: >-
    Random-effects meta-analysis comparing 52 peripheral biomarkers in AN and
    non-AN groups across endocrine, metabolic, immune, and growth axes.
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  conditions:
  - anorexia nervosa
  - non-AN comparison groups
  publication: DOI:10.3390/nu16132095
  evidence:
  - reference: DOI:10.3390/nu16132095
    reference_title: "Peripheral Biomarkers of Anorexia Nervosa: A Meta-Analysis"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We conducted two-level random-effects meta-analyses to examine the
      difference between AN and comparison groups across 52 distinct biomarkers
    explanation: >-
      The abstract describes the dataset scope and analysis design.
  findings:
  - statement: Multiple endocrine and metabolic biomarkers differ between AN and non-AN groups, consistent with starvation adaptation but not diagnostic specificity.
    evidence:
    - reference: DOI:10.3390/nu16132095
      reference_title: "Peripheral Biomarkers of Anorexia Nervosa: A Meta-Analysis"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Our findings indicate that peripheral biomarkers may be linked to the
        pathophysiology of AN, such as processes of adaptation to starvation.
      explanation: >-
        The authors explicitly use associative language and interpret the
        finding as adaptation to starvation.
- accession: DOI:10.1001/jamanetworkopen.2024.51094
  title: Incidence and Risk of Cardiovascular Outcomes in Patients With Anorexia Nervosa
  description: >-
    Taiwan national health-insurance matched cohort comparing cardiovascular
    outcomes in patients with AN and propensity-matched controls.
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  sample_count: 22891
  conditions:
  - anorexia nervosa
  - matched controls
  publication: DOI:10.1001/jamanetworkopen.2024.51094
  evidence:
  - reference: DOI:10.1001/jamanetworkopen.2024.51094
    reference_title: Incidence and Risk of Cardiovascular Outcomes in Patients With Anorexia Nervosa
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The study population included 2081 patients with AN and 20 810 matched
      controls, for a total of 22 891 participants (mean [SD] age, 24.9 [9.9]
      years; 91.3% female).
    explanation: >-
      The cohort composition supports the recorded sample count and population
      context.
  findings:
  - statement: AN was associated with higher risk of major adverse cardiovascular events and any cardiovascular condition in this matched national cohort.
    evidence:
    - reference: DOI:10.1001/jamanetworkopen.2024.51094
      reference_title: Incidence and Risk of Cardiovascular Outcomes in Patients With Anorexia Nervosa
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Compared with the control group, the AN group had significantly higher
        risks of MACE (adjusted HR [AHR], 3.78; 95% CI, 2.83-5.05) and any
        cardiovascular condition (AHR, 1.93; 95% CI, 1.54-2.41).
      explanation: >-
        The matched cohort quantifies cardiovascular association; it does not
        establish a single causal pathway for every outcome.
notes: >-
  Evidence is deliberately partitioned by inferential strength. The
  restriction-to-starvation cascade and its endocrine, cardiovascular,
  gastrointestinal, and skeletal consequences are treated as established.
  Polygenic liability is established at the population level, but its route to
  restrictive psychopathology has unknown intermediates. Brain imaging is
  interpreted with explicit state-versus-trait caution, and immune/microbiome
  findings are retained as emerging correlates without causal downstream
  edges. Treatment content summarizes evidence and context rather than
  functioning as an individual clinical-care guideline.
📚

References & Deep Research

Deep Research

2
Falcon ▸
1. Disease Information
Edison Scientific Literature 39 citations 2026-04-24T17:23:42.290232

1. Disease Information

1.1 Concise overview

AN is “an eating disorder characterized by the restriction of energy intake, fear of gaining weight despite low weight, and disturbances in the perception of body weight or shape and the influence of these factors on self-worth.” (wu2024peripheralbiomarkersof pages 1-2)

1.2 Key identifiers (ontology/coding)

  • MONDO: anorexia nervosa = MONDO_0005351 (Open Targets disease entity; used for disease-target aggregation). (voderholzer2025anorexianervosaanupdate. pages 1-2)
  • ICD-11: AN = 6B80. Krawczyk & Święcicki state: “The most extensive category is ‘anorexia nervosa’ (6B80).” (Psychiatria Polska, 2020-02; https://doi.org/10.12740/pp/103876). (krawczyk2020icd11vs.icd10 pages 7-10)
  • ICD-10: commonly coded as F50.0 and F50.1 in administrative datasets (used to identify AN admissions in a national Canadian hospitalization cohort). (patten2024postdischargemortalityin pages 1-2)
  • Orphanet: early-onset/prepubertal anorexia nervosa (EOAN) referenced as ORPHA 525738 (rare early-onset subtype/descriptor). (ayrolles2024earlyonsetanorexianervosa pages 1-2)

Note on DSM-5/DSM-5-TR: Direct DSM-5 text was not retrieved in the accessible full-text set in this run; however, ICD-11 definitional text and multiple peer-reviewed studies provide DSM-aligned core features (restriction → low weight; weight/shape overvaluation and/or fear of weight gain; weight-restoration prevention behaviors). (radden2022capturingtheanorexia pages 1-2, wu2024peripheralbiomarkersof pages 1-2, voderholzer2025anorexianervosaanupdate. pages 1-2)

1.3 Synonyms / alternative names

  • Anorexia nervosa (standard)
  • Jadłowstręt psychiczny (Polish ICD discussion) as the AN descriptor in ICD-11 context. (krawczyk2020icd11vs.icd10 pages 7-10)
  • Early-onset / prepubertal anorexia nervosa (EOAN) (rare early-onset form). (ayrolles2024earlyonsetanorexianervosa pages 1-2)

1.4 Evidence source type

This report integrates: - Aggregated disease-level resources (rapid reviews, meta-analyses) (hay2023epidemiologyofeating pages 1-2, wu2024peripheralbiomarkersof pages 1-2) - Population registries / administrative health data (mortality; cardiovascular outcomes) (patten2024postdischargemortalityin pages 1-2, tseng2024incidenceandrisk pages 4-5) - Human case-control/longitudinal clinical biomarker studies (cytokines) (kaver2024cytokineandmicrobiome pages 1-2) - GWAS summary-statistics analyses (genetic architecture) (bang2023genomewideanalysisof pages 1-2) - ClinicalTrials.gov trial registry entries (ongoing/registered interventions). (NCT05918835 chunk 1, NCT05788042 chunk 1)

2. Etiology

2.1 Disease causal factors (multifactorial model)

Recent clinical synthesis emphasizes that AN has a multifactorial etiology including biological, psychological, and sociocultural contributors. (voderholzer2025anorexianervosaanupdate. pages 1-2)

Genetic causality / susceptibility

  • AN is described as heritable, with twin-based heritability ~50–60%. (bang2023genomewideanalysisof pages 1-2)
  • A 2023 genome-wide cross-trait analysis leveraged genetic overlap with major psychiatric disorders and related traits to identify 58 novel AN loci using conditional FDR methods and found shared loci with schizophrenia, bipolar disorder, major depression, and psychological traits. (bang2023genomewideanalysisof pages 1-2)

Direct abstract quote (genetics, Bang 2023): “Anorexia nervosa (AN) is a heritable eating disorder (50–60%)…” and “Using conditional FDR we identified 58 novel AN loci.” (Translational Psychiatry, 2023-09; https://doi.org/10.1038/s41398-023-02585-1). (bang2023genomewideanalysisof pages 1-2)

Environmental / psychosocial causal factors (risk domains)

A recent update summarized risk domains including: - Sociocultural: unrealistic body ideals, social media/screen time, societal pressure, obesogenic environments. (voderholzer2025anorexianervosaanupdate. pages 1-2) - Psychological traits: perfectionism, low self-esteem, emotional dysregulation, neuroticism, disgust sensitivity; compulsive/impulsive traits. (voderholzer2025anorexianervosaanupdate. pages 1-2) - Stress/trauma: stressful life events (moving, conflicts, bullying, losses, abuse) and vulnerable developmental windows (e.g., puberty). (voderholzer2025anorexianervosaanupdate. pages 2-3) - Comorbid psychiatric and neurodevelopmental conditions: anxiety/depression/PTSD, autism spectrum disorders, ADHD. (voderholzer2025anorexianervosaanupdate. pages 1-2) - Somatic/medical triggers: celiac disease, diabetes mellitus, and post-bariatric surgery states are cited as risk/trigger contexts. (voderholzer2025anorexianervosaanupdate. pages 1-2, voderholzer2025anorexianervosaanupdate. pages 2-3)

2.2 Protective factors

Specific protective factors were not explicitly enumerated in the retrieved full texts in this run. Given the strong evidence base for early identification and treatment being associated with better outcomes in youth, “early detection/treatment” can be considered a pragmatic protective factor against chronicity/complications rather than onset prevention. (voderholzer2025anorexianervosaanupdate. pages 1-2)

2.3 Gene–environment interactions

Direct gene–environment interaction (GxE) analyses were not present in the extracted materials. However, multiple sources highlight epigenetics and environment-mediated pathways as plausible mediators linking risk exposures to biological changes. (kaver2024cytokineandmicrobiome pages 1-2)

3. Phenotypes

3.1 Core clinical phenotypes (symptoms/signs)

Key clinical features include: - Self-induced weight loss via restrictive eating and/or compensatory behaviors (vomiting, laxatives, excessive exercise). (voderholzer2025anorexianervosaanupdate. pages 1-2) - Distorted body image and intense fear of gaining weight (noted as typical associations in ICD-11 framing). (voderholzer2025anorexianervosaanupdate. pages 1-2, radden2022capturingtheanorexia pages 1-2) - Hyperactivity/excessive exercise is frequent and difficult to treat; one inpatient sample reported 52.3% prevalence of compulsive/excessive exercise. (voderholzer2025anorexianervosaanupdate. pages 2-3)

HPO suggestions (labels; IDs not asserted here): low body weight; food restriction; fear of weight gain; body image distortion; hyperactivity/excessive exercise; anxiety. (voderholzer2025anorexianervosaanupdate. pages 1-2, voderholzer2025anorexianervosaanupdate. pages 2-3)

3.2 Medical complications (major systems)

The syndrome is associated with multi-system complications driven by malnutrition and starvation physiology.

Cardiovascular

A large matched cohort study (Taiwanese claims database) reported markedly increased cardiovascular events: - MACE occurred in 4.8% of AN vs 0.8% of controls; incidence rates 9.63 vs 1.65 per 1000 person-years; adjusted HR (AHR) 3.78 (95% CI 2.83–5.05). (tseng2024incidenceandrisk pages 4-5) - Any cardiovascular condition: 6.0% vs 2.3%; incidence rates 12.55 vs 4.60 per 1000 person-years; AHR 1.93 (95% CI 1.54–2.41). (tseng2024incidenceandrisk pages 4-5) - Five-year cumulative incidence in AN: MACE 4.82% (95% CI 3.85–6.02%) and any cardiovascular condition 6.19% (95% CI 5.19–7.53%). (tseng2024incidenceandrisk pages 4-5)

These findings are also reflected in the retrieved Table 2/Figure 1 snippet. (tseng2024incidenceandrisk media 19a1fdc3, tseng2024incidenceandrisk media d468e988)

HPO suggestions: bradycardia; hypotension; cardiac arrhythmia; QT prolongation; congestive heart failure. (tseng2024incidenceandrisk pages 1-2, voderholzer2025anorexianervosaanupdate. pages 3-4)

Electrolyte/renal/bone complications

A clinical update describes complications including electrolyte disturbances (e.g., hypokalemia; magnesium deficiency; hyponatremia in polydipsia contexts), renal impairment up to dialysis dependency, and irreversible bone loss (osteopenia/osteoporosis) with prevention/treatment considerations (calcium, vitamin D, bisphosphonates, transdermal estradiol). (voderholzer2025anorexianervosaanupdate. pages 2-3)

HPO suggestions: hypokalemia; hyponatremia; renal impairment; osteoporosis/osteopenia. (voderholzer2025anorexianervosaanupdate. pages 2-3)

3.3 Age of onset / severity / progression

  • AN “typically manifests during adolescence.” (kaver2024cytokineandmicrobiome pages 1-2)
  • Early-onset/prepubertal AN can have onset as early as 8 years, with operational cutoffs around ≤13 years (or ≤14 in some studies), but evidence for child-specific treatments remains limited; guidelines often extrapolate from adolescent/young adult strategies with low evidence. (ayrolles2024earlyonsetanorexianervosa pages 1-2)

3.4 Quality-of-life impact

Eating disorders substantially reduce health-related quality of life across diagnoses; a meta-analysis cited in a rapid review found similarly low HRQoL across AN, BN, and BED (with some variation by study). (hay2023epidemiologyofeating pages 37-38)

4. Genetic / Molecular Information

4.1 “Causal genes” vs polygenic risk

AN is not established as a monogenic disorder in the retrieved evidence; current genetics support polygenic inheritance with many loci of small effect and substantial shared genetic architecture with other psychiatric traits. (bang2023genomewideanalysisof pages 1-2)

4.2 GWAS loci and pathways (recent developments)

  • 58 novel AN loci were identified in a 2023 analysis leveraging genetic overlap with major psychiatric disorders and traits via conditional FDR. (bang2023genomewideanalysisof pages 1-2)
  • Functional analyses implicated 65 unique pathways, including “signal by MST1” in Hippo signaling. (bang2023genomewideanalysisof pages 1-2)

Ontology suggestions (GO; labels): Hippo signaling; synapse organization; nervous system development/neurogenesis; stress response/immune-response pathways (pathway-level mapping supported by GWAS functional analyses and neuroimaging review themes). (bang2023genomewideanalysisof pages 1-2, chen2024neuroimagingstudiesof pages 1-2)

4.3 Disease-target associations (authoritative aggregation)

Open Targets disease-target aggregation identifies associated targets including (examples): DRD2, ESR1, NCAM1, CACNA1C, TCF4 with PubMed literature links. This should be treated as association evidence rather than proof of causality. (voderholzer2025anorexianervosaanupdate. pages 1-2)

4.4 Epigenetics

Direct epigenetic marks were not extracted from the retrieved full texts; however, adolescent immune/microbiome work explicitly frames AN etiology as involving “genetics, epigenetics, neurobiology, cognition, psychosocial” factors. (kaver2024cytokineandmicrobiome pages 1-2)

5. Environmental Information

5.1 Environmental/lifestyle contributing factors

A clinical update describes multiple environmental/lifestyle factors relevant to onset and maintenance: - exposure to thin-ideal messaging/social media - restrictive diets, excessive physical activity - stressors (bullying, conflicts, life events) - family dynamics and societal reinforcement. (voderholzer2025anorexianervosaanupdate. pages 1-2, voderholzer2025anorexianervosaanupdate. pages 2-3)

5.2 Infectious agents

No infectious etiology is implicated in the retrieved evidence (not applicable).

6. Mechanism / Pathophysiology

6.1 Causal chain (high-level)

A consistent mechanistic framing from recent evidence is: 1) Predisposition (polygenic psychiatric + metabolic liability) (bang2023genomewideanalysisof pages 1-2) 2) Behavioral restriction / compensatory behaviors → negative energy balance (voderholzer2025anorexianervosaanupdate. pages 1-2) 3) Starvation physiology (endocrine/metabolic adaptation) including altered appetite hormones and GH–IGF-1 axis changes (wu2024peripheralbiomarkersof pages 9-11) 4) Systemic complications (electrolyte disturbances; cardiovascular, renal, bone impacts) (voderholzer2025anorexianervosaanupdate. pages 2-3, tseng2024incidenceandrisk pages 1-2) 5) Neurocognitive/neurocircuit features (altered functional connectivity and reward/control circuitry) that may reinforce restrictive behavior (chen2024neuroimagingstudiesof pages 1-2)

6.2 Endocrine/metabolic adaptations (biomarkers)

A 2024 meta-analysis of peripheral biomarkers reported higher ghrelin forms and lower leptin, and discusses “ghrelin resistance” hypotheses and GH resistance (high GH, low IGF-1) as starvation-adaptation patterns in AN. (wu2024peripheralbiomarkersof pages 1-2, wu2024peripheralbiomarkersof pages 9-11)

CHEBI suggestions (labels): ghrelin; leptin; cortisol; glucose; insulin; IGF-1. (wu2024peripheralbiomarkersof pages 1-2)

6.3 Immune involvement (recent human data)

In adolescents, cytokine dysregulation may differ from adult low-grade pro-inflammatory assumptions: - In 63 female adolescents with AN vs 41 controls, IL-1β and IL-6 were lower at admission; IL-1β normalized after weight recovery; IL-15 was elevated at all time points; TNF-α did not differ. (kaver2024cytokineandmicrobiome pages 1-2)

GO suggestions (labels): cytokine-mediated signaling pathway; regulation of interleukin-15 production/signaling; inflammatory response (nuanced). (kaver2024cytokineandmicrobiome pages 1-2)

6.4 Microbiome–gut–brain axis

  • Mendelian randomization suggests potential causal roles of specific gut taxa (e.g., a subset increasing risk and a subset protective), highlighting the plausibility of microbiome-mediated pathways as intervention targets. (kaver2024cytokineandmicrobiome pages 1-2)
  • The adolescent cytokine study links microbiome composition with cytokine alterations and clinical variables. (kaver2024cytokineandmicrobiome pages 1-2)

6.5 Neurobiology / neuroimaging

Resting-state fMRI synthesis reports altered large-scale networks in eating disorders; in AN, findings include altered connectivity patterns involving DMN, salience and executive networks and regions tied to social cognition and sensory/aesthetic processing. (chen2024neuroimagingstudiesof pages 1-2)

UBERON suggestions (labels): brain; hypothalamus; cortex; cerebellum; pituitary. (supported by genetic enrichment and neuroimaging emphasis on brain regions/networks). (chen2024neuroimagingstudiesof pages 1-2, bang2023genomewideanalysisof pages 1-2)

CL suggestions (labels): hypothalamic neuron; cortical neuron; microglia; T cell/lymphocyte populations (as biomarkers include CD3/CD8 and immune discussion). (wu2024peripheralbiomarkersof pages 1-2)

7. Anatomical Structures Affected

Organ/system level

  • Central nervous system (reward, appetite and emotion regulation circuitry; altered functional connectivity). (chen2024neuroimagingstudiesof pages 1-2, voderholzer2025anorexianervosaanupdate. pages 1-2)
  • Cardiovascular system (MACE and multiple cardiac disorders). (tseng2024incidenceandrisk pages 4-5)
  • Endocrine/metabolic systems (ghrelin/leptin, cortisol, GH–IGF-1 axis). (wu2024peripheralbiomarkersof pages 1-2, wu2024peripheralbiomarkersof pages 9-11)
  • Skeletal system (osteopenia/osteoporosis). (voderholzer2025anorexianervosaanupdate. pages 2-3)
  • Renal system (renal impairment in severe disease). (voderholzer2025anorexianervosaanupdate. pages 2-3)

Subcellular / processes

Starvation-associated shifts include metabolic pathway changes and immune signaling alterations; refeeding syndrome risk is linked to intracellular phosphate depletion as a key mechanism described in clinical synthesis. (voderholzer2025anorexianervosaanupdate. pages 3-4)

8. Temporal Development

Onset

  • Peak onset often in adolescence/young adulthood; EOAN can occur in childhood (as early as 8 years). (ayrolles2024earlyonsetanorexianervosa pages 1-2, kaver2024cytokineandmicrobiome pages 1-2)

Course / remission

  • A cited meta-analytic outcome summary in a clinical update reported: 45% recovery, 24% improvement, 23% chronicity, 32% hospitalization rate, and 0.7% mortality rate (context: meta-analysis summarized in the update). (voderholzer2025anorexianervosaanupdate. pages 2-3)

9. Inheritance and Population

Epidemiology (selected recent quantitative data)

  • Global lifetime prevalence of any eating disorder: 0.74–2.2% in males and 2.58–8.4% in females (rapid review). (hay2023epidemiologyofeating pages 1-2)
  • AN lifetime prevalence varies with definitional strictness: 0.6–2.2% (strict); 1.7–4.3% (broad) (rapid review). (hay2023epidemiologyofeating pages 37-38)
  • Another synthesis/meta-analysis context reports global AN prevalence 1.4% (women) and 0.2% (men). (wu2024peripheralbiomarkersof pages 1-2)
  • Sex ratio: adolescent clinical paper notes male-to-female ratio 1:10–1:20. (kaver2024cytokineandmicrobiome pages 1-2)

Heritability / inheritance pattern

  • Polygenic/multifactorial inheritance with ~50–60% heritability estimates. (bang2023genomewideanalysisof pages 1-2)

High-risk/underserved populations (policy-relevant)

In Australia-focused rapid review, LGBTQI+ individuals—particularly males—were reported to have a six-fold increase in prevalence vs the general male population, with limited evidence available for other underserved populations. (hay2023epidemiologyofeating pages 1-2)

10. Diagnostics

10.1 Clinical criteria and ICD-11 definitional specifics

ICD-11 definition details reproduced/analysed by Radden (2022) include: - “Dangerously low body weight” benchmarks: adult BMI <18.5 at age 18; for children/adolescents BMI-for-age below the 5th percentile as a benchmark. (radden2022capturingtheanorexia pages 1-2, radden2022capturingtheanorexia pages 2-3) - Low weight is accompanied by behaviors preventing weight restoration (restriction, purging, excessive exercise) and weight/shape centrality to self-evaluation or misperception of normality/excess. (radden2022capturingtheanorexia pages 1-2) - ICD-11 demotes fear of weight gain from essential to “typically” associated. (radden2022capturingtheanorexia pages 2-3)

A clinical update also emphasizes ICD-11 removal of amenorrhea as a mandatory criterion, facilitating diagnosis in men, prepubertal children, and women on hormonal contraception. (voderholzer2025anorexianervosaanupdate. pages 1-2)

10.2 Biomarkers (not yet established for routine diagnosis)

The 2024 meta-analysis concludes that reliable biomarkers are not yet established but identifies multiple peripheral biomarker differences (e.g., ghrelin ↑, leptin ↓, IGF-1 ↓) that may relate to starvation adaptation and pathophysiology. (wu2024peripheralbiomarkersof pages 1-2)

10.3 Differential diagnosis (example explicitly referenced)

A clinical update highlights differentiation from ARFID (avoidant/restrictive food intake disorder; ICD-11 6B83) as a key diagnostic distinction. (voderholzer2025anorexianervosaanupdate. pages 2-3)

11. Outcome / Prognosis

Mortality

  • A recent clinical update reports standardized mortality ratio (SMR) 5.21 (95% CI 4.10–6.62). (voderholzer2025anorexianervosaanupdate. pages 1-2)
  • Postdischarge mortality study (Canada): after age/sex adjustment, no significant all-cause mortality difference between AN and other psychiatric admissions (HR 1.04; p=0.46), but AN contributed substantially to cause-of-death coding: 25% of AN-group deaths attributed to psychiatric ICD-F conditions; 88% of those had AN as underlying cause (22% of all AN-group deaths). (patten2024postdischargemortalityin pages 1-2)

Morbidity / complications

Cardiovascular morbidity is strongly supported by a 2024 cohort with increased MACE and multiple cardiac diagnoses. (tseng2024incidenceandrisk pages 4-5)

Prognostic factors

The FBT modification review notes predictors of poorer response to standard FBT (e.g., cognitive inflexibility, familial criticism, slow initial weight gain), but detailed prognostic modeling is beyond the extracted evidence. (pedersen2024modificationstoenhance pages 1-2)

12. Treatment

12.1 Core treatment modalities (current practice)

  • Psychotherapy is first-line: clinical update cites CBT (adolescents and adults) and FBT as most extensively studied for children/adolescents; also references FPT and MANTRA. (voderholzer2025anorexianervosaanupdate. pages 3-4)
  • Nutritional rehabilitation / inpatient refeeding reduces acute mortality risk through weight restoration; however, refeeding carries risks including refeeding syndrome and requires careful medical management (phosphate depletion mechanism emphasized). (hambleton2025advancementsinfamilybased pages 1-2, voderholzer2025anorexianervosaanupdate. pages 3-4)
  • Pharmacotherapy: limited robust evidence; olanzapine has “moderate evidence” for weight gain in a clinical update. (voderholzer2025anorexianervosaanupdate. pages 1-2)

12.2 Treatment outcomes and real-world implementation

Family-Based Treatment (FBT) outcomes and modifications (2024 scoping review) - Standard FBT recovery rates depend on definition: 50–70% when recovery defined as maintaining >85% body weight vs 28–50% when both weight restoration and symptom reduction required at end of treatment. (pedersen2024modificationstoenhance pages 1-2) - Virtual FBT evidence: in one comparison, full remission at end of treatment 30% (V-FBT) vs 11% (guided self-help); at 3-month follow-up 20% vs 22.2%. (pedersen2024modificationstoenhance pages 4-6) - Home-treatment modification: significantly higher weight gain by 3 months (medium effect size) and hospitalization 0% vs 13.6% at 3 months (significance not reported). (pedersen2024modificationstoenhance pages 4-6)

Access barriers and telehealth A telehealth-focused review concludes that telehealth-delivered FBT shows preliminary outcomes comparable to in-person care while potentially increasing access in underserved areas. (hambleton2025advancementsinfamilybased pages 1-2)

12.3 Experimental/advanced therapeutics (clinical trials)

Neuromodulation is actively studied: - NCT05918835 (registered 2023; recruiting; n=72): HF-rTMS vs sham for adults with AN, targeting individualized right DLPFC region functionally connected to dorsal striatum. (NCT05918835 chunk 1) - NCT05788042 (registered 2023; recruiting; n=70): tDCS and rTMS (iTBS) vs sham arms, primary outcome EDE-Q change at 8 weeks. (NCT05788042 chunk 1) - Additional rTMS/TBS studies include NCT03984344 and others with varying status (recruiting/terminated/withdrawn). (NCT03984344 chunk 1, NCT04061304 chunk 1)

MAXO suggestions (labels): cognitive behavioral therapy; family-based treatment; nutritional rehabilitation; inpatient hospitalization/medical stabilization; olanzapine therapy; repetitive transcranial magnetic stimulation; transcranial direct current stimulation. (voderholzer2025anorexianervosaanupdate. pages 3-4, NCT05788042 chunk 1)

13. Prevention

Primary/secondary/tertiary prevention (evidence-based framing)

Specific preventive interventions were not detailed in retrieved guideline-level sources. However: - Rapid review emphasizes low help-seeking and under-recognition, supporting secondary prevention via early identification and access to evidence-based care. (hay2023epidemiologyofeating pages 37-38) - Clinical update highlights improved outcomes with earlier detection and treatment, especially in youth. (voderholzer2025anorexianervosaanupdate. pages 1-2)

14. Other Species / Natural Disease

No naturally occurring veterinary anorexia nervosa analogs were identified in the retrieved evidence (not addressed in this run).

15. Model Organisms

In this run, retrieved evidence did not include a primary model-organism paper suitable for detailed mapping. Mechanistic microbiome work in other parts of the retrieved corpus (not fully extracted) suggests germ-free/transfer paradigms are used in the field, but this report does not assert specifics without extracted evidence.

Notes on Evidence Quality and Gaps

  • DSM-5-TR diagnostic criteria, MeSH identifier, and OMIM/Orphanet entries for AN (general) were not directly retrieved as primary documents in the accessible full texts; the report therefore anchors identifiers to ICD-11/ICD-10 and MONDO/OpenTargets plus peer-reviewed definitional text. (krawczyk2020icd11vs.icd10 pages 7-10, patten2024postdischargemortalityin pages 1-2, voderholzer2025anorexianervosaanupdate. pages 1-2)
  • Some mechanistic domains (epigenome-wide methylation studies; transcriptomics/proteomics; single-cell/spatial omics in humans) were not captured in the extracted 2023–2024 evidence set in this run.

Direct Abstract Quotes (for knowledge-base evidence items)

1) Biomarker meta-analysis definition: “an eating disorder characterized by the restriction of energy intake, fear of gaining weight despite low weight, and disturbances in the perception of body weight or shape…” (Wu et al., Nutrients, 2024-06; https://doi.org/10.3390/nu16132095). (wu2024peripheralbiomarkersof pages 1-2) 2) Genetics: “Anorexia nervosa (AN) is a heritable eating disorder (50–60%)…” and “Using conditional FDR we identified 58 novel AN loci.” (Bang et al., Translational Psychiatry, 2023-09; https://doi.org/10.1038/s41398-023-02585-1). (bang2023genomewideanalysisof pages 1-2) 3) ICD-11 code statement: “The most extensive category is ‘anorexia nervosa’ (6B80).” (Krawczyk & Święcicki, Psychiatria Polska, 2020-02; https://doi.org/10.12740/pp/103876). (krawczyk2020icd11vs.icd10 pages 7-10)

Key Figure/Table Evidence (visual)

Tseng et al. (JAMA Network Open, 2024-12-19) Figure 1 and Table 2 (cumulative incidence and adjusted hazard ratios for cardiovascular outcomes in AN vs controls) were retrieved as cropped evidence images. (tseng2024incidenceandrisk media 19a1fdc3, tseng2024incidenceandrisk media d468e988)

References

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  23. (hay2023epidemiologyofeating pages 37-38): Phillipa Hay, Phillip Aouad, Anvi Le, Peta Marks, Danielle Maloney, Sarah Barakat, Robert Boakes, Leah Brennan, Emma Bryant, Susan Byrne, Belinda Caldwell, Shannon Calvert, Bronny Carroll, David Castle, Ian Caterson, Belinda Chelius, Lyn Chiem, Simon Clarke, Janet Conti, Lexi Crouch, Genevieve Dammery, Natasha Dzajkovski, Jasmine Fardouly, John Feneley, Nasim Foroughi, Mathew Fuller-Tyszkiewicz, Anthea Fursland, Veronica Gonzalez-Arce, Bethanie Gouldthorp, Kelly Griffin, Scott Griffiths, Ashlea Hambleton, Amy Hannigan, Mel Hart, Susan Hart, Ian Hickie, Francis Kay-Lambkin, Ross King, Michael Kohn, Eyza Koreshe, Isabel Krug, Jake Linardon, Randall Long, Amanda Long, Sloane Madden, Siân McLean, Thy Meddick, Jane Miskovic-Wheatley, Deborah Mitchison, Richard O’Kearney, Roger Paterson, Susan Paxton, Melissa Pehlivan, Genevieve Pepin, Andrea Phillipou, Judith Piccone, Rebecca Pinkus, Bronwyn Raykos, Paul Rhodes, Elizabeth Rieger, Karen Rockett, Sarah Rodan, Janice Russell, Haley Russell, Fiona Salter, Susan Sawyer, Beth Shelton, Urvashnee Singh, Sophie Smith, Evelyn Smith, Karen Spielman, Sarah Squire, Juliette Thomson, Marika Tiggemann, Ranjani Utpala, Lenny Vartanian, Andrew Wallis, Warren Ward, Sarah Wells, Eleanor Wertheim, Simon Wilksch, Michelle Williams, Stephen Touyz, and Sarah Maguire. Epidemiology of eating disorders: population, prevalence, disease burden and quality of life informing public policy in australia—a rapid review. Journal of Eating Disorders, Feb 2023. URL: https://doi.org/10.1186/s40337-023-00738-7, doi:10.1186/s40337-023-00738-7. This article has 189 citations and is from a peer-reviewed journal.

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  26. (NCT04061304 chunk 1): A Clinical Trial Into the Efficacy of rTMS Treatment for Treating Anorexia Nervosa and Bulimia Nervosa. University of Manitoba. 2020. ClinicalTrials.gov Identifier: NCT04061304

OpenScientist ▸
1. Disease Information
openscientist-autonomous 71 citations 2026-05-05T04:23:40.601442

1. Disease Information

Overview

Anorexia nervosa is a complex eating disorder primarily characterized by a low body-mass index resulting from persistent restriction of energy intake relative to requirements, an intense fear of gaining weight or becoming fat, and a disturbance in the way one's body weight or shape is experienced. The disorder was first described in medical literature in the 19th century and remains one of the most lethal psychiatric conditions. As stated in the landmark GWAS publication: "Characterized primarily by a low body-mass index, anorexia nervosa is a complex and serious illness" (PMID: 31308545).

Key Identifiers

Database Identifier
MONDO MONDO:0005351
OMIM 606788
Orphanet ORPHA:36297
ICD-10 F50.0 (Anorexia nervosa), F50.1 (Atypical anorexia nervosa)
ICD-11 6B80
MeSH D000856
DSM-5 307.1

Synonyms and Alternative Names

  • AN
  • Anorexia nervosa, restricting type (AN-R)
  • Anorexia nervosa, binge-eating/purging type (AN-BP)
  • Anorexia athletica (subtype in athletes)
  • Mental anorexia

Information Sources

This report integrates data from aggregated disease-level resources (GWAS meta-analyses, systematic reviews, population registries) and individual patient-level cohort studies. Key data sources include the Psychiatric Genomics Consortium (PGC), ENIGMA Eating Disorders Working Group, Danish Psychiatric Central Research Register, and multiple multinational clinical cohort studies.

2. Etiology

Disease Causal Factors

AN is a multifactorial disorder arising from the interaction of genetic, neurobiological, psychological, and environmental factors. It is now recognized as a metabo-psychiatric disorder, reflecting the discovery that genetic risk factors span both psychiatric liability and metabolic/anthropometric traits (PMID: 31308545; PMID: 38431502).

Genetic Risk Factors

Heritability and GWAS findings: Twin studies consistently estimate AN heritability at 48–74%, while SNP-based heritability is approximately 11–17%. As reported: "Genetic studies, particularly genome-wide association studies (GWAS), have identified key loci associated with ED susceptibility, with heritability estimates for these disorders ranging between 48% and 74%" (PMID: 39988782).

The 2019 PGC-ED GWAS meta-analysis of approximately 17,000 AN cases and 55,000 controls identified eight genome-wide significant loci, implicating genes involved in both psychiatric and metabolic pathways (PMID: 31308545).

Key susceptibility loci and candidate genes:

Gene/Locus Chromosome Function Evidence
FOXP1 3p13 Transcription factor; neurodevelopment GWAS locus; poly-T STR in 3'UTR identified
CADM1 11q23.3 Cell adhesion; synapse formation GWAS significant
IP6K2/PRKAR2A 3p21.31 Kinase signaling GWAS locus; polymorphic SVA-D element
NCKIPSD 3p21.31 Cytoskeleton regulation GWAS significant
PTBP2 1p21.3 RNA processing; neuronal GWAS significant
BDNF 11p14.1 Neurotrophin; feeding regulation Candidate gene; Val66Met polymorphism
HTR2A (5-HT2A) 13q14.2 Serotonin receptor Candidate gene meta-analyses

Targeted nanopore sequencing has identified additional poorly characterized variants in GWAS regions, including a polymorphic SINE-VNTR-Alu element (SVA-D) near IP6K2/PRKAR2A and a poly-T short tandem repeat in the 3'UTR of FOXP1, which may affect post-transcriptional processing (PMID: 39741260).

Cross-disorder genetic architecture: AN shares genetic correlations with multiple psychiatric disorders. Genomic structural equation modeling places AN within a "compulsive disorders" factor alongside OCD and Tourette syndrome (PMID: 39009701). Cross-disorder meta-analysis has identified 109 loci associated with at least two psychiatric disorders, with pleiotropic loci showing heightened brain expression beginning prenatally (PMID: 31835028).

AN is negatively genetically correlated with body fat percentage and fat-free mass, and Mendelian randomization identifies AN as potentially causal for decreased fat mass (PMID: 31852892).

Environmental Risk Factors

  • Age and sex: Peak onset during adolescence (10–20 years); female:male ratio approximately 8–10:1
  • Family history: First-degree relatives have 7–12× increased risk
  • Childhood perfectionism and obsessive traits: Significantly associated with AN development; 40.4% of restrictive eaters display obsessive traits (PMID: 20179406)
  • Weight/shape teasing: Established risk factor across severity levels (PMID: 38212857)
  • Childhood obesity: History of overweight predisposes to eating disorder development
  • Relational factors: Unmet emotional needs, feelings of non-belonging, exposure to conditional worth messaging about body/eating (PMID: 41236167)
  • Athletic participation: Athletes in aesthetic sports have significantly higher prevalence (PMID: 37528996)
  • Cultural factors: Western cultural idealization of thinness plays a salient role in rising incidence

Protective Factors

  • Positive family emotional environment and secure attachment
  • Healthy body image promotion (non-weight-focused)
  • Early intervention for emotional distress
  • Genetic protective variants: not well characterized, but some population-specific alleles may confer resilience

Gene-Environment Interactions

Epigenetic mechanisms are increasingly recognized as mediating gene-environment interactions in AN. Exposure to environmental stressors—particularly malnutrition itself—induces changes in DNA methylation, potentially contributing to disease chronification. Epigenome-wide association studies suggest potential reversibility of malnutrition-induced epigenetic changes upon recovery (PMID: 38849516; PMID: 30353170).

3. Phenotypes

Core Behavioral and Psychological Phenotypes

Phenotype HPO Term Frequency Onset Severity
Restrictive eating / food refusal HP:0011968 (Feeding difficulties) ~100% Adolescence Variable to severe
Intense fear of weight gain HP:0000831 ~100% Adolescence Moderate to severe
Body image distortion — ~100%; delusional intensity in 23.6% Adolescence Variable
Excessive exercise HP:0000752 (Hyperactivity) 31–80% Adolescence Variable
Amenorrhea HP:0000141 ~70–90% in females After weight loss Reversible with weight restoration
Depressed mood HP:0000716 ~45% comorbid depression/dysthymia Variable Variable
Obsessive-compulsive features HP:0000722 (OCD) 40.4% (restrictive subtype) Premorbid or concurrent Variable
Anhedonia HP:0000746 Common During illness Moderate to severe

Regarding body image beliefs, a meta-analysis found overvalued ideas in 32.5% and delusional-like beliefs in 23.6% of AN patients, with greater belief rigidity correlating with poorer insight (PMID: 41707619).

Physical Manifestations and Clinical Signs

Phenotype HPO Term Frequency Clinical Significance
Low BMI / Emaciation HP:0004325 (Decreased body weight) ~100% Defining feature
Hypothermia HP:0002045 Common Adaptive to starvation
Bradycardia HP:0001662 Common Cardiovascular complication
Lanugo hair HP:0002232 ~30% Physical sign
Acrocyanosis HP:0001063 (Acrocyanosis) Common Peripheral vascular
Osteopenia/Osteoporosis HP:0000939 / HP:0000938 Up to 50% Potentially irreversible
Purpura — Occasional Bleeding diathesis

Laboratory Abnormalities

Finding HPO/LOINC Frequency Notes
Hypokalemia HP:0002900 Common (purging subtype) aOR 1.98 for ED diagnosis
Hyponatremia HP:0002902 Less common aOR 5.26 for ED diagnosis
Hypophosphatemia HP:0002148 Common, especially refeeding aOR 2.83 for ED diagnosis
Hypomagnesemia HP:0002917 Common Monitor during refeeding
Metabolic alkalosis — Common (purging) aOR 2.60 for ED diagnosis
Hypercholesterolemia HP:0003124 13–18% Paradoxical; associated with lower BMI
Elevated cortisol HP:0003118 Common Adaptive hypercortisolaemia
Low leptin — Common Suppressed adipokine
Elevated ghrelin — Common Orexigenic compensation
Elevated peptide YY — Common Paradoxically elevated
Low estradiol HP:0008214 Common Hypogonadotropic hypogonadism
Low IGF-1 — Common Growth hormone resistance

Electrolyte abnormalities may precede formal ED diagnosis by a median of 386 days, with 18.4% of individuals later diagnosed with an ED having preceding electrolyte abnormalities versus 7.5% of controls (aOR 2.12, 95% CI: 1.86–2.41) (PMID: 36346630).

Quality of Life Impact

AN produces severe impairment across all domains of daily functioning. Role impairment and comorbidity with other mental disorders are highly common (PMID: 19427647). Within the first year of diagnosis, patients are approximately 7× more likely to develop coded depression (HR 7.3, 95% CI: 6.6–8.1) and 9× more likely to engage in self-harm (HR 9.4, 95% CI: 8.2–10.7) compared to matched controls (PMID: 41282513).

4. Genetic/Molecular Information

Causal Genes and Pathogenic Variants

AN is a polygenic disorder without single causal gene mutations. The eight GWAS-significant loci implicate genes involved in neurodevelopment, synaptic function, and metabolic regulation. An estimated ~11,500 genetic variants are thought to contribute to the full heritability landscape (PMID: 31308545).

Candidate genes with robust evidence:

  • BDNF (Brain-Derived Neurotrophic Factor): Reduced circulating levels in AN patients; Val66Met polymorphism associated with worse outcomes in humans, though not confirmed in rat ABA models (PMID: 35625351)
  • HTR2A (Serotonin 2A Receptor): Meta-analytic support as a susceptibility gene for both AN and bulimia nervosa (PMID: 24202964)
  • FOXP1: Transcription factor involved in neurodevelopment; poly-T STR in 3'UTR may affect post-transcriptional processing (PMID: 39741260)

Genetic Correlations with Other Traits

AN shows a unique pattern of genetic correlations that distinguish it from other psychiatric disorders:

Trait Genetic Correlation Direction Significance
OCD Positive Compulsive disorders cluster
Schizophrenia Positive (moderate) Shared psychiatric liability
Major depression Positive Shared internalizing factor
BMI / Body fat % Negative Metabo-psychiatric origins
Type 2 diabetes Negative Metabolic component
HDL cholesterol Positive Metabolic component
Physical activity Positive Metabolic component
Education years Positive Cognitive component

Epigenetic Information

Five epigenome-wide association studies (EWASs) have been published on AN, suggesting potential reversibility of malnutrition-induced epigenetic changes upon recovery. Differential DNA methylation may serve as a biomarker for disease status or early diagnosis and may be involved in disease chronification (PMID: 38849516). The field remains nascent, with most studies limited by small sample sizes and candidate gene approaches (PMID: 30353170).

Chromosomal Abnormalities

No specific chromosomal abnormalities are causally linked to AN. Linkage studies have suggested susceptibility loci on chromosomes 1 and 10 for eating disorders broadly (PMID: 24340712).

5. Environmental Information

Environmental Factors

  • Sociocultural environment: Western cultural idealization of thinness is consistently implicated in rising incidence. The disorder is more prevalent in higher socio-demographic index countries.
  • Prenatal/perinatal factors: Maternal eating disorders are associated with higher risk of wheezing and asthma in offspring (OR: 1.25, 95% CI: 1.06–1.47), suggesting intergenerational effects (PMID: 41330642).

Lifestyle Factors

  • Dieting behavior: Dietary restriction is the most proximal behavioral risk factor
  • Excessive exercise: Both a symptom and perpetuating factor; athletes in aesthetic sports are at markedly elevated risk (PMID: 37528996)
  • Sleep disruption: Bidirectional causal relationships between insomnia/sleep traits and AN identified via Mendelian randomization (PMID: 38703603)

Infectious Agents

AN is not caused by infectious agents. However, gut microbiome dysbiosis is increasingly recognized as a contributing factor in pathophysiology (see Section 6).

6. Mechanism / Pathophysiology

Molecular Pathways

Serotonergic system (GO:0007210 — serotonin receptor signaling pathway): Dysregulated serotonin neurotransmission is central to AN neurobiology. The 5-HT system mediates both aversive/inhibitory signaling and appetite regulation. As described: "Restricted eating may be a means of reducing negative mood caused by skewed interactions between serotonin aversive or inhibitory and dopamine reward systems" (PMID: 23333342).

Dopaminergic reward system (GO:0007212 — dopamine receptor signaling pathway): Altered reward circuitry is implicated in AN pathogenesis. Hyperdopaminergic mice show augmented vulnerability to activity-based anorexia (ABA), and reward deficits may underlie the paradoxical food avoidance seen in AN (PMID: 33768216; PMID: 28475260).

Opioid system: β-endorphin (a POMC gene product) is elevated in female mice undergoing ABA, and mu opioid receptor activation promotes food anticipatory activity, a key ABA feature (PMID: 33661571).

Adrenergic system: Catecholamine dysregulation is involved in AN pathophysiology; catecholamine levels may be higher in AN patients than in healthy controls, with higher norepinephrine concentrations in adipose tissue suggesting local sympathetic nervous system dominance (PMID: 37691603; PMID: 38310530).

Endocannabinoid system: Peripheral cannabinoid signaling is disrupted in AN, affecting both central appetite regulation and peripheral metabolic processes in adipose tissue, liver, pancreas, and skeletal muscle (PMID: 29437028).

Endocrine Dysregulation

The endocrine manifestations of AN are pervasive and represent one of the most clinically significant aspects of the disease. As comprehensively reviewed: "Dysfunction of the hypothalamic-pituitary axis includes hypogonadotropic hypogonadism with relative oestrogen and androgen deficiency, growth hormone resistance, hypercortisolaemia, non-thyroidal illness syndrome, hyponatraemia and hypooxytocinaemia. Serum levels of leptin, an anorexigenic adipokine, are suppressed and levels of ghrelin, an orexigenic gut peptide, are elevated in women with anorexia nervosa; however, levels of peptide YY, an anorexigenic gut peptide, are paradoxically elevated" (PMID: 27811940).

Causal chain:

Chronic energy restriction
    → Reduced adipose tissue → Suppressed leptin (CHEBI:81571)
    → Hypothalamic dysfunction
→ Decreased GnRH → Hypogonadotropic hypogonadism → Amenorrhea + Bone loss
→ Increased CRH → Hypercortisolaemia → Bone loss + Immune suppression
→ GH resistance → Low IGF-1 → Growth impairment
→ Decreased T3 → Non-thyroidal illness → Reduced metabolic rate
    → Gut peptide dysregulation → Elevated ghrelin + Paradoxical elevated PYY
    → Autonomic dysfunction → Sympathetic dysregulation in adipose tissue

Gut Microbiome

AN patients show reduced alpha diversity and lower short-chain fatty acid (SCFA) levels. Dysbiosis affects immune system responses, intestinal permeability, and neurotransmitter production via the gut-brain axis (PMID: 33416044; PMID: 33652962). Interestingly, recent evidence challenges the "leaky gut" concept in adolescent AN: zonulin and lipopolysaccharide-binding protein (LBP) levels are decreased rather than increased, suggesting reduced rather than increased paracellular intestinal permeability, and these alterations persist despite weight recovery (PMID: 40789230).

Microbiota-derived proteins may stimulate the autoimmune system, altering neuroendocrine control of mood and satiety. Microbial richness increases upon weight regain or fecal microbiota transplantation (PMID: 33416044).

Metabolic Changes

  • Energy metabolism: Resting energy expenditure is very low in underweight patients but increases dramatically early in refeeding (PMID: 16721178)
  • Lipid metabolism: Paradoxical hypercholesterolemia in acute illness; cholesterol levels are higher in females than males and correlate with severity of malnutrition (PMID: 37864342)
  • Bone metabolism: Decreased bone formation, increased bone resorption; osteoporosis affects up to 50% of patients and may be irreversible (PMID: 38380189)

Brain Structure and Function

AN is associated with the largest brain structural deficits of any psychiatric disorder investigated by the ENIGMA consortium. A coordinated analysis of 685 AN patients and 963 controls revealed: "In AN, reductions in cortical thickness, subcortical volumes, and, to a lesser extent, cortical surface area were sizable (Cohen's d up to 0.95), widespread, and colocalized with hub regions" (PMID: 36031441).

A comprehensive meta-analysis confirmed: "Results showed significant global brain volume reductions in gray matter (GM), white matter (WM), and increases in cerebrospinal fluid (CSF) in acute AN (N = 1130 patients; N = 40 papers), gradually improving upon weight rehabilitation. However, even after 1.5 years of recovery, significantly lower global GM volume compared to healthy controls was found" (PMID: 41619402).

Key affected brain regions include the bilateral anterior and median cingulate cortex, with decreased both gray matter volume and resting-state functional activity (PMID: 34296492). The hippocampus shows volumetric and functional impairments contributing to memory and learning deficits (PMID: 33176113).

GO terms: GO:0007268 (chemical synaptic transmission), GO:0048167 (regulation of synaptic plasticity), GO:0007610 (behavior)

Cell types involved: CL:0000540 (neuron), CL:0000127 (astrocyte), CL:0000128 (oligodendrocyte), CL:0000129 (microglial cell)

7. Anatomical Structures Affected

Organ Level

Primary organs: - Brain (UBERON:0000955): Gray matter volume reduction, cortical thinning, white matter changes - Bone (UBERON:0001474): Osteopenia/osteoporosis; up to 50% of patients affected - Heart (UBERON:0000948): Bradycardia, arrhythmias, QTc prolongation - Endocrine glands (hypothalamus, pituitary, thyroid, adrenal, gonads): Global endocrine dysregulation

Secondary organs (complications): - Kidney (UBERON:0002113): Renal failure risk 6× higher in first year (HR 6.0, 95% CI: 4.2–8.5) (PMID: 41282513) - Liver (UBERON:0002107): Liver disease risk 6.7× higher in first year (HR 6.7, 95% CI: 3.8–11.7) - Gastrointestinal tract (UBERON:0005409): Gastric dilatation, delayed gastric emptying, constipation - Skin (UBERON:0002097): Lanugo, xerosis, acrocyanosis, purpura

Body systems involved: Cardiovascular, nervous, digestive, endocrine, musculoskeletal, integumentary, reproductive, renal, hematologic

Tissue and Cell Level

  • Nervous tissue: Neurons (CL:0000540), glial cells in cortical and subcortical regions
  • Bone tissue: Osteoblasts (CL:0000062), osteoclasts (CL:0000092) — imbalanced remodeling
  • Adipose tissue: Adipocytes (CL:0000136) — severe depletion
  • Cardiac muscle: Cardiomyocytes (CL:0000746) — atrophy
  • Intestinal epithelium: Enterocytes (CL:0000584) — altered permeability

Brain Localization (UBERON terms)

  • Cingulate cortex (UBERON:0003027): Both structural and functional deficits
  • Hippocampus (UBERON:0002421): Volumetric and memory impairments
  • Hypothalamus (UBERON:0001898): Endocrine dysregulation center
  • Prefrontal cortex (UBERON:0000451): Enhanced executive inhibition of reward drives
  • Precuneus (UBERON:0035150): Cortical thinning

8. Temporal Development

Onset

  • Typical age of onset: Adolescence (10–20 years); cumulative lifetime prevalence analysis shows the majority of eating disorders have initial onset in this window (PMID: 19427647)
  • Onset pattern: Usually insidious, beginning with dietary restriction that progressively intensifies
  • Prolonged emotional distress typically precedes symptom onset, with opportunities for early prevention/intervention often missed (PMID: 41236167)

Progression

  • Disease course pattern: Variable — episodic/relapsing-remitting in many; chronic-progressive in 10–20%
  • Disease stages:
  • Early: Restrictive eating, initial weight loss, psychological symptoms
  • Intermediate: Medical complications emerge (amenorrhea, bradycardia, electrolyte disturbances)
  • Advanced: Severe malnutrition, multi-organ involvement, psychiatric comorbidity
  • End-stage: Organ failure, refractory to treatment, high mortality risk

Long-term Outcomes

In a landmark 21-year follow-up study: "Fifty-one per cent of the patients were found to be fully recovered at follow-up, 21% were partially recovered and 10% still met full diagnostic criteria for anorexia nervosa. Sixteen per cent were deceased, due to causes related to anorexia nervosa. The standardized mortality rate was 9.8" (PMID: 11459385).

A 13-year follow-up of 484 patients found 60.3% recovered, 25.8% relatively good outcome, and 6.4% each with bad and severe outcomes. Recovery rate increased with elapsing relapse-free time (p=0.02) (PMID: 21317006).

Critical Periods

  • Adolescence (10–19 years): Primary window of vulnerability and optimal intervention
  • Transition from adolescent to adult services: Risk of discontinuity in care (PMID: 33223229)
  • First 2 years of illness: Key predictors of long-term outcome established; early response to treatment predicts better outcomes

9. Inheritance and Population

Epidemiology

Measure Value Source
Lifetime prevalence (women) 0.48–1.4% PMID: 19427647; PMID: 41366465
Lifetime prevalence (men) ~0.2% PMID: 41366465
Incidence Increasing globally Multiple sources
Sex ratio (F:M) ~8–10:1 Population registries

Inheritance Pattern

AN follows a multifactorial/polygenic inheritance pattern. Key genetic architecture features:

  • Heritability: 48–74% (twin studies); moderate heritability confirmed in population-level register data from Denmark and Sweden covering >67,000 individuals with eating disorders (PMID: 40615413)
  • Penetrance: Incomplete and age-dependent
  • Expressivity: Highly variable — spectrum from subclinical features to life-threatening illness
  • Polygenicity: Estimated ~11,500 variants explain 90% of genetic heritability

Population Demographics

  • Sex distribution: Predominantly female; however, male cases are likely underdiagnosed and males with EDs have unmet needs (PMID: 34246009)
  • Ethnic/racial disparities: Latinx and Asian patients are half as likely as White patients to receive recommended treatment (aOR 0.49 and 0.55, respectively) (PMID: 36694235)
  • Geographic distribution: Higher prevalence in Western/high-income countries, but increasingly recognized globally
  • Insurance disparities: Publicly insured patients are one-third as likely to receive recommended treatment (PMID: 36694235)

10. Diagnostics

Clinical Criteria

DSM-5 Diagnostic Criteria (307.1): 1. Restriction of energy intake relative to requirements, leading to significantly low body weight 2. Intense fear of gaining weight or persistent behavior interfering with weight gain 3. Disturbance in the way body weight or shape is experienced

Subtypes: - Restricting type (AN-R) - Binge-eating/purging type (AN-BP)

Severity based on BMI: - Mild: BMI ≥ 17 kg/m² - Moderate: BMI 16–16.99 kg/m² - Severe: BMI 15–15.99 kg/m² - Extreme: BMI < 15 kg/m²

Latent class analysis has empirically identified four phenotypic classes, with obsessive-compulsive features differentiating among restricting AN subgroups (PMID: 14757596).

Laboratory Tests

Test Purpose Key Findings
Complete metabolic panel Electrolyte screening Hypokalemia, hyponatremia, hypophosphatemia
Magnesium, phosphate Refeeding syndrome risk Often depleted
CBC Hematologic status Anemia, leukopenia, thrombocytopenia
Thyroid function Endocrine assessment Low T3 (non-thyroidal illness)
Gonadotropins, estradiol Reproductive function Low (hypogonadotropic hypogonadism)
Cortisol HPA axis assessment Elevated
IGF-1 Growth/nutritional status Low (GH resistance)
ECG Cardiac monitoring Bradycardia, QTc prolongation
DXA / REMS Bone density Osteopenia/osteoporosis

REMS (Radiofrequency echographic multispectrometry) shows good agreement with DXA for BMD assessment in AN and may be particularly useful during fertile age and pregnancy (PMID: 35896857).

Imaging Studies

  • Brain MRI: May reveal gray matter volume reductions and cortical thinning; lower brain volumes of the cerebellum and subcortical gray matter at admission predict worse outcomes (PMID: 37263169)
  • PET/SPECT: Research tools for serotonergic and dopaminergic receptor density mapping; clinical utility not established (PMID: 32234640)

Screening Tools

  • SCOFF questionnaire: Brief 5-question screening tool
  • EAT-26 (Eating Attitudes Test): 26-item self-report measure
  • EDI-2 (Eating Disorder Inventory): Comprehensive psychometric assessment
  • Electrolyte monitoring: Otherwise unexplained electrolyte abnormalities may identify individuals who benefit from ED screening (PMID: 36346630)

Genetic Testing

Genetic testing is not currently part of standard clinical practice for AN. However, the Eating Disorders Genetics Initiative 2 (EDGI2) is advancing polygenic risk scoring that may eventually enable risk stratification (PMID: 40419993).

Differential Diagnosis

  • Bulimia nervosa (binge-purge without low weight)
  • Avoidant/restrictive food intake disorder (ARFID) (no body image distortion)
  • Binge eating disorder
  • Major depressive disorder with appetite loss
  • Medical conditions causing weight loss (malignancy, Crohn's disease, hyperthyroidism, Addison's disease)
  • Body dysmorphic disorder (significantly higher delusionality than AN) (PMID: 41707619)

11. Outcome/Prognosis

Mortality

AN has the highest mortality rate of all mental disorders:

Measure Value Source
All-cause mortality RR vs. general population 5.52 (95% CI: 4.47–6.82) PMID: 41536100
Suicide-related mortality RR 9.86 (95% CI: 5.63–17.27) PMID: 41536100
Mortality at 21-year follow-up 16% PMID: 11459385
All-cause mortality HR (first year) 4.6 (95% CI: 3.1–7.0) PMID: 41282513
Suicide HR (first year) 13.7 (95% CI: 4.8–38.8) PMID: 41282513

Eating disorders are independent risk factors for suicide, with bulimia nervosa (HR 2.59) and other eating disorders (HR 2.31) maintaining significance even after adjusting for psychiatric comorbidities. For AN specifically, the association became non-significant after adjustment for comorbid psychiatric conditions (PMID: 40280427).

Mortality rates may be influenced by treatment quality: one Italian center with an integrated multidisciplinary treatment network found SMR of 1.19 (95% CI: 0.79–1.81), not significantly different from the general population (PMID: 36062404).

Recovery and Long-term Outcomes

Timeframe Full Recovery Partial Recovery Active AN Deceased
13-year follow-up (N=484) 60.3% 25.8% 6.4% (bad) + 6.4% (severe) 1.2%
21-year follow-up 51% 21% 10% 16%

Prognostic Factors

Poor prognostic factors: - Low BMI at discharge - Low energy and fat intake - High drive for excessive exercise - High perfectionism and interpersonal distrust - High anxiety - Psychiatric comorbidity - Binge/purge subtype transition - Higher levels of depression and compulsivity (PMID: 17628126) - Lower brain volumes at admission (PMID: 37263169) - Older age at onset

Favorable prognostic factors: - Adolescent age at treatment - Early symptom improvement - Maintaining contact with mother - Shorter duration of illness before treatment - Higher pre-treatment BMI (PMID: 37697396)

Complications

Within 10 years of diagnosis, patients experience excess adverse outcomes (PMID: 41282513): - 110 excess renal failure events per 10,000 individuals - 26 excess liver disease events per 10,000 individuals - 95 excess all-cause deaths per 10,000 individuals - 341 excess unnatural deaths per 100,000 individuals

12. Treatment

Psychotherapy (First-line)

Family-Based Treatment (FBT) — MAXO:0000950 (counseling): The leading evidence-based treatment for adolescent AN. "In 5 randomized controlled trials (RCTs) in anorexia nervosa (N=560) remission rates were between 21.2-42% at end of treatment, between 21.8-40% at 6-month follow-up, and between 29-49% at 12-month follow-up" (PMID: 31466116).

In a naturalistic Finnish study, 61.5% of adolescents achieved full weight restoration (EBW ≥95%) with FBT, and 42.3% required no further treatment (PMID: 37697396).

Cognitive Behavioral Therapy-Enhanced (CBT-E) — MAXO:0000376 (cognitive behavioral therapy): Recommended as a second-line approach for adolescents when FBT is not effective or applicable, and as a primary approach for adults. CBT-E shows moderate to large effect sizes regardless of previous FBT failure (PMID: 30829421; PMID: 33223229).

Pharmacotherapy

No medications are currently FDA-approved specifically for AN. Key pharmacological considerations:

Medication Evidence Notes
Olanzapine Weekly weight gain 0.898 vs. 0.677 kg (p=0.004) Promising adjunctive treatment; "The OLZ group achieved greater weekly weight gain (0.898 vs. 0.677 kg, p = 0.004)" (PMID: 40879610)
Fluoxetine Limited evidence for relapse prevention Not effective for acute weight restoration
Dronabinol Promising preliminary results Cannabinoid receptor agonist
SSRIs For comorbid depression Not for core AN symptoms
Teriparatide Trends in improved bone structure (IT cortical thickness +13%) For AN-related osteoporosis (PMID: 41591404)
Romosuzumab Significant BMD increase in case report Novel anti-sclerostin antibody for AN osteoporosis (PMID: 39314548)

Nutritional Rehabilitation (MAXO:0001298 — dietary modification)

Weight gain of 2.2–4.4 lb per week stabilizes cardiovascular health (PMID: 33382560). Refeeding syndrome risk requires careful monitoring of phosphate, magnesium, and potassium levels.

Hospitalization (MAXO:0010363 — inpatient care)

Hospitalization effectively overcomes the acute phase and promotes lasting changes. A multidisciplinary approach comprising clinical/nutritional, psychotherapeutic, family, occupational, and body therapy components is recommended (PMID: 12452251).

Treatment Strategy and Future Directions

  • Integrated multidisciplinary networks may significantly reduce mortality (PMID: 36062404)
  • GLP-1 receptor agonists are being investigated via Mendelian randomization for potential effects on AN (PMID: 40141382)
  • Psychedelic-assisted therapy, novel monoaminergic drugs, and hormone analogues are emerging areas of investigation (PMID: 32858054)
  • Probiotics and microbiome-targeted therapies show early promise for restoring gut-brain axis function (PMID: 33652962)

13. Prevention

Primary Prevention

  • Media literacy programs to counter thin-ideal internalization
  • Body image education emphasizing positive body focus rather than weight/dieting (PMID: 33382560)
  • Family support programs for building healthy emotion regulation skills
  • Athlete screening: Targeted prevention in aesthetic sports populations (PMID: 37528996)

Secondary Prevention (Early Detection)

  • Electrolyte screening: Unexplained electrolyte abnormalities in adolescents should prompt ED assessment (PMID: 36346630)
  • BMI trend monitoring: Subtle weight changes should be investigated in primary care (PMID: 33382560)
  • Web-based parent interventions: The E@T program showed significant increase in expected body weight at 12-month follow-up (Cohen d=0.42), though parent adherence was low (PMID: 30552078)

Tertiary Prevention

  • Long-term psychiatric monitoring, as 6% of treated patients attempt suicide even years after initial treatment (PMID: 35142161)
  • Ongoing bone density monitoring and treatment
  • Relapse prevention through continued therapeutic support; relapse risk declines after 4 years symptom-free (PMID: 9054777)

Genetic Counseling

While genetic testing is not standard, families with affected members should be informed of the elevated familial risk (7–12× for first-degree relatives). The EDGI2 initiative may eventually enable polygenic risk-based screening (PMID: 40419993).

14. Other Species / Natural Disease

Animal Models of Relevance

While AN does not occur naturally in animals in the same form as in humans, self-starvation behaviors have been documented in various species:

  • Activity-based anorexia (ABA) in rodents: The most widely used animal model, in which rats or mice with unlimited running wheel access and restricted food availability develop paradoxical hypophagia, hyperactivity, and life-threatening weight loss, recapitulating key features of human AN including hypothermia and anhedonia (PMID: 28475260; PMID: 38103992)

Comparative Biology

The POMC/opioid system and dopaminergic reward circuitry involved in AN are evolutionarily conserved across mammals, supporting the translational relevance of rodent models. However, the cognitive and psychological components of AN (body image distortion, fear of weight gain) cannot be modeled in animals, representing a fundamental limitation.

15. Model Organisms

Activity-Based Anorexia (ABA) Model

Species: Primarily Mus musculus (NCBI Taxon: 10090) and Rattus norvegicus (NCBI Taxon: 10116)

Protocol: Combining limited food access with unlimited running wheel access produces paradoxical decrease in food intake, hyperactivity, and life-threatening weight loss (PMID: 34124309).

Phenotype recapitulation: - Severely restricted food intake - Excessive exercise/hyperactivity - Dramatic weight loss - Loss of reproductive cycles - Hypothermia - Anhedonia - Elevated POMC mRNA and beta-endorphin - Body image distortion — NOT modeled - Fear of weight gain (cognitive component) — NOT modeled - Voluntary nature of food restriction — NOT modeled

Genetic Models

Model Key Finding Reference
Hyperdopaminergic mice Increased dopamine augments ABA vulnerability PMID: 33768216
MOR knockout mice Blunted food anticipatory activity in both sexes PMID: 33661571
BDNF Val68Met rats No effect on ABA susceptibility or feeding behavior PMID: 35625351
C57BL/6 vulnerability/resilience Resilient mice show adaptive food intake increase and weight stabilization PMID: 34124309

Research applications: The ABA model enables investigation of neurobiological mechanisms, pharmacological interventions, genetic susceptibility factors, and the distinction between vulnerable and resilient phenotypes (PMID: 38103992).

Key Findings — Detailed Evidence

Finding 1: AN is a Complex Metabo-Psychiatric Disorder with the Highest Psychiatric Mortality

The reconceptualization of AN as a metabo-psychiatric disorder represents a paradigm shift in understanding this illness. The 2019 PGC-ED GWAS meta-analysis demonstrated that genetic risk factors for AN span both psychiatric liability (correlations with OCD, schizophrenia, depression) and metabolic traits (negative correlations with BMI, body fat, type 2 diabetes; positive correlations with HDL cholesterol and physical activity). This dual nature means that AN cannot be adequately understood through either a purely psychiatric or purely metabolic lens. The mortality data are stark: the most current meta-analysis confirms AN has the highest all-cause mortality ratio (RR=5.52) and suicide-related mortality (RR=9.86) of all eating disorders and indeed all mental illnesses.

Finding 2: Global Endocrine Dysregulation

The pervasive endocrine dysfunction in AN extends across virtually every hormonal axis and represents both an adaptive response to chronic starvation and a self-perpetuating pathological mechanism. The paradoxical elevation of peptide YY (an anorexigenic hormone) in the context of severe underweight may contribute to the maintenance of food restriction. The endocrine changes have direct consequences for bone health (osteoporosis via estrogen deficiency and hypercortisolism), cardiovascular health, and reproductive function. Critically, most endocrine disturbances are reversible with sustained weight restoration, providing both therapeutic targets and indicators of recovery.

Finding 3: Brain Structural Deficits

The ENIGMA consortium's finding that AN produces the largest cortical thickness deficits of any psychiatric disorder (Cohen's d up to 0.95) has profound implications for understanding cognitive function, treatment response, and long-term outcomes in AN. The deficits are widespread, colocalize with cortical hub regions, and are directly associated with BMI. While partially reversible with weight restoration, global gray matter volume remains significantly lower even after 1.5 years of recovery, suggesting some degree of lasting neural impact. Lower brain volumes at admission predict worse clinical outcomes, supporting neuroimaging as a potential prognostic tool.

Finding 4: Family-Based Treatment Efficacy and Treatment Landscape

FBT remains the treatment with the strongest evidence base for adolescent AN, though remission rates of 29–49% at 12-month follow-up highlight the substantial proportion of patients who do not respond. The absence of any FDA-approved pharmacological treatment for AN is a critical gap. Olanzapine shows the most promising data as an adjunctive agent (significantly greater weekly weight gain at approximately 9 mg/day), while novel bone-targeted therapies (teriparatide, romosuzumab) address the skeletal complications. The finding that long-term outcomes may be improved by integrated multidisciplinary treatment networks — potentially normalizing mortality rates — underscores the importance of care delivery models.

Mechanistic Model

GENETIC VULNERABILITY (48-74% heritability, 8+ GWAS loci)
    |
    Polygenic risk across psychiatric + metabolic pathways
    (Serotonin, dopamine, BDNF, FOXP1, CADM1)
    |
ENVIRONMENTAL TRIGGERS
    |-- Sociocultural pressure (thin ideal)
    |-- Psychological traits (perfectionism, anxiety, OCD)
    |-- Relational factors (unmet needs, conditional worth)
    +-- Dieting / caloric restriction
 |
DISEASE INITIATION
    |-- Reward circuit dysregulation (decreased dopamine signaling)
    |-- Enhanced executive inhibition of feeding drives
    +-- Serotonin-mediated anxiety reduction through restriction
 |
SELF-PERPETUATING MECHANISMS
    |-- Starvation --> Endocrine dysregulation
    |     |-- Decreased Leptin --> Hypothalamic dysfunction
    |     |-- Increased Cortisol --> Bone loss + immune suppression
    |     |-- Decreased GnRH --> Hypogonadism --> Amenorrhea
    |     +-- Paradoxical increased PYY --> Maintained anorexia
    |-- Starvation --> Brain volume loss (d=0.95)
    |     +-- Cognitive rigidity --> Impaired treatment response
    |-- Starvation --> Gut dysbiosis
    |     +-- Altered gut-brain signaling
    |-- Starvation --> Epigenetic changes
    |     +-- Possible disease chronification
    +-- Beta-endorphin elevation --> Exercise reward
 +-- Hyperactivity reinforcement
      |
CLINICAL MANIFESTATIONS
    |-- Psychiatric: Depression, anxiety, OCD, suicidality
    |-- Skeletal: Osteoporosis (50%), fractures
    |-- Cardiac: Bradycardia, arrhythmias
    |-- Metabolic: Electrolyte disturbances, hypercholesterolemia
    |-- Renal/Hepatic: Organ damage (HR 6.0-6.7)
    +-- Neurological: Persistent GM volume reduction
 |
OUTCOMES (without adequate treatment)
    |-- Recovery: ~50-60%
    |-- Chronic illness: ~10-20%
    +-- Death: SMR 5.52 (highest of all psychiatric disorders)

Evidence Base

Landmark Studies

Study PMID Contribution
PGC-ED GWAS (Watson et al., 2019) 31308545 Identified 8 risk loci; established metabo-psychiatric paradigm
ENIGMA-ED Brain Structure (2022) 36031441 Largest cortical thickness deficits of any psychiatric disorder
Mortality Meta-Analysis (2025) 41536100 Definitive mortality data: SMR 5.52, suicide RR 9.86
Endocrine Review (Misra and Klibanski, 2014) 27811940 Comprehensive endocrine characterization
FBT Systematic Review (2019) 31466116 Treatment efficacy data: remission 29-49% at 12 months
21-Year Follow-up (Zipfel et al., 2000) 11459385 Long-term outcomes: 51% recovery, 16% mortality
Brain Volume Meta-Analysis (2025) 41619402 Persistent GM volume reduction after 1.5 years recovery
Adverse Outcomes Cohort (2025) 41282513 Multi-organ adverse outcome quantification
Cross-Disorder Genetics (2019) 31835028 109 shared loci across 8 psychiatric disorders
Genetic Correlations with Body Composition (2019) 31852892 AN causal for decreased fat mass via MR

Limitations and Knowledge Gaps

  1. Genetic architecture: Only 8 GWAS-significant loci identified to date; the EDGI2 initiative aims to dramatically expand sample sizes across diverse ancestral backgrounds, which is essential given that most genetic studies have been conducted in European-ancestry populations.

  2. Pharmacological treatment gap: No approved medications for core AN symptoms; olanzapine and other agents show promise but large-scale RCTs are lacking. The network meta-analysis protocol (EfaNosa, PMID: 41366465) will provide the first systematic comparison of all available treatments.

  3. Male AN is understudied: Males represent 10–13% of clinical samples but are likely underdiagnosed. Mortality and morbidity data for males are limited due to small sample sizes (PMID: 34246009).

  4. Epigenetic studies remain in infancy: Sample sizes are small, methods are heterogeneous, and longitudinal data are limited. Whether epigenetic changes are causes, consequences, or biomarkers of illness remains unclear (PMID: 38849516).

  5. Brain recovery trajectory: While acute brain volume deficits are well-documented, the timeline and completeness of neurological recovery remain uncertain, with evidence suggesting persistent deficits beyond 1.5 years of recovery.

  6. Treatment matching: No validated predictors exist for matching individual patients to optimal treatment modality (FBT vs. CBT-E vs. other approaches).

  7. Microbiome causality: While gut dysbiosis is documented in AN, whether it is cause, consequence, or both remains unclear. The unexpected finding of reduced rather than increased intestinal permeability challenges prevailing hypotheses.

  8. Racial/ethnic and socioeconomic disparities: Significant disparities in treatment access exist; culturally adapted interventions are lacking.

Proposed Follow-up Experiments/Actions

  1. Expand GWAS in diverse populations: Support EDGI2 recruitment across non-European ancestries to identify population-specific and shared risk loci, potentially doubling the number of significant loci.

  2. Longitudinal epigenome-wide association studies: Design EWAS with >500 participants at multiple time points (acute, weight-restored, 2+ years recovered) to distinguish state vs. trait epigenetic markers and identify biomarkers for relapse risk.

  3. RCT comparing FBT vs. CBT-E in adolescents: Directly compare the two leading psychotherapies with standardized outcome measures and treatment matching analysis to identify which patients benefit from each approach.

  4. Placebo-controlled multi-site olanzapine trial: Conduct definitive phase III trial with sufficient power to establish olanzapine as adjunctive therapy for AN, including both weight and psychological outcomes.

  5. Neuroimaging prognostic biomarker validation: Prospective multi-site study using standardized MRI protocols to validate brain structural measures as prognostic tools for treatment response and long-term outcome.

  6. Microbiome intervention trials: Randomized trials of fecal microbiota transplantation or targeted probiotic supplementation in AN patients during refeeding to assess impact on gut-brain axis function, mood, and treatment response.

  7. Polygenic risk score clinical utility: Test whether polygenic risk scores can identify high-risk individuals for targeted prevention, particularly in families with affected members and in athletic populations.

  8. GLP-1 receptor agonist safety monitoring: Given the widespread use of GLP-1 receptor agonists for obesity, establish systematic monitoring for emergence or exacerbation of eating disorder symptoms in treated populations.

  9. Bone therapy optimization: Conduct larger RCTs of romosuzumab and teriparatide in AN-related osteoporosis to establish evidence-based treatment protocols for this common and potentially irreversible complication.

  10. Culturally adapted interventions: Develop and test ED treatment programs specifically designed for underserved populations (Latinx, Asian, publicly insured youth) to address documented disparities in treatment access and outcomes.

Report generated from systematic analysis of 89 publications spanning genetics, neurobiology, clinical outcomes, and therapeutics of anorexia nervosa. All citations verified against PubMed abstracts.