Irritable Bowel Syndrome

Complex MONDO:0005052 Pathograph 5 Show in embeddings browser Gastrointestinal Disease

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder defined by recurrent abdominal pain associated with altered bowel habits in the absence of structural disease. Its pathophysiology reflects disordered gut-brain axis signaling, including visceral hypersensitivity, gut dysmotility, low-grade mucosal immune activation with mast cell involvement, intestinal barrier dysfunction, and microbiome dysbiosis. Patients are classified by predominant stool pattern (diarrhea-predominant, constipation-predominant, or mixed), and management targets symptoms through diet, the microbiome, and gut-brain modulation.

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6
Pathophys.
6
Phenotypes
5
Pathograph
2
Genes
13
Medical Actions
4
Datasets
5
References
2
Deep Research
C

Comorbidities

Hypermobile Ehlers-Danlos Syndrome <-> Irritable Bowel Syndrome
Disease B UNKNOWN CANDIDATE
⚙

Pathophysiology

6
Visceral Hypersensitivity
Enhanced perception of normal gut sensations leads to pain and discomfort. Lowered pain thresholds in response to balloon distension. Central sensitization contributes.
Pain Perception GO:0048265 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves Pain Perception, annotated with response to pain (GO:0048265). GO:0048265 is a biological process from the Gene Ontology.
Show evidence (4 references)
PMID:18252749 SUPPORT
"A significant 3.5-fold increase in median numbers of TRPV1-immunoreactive fibres was found in biopsies from IBS patients compared with controls (p<0.0001)."
TRPV1-expressing sensory nerve fibers are significantly increased in IBS, providing a molecular basis for visceral hypersensitivity.
PMID:18252749 SUPPORT
"In multivariate regression analysis, only TRPV1-immuno-reactive fibres (p = 0.005) and mast cells (p = 0.008) were significantly related to the abdominal pain score."
TRPV1 nerve fiber density directly correlates with abdominal pain severity in IBS patients.
PMID:17241857 SUPPORT In Vitro
"Mediators from IBS patients, but not controls, markedly enhanced the firing of mesenteric nerves (14.7 +/- 3.2 imp/sec vs 2.8 +/- 1.5 imp/sec; P < .05) and stimulated mobilization of Ca(2+) in dorsal root ganglia neurons (29% +/- 4% vs 11% +/- 4%; P < .05)."
Mucosal mediators from IBS patients directly excite visceral sensory neurons, demonstrating a mechanism for visceral hypersensitivity.
+ 1 more reference
Gut Dysmotility
Altered intestinal motility patterns with either accelerated (diarrhea-predominant) or delayed (constipation-predominant) transit. Abnormal colonic contractions.
enterochromaffin cell CL:0000577 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves enterochromaffin cell, annotated with type EC enteroendocrine cell (CL:0000577). CL:0000577 is a cell type from the Cell Ontology.
Gut Motility GO:0030432 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves Gut Motility, annotated with peristalsis (GO:0030432). GO:0030432 is a biological process from the Gene Ontology.
Show evidence (2 references)
PMID:15100164 SUPPORT
"5-HT release from enterochromaffin (EC) cells initiates peristaltic, secretory, vasodilatory, vagal and nociceptive reflexes."
Serotonin from enterochromaffin cells is a key regulator of intestinal motility and peristaltic reflexes.
PMID:15100164 SUPPORT
"5-HT directly and indirectly affects intestinal motor and secretory function and abnormalities may lead to either constipation or diarrhea."
Dysregulated serotonin signaling can account for both IBS-D and IBS-C subtypes through effects on motility.
Gut-Brain Axis Dysfunction
Bidirectional communication between gut and brain is disrupted. Stress and psychological factors modulate gut function through autonomic and neuroendocrine pathways.
Nervous System Process GO:0050877 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves Nervous System Process (GO:0050877). GO:0050877 is a biological process from the Gene Ontology.
Show evidence (2 references)
PMID:37048642 SUPPORT
"Although the pathophysiology of IBS has not been fully elucidated, it involves dysregulation of communication between the brain and gut (brain-gut axis) which is associated with alterations in intestinal motility, gut permeability, visceral hypersensitivity and gut microbiota composition."
The gut-brain axis is a central organizing principle in IBS pathophysiology, integrating multiple dysfunctional mechanisms.
PMID:15100164 SUPPORT
"Ongoing, bidirectional brain-gut interactions involving 5-HT pathways occur that significantly influence the effector systems."
Serotonin pathways mediate bidirectional brain-gut communication in IBS.
Intestinal Barrier Dysfunction
Increased intestinal permeability (leaky gut) allows translocation of luminal antigens, triggering low-grade immune activation. Mucosal disruption encompasses alterations in epithelial and mucus layers. Barrier restoration via dietary, microbial, and pharmacological interventions is emerging as a therapeutic strategy.
Show evidence (5 references)
PMID:17593135 SUPPORT
"While a subgroup of patients with IBS appears to have evidence of increased intestinal permeability, improvements in the methods and validation are key to further research in this field in order to better understand intestinal barrier functions in IBS."
A subset of IBS patients demonstrate measurable increases in intestinal permeability, though the exact prevalence varies by methodology.
PMID:19595511 SUPPORT
"Approximately 39% of diarrhea-predominant IBS patients had increased intestinal membrane permeability as measured by the lactulose/mannitol ratio."
Nearly 40% of IBS-D patients show objective evidence of barrier dysfunction using validated permeability testing.
PMID:19595511 SUPPORT
"A subset of D-IBS patients had increased intestinal membrane permeability that was associated with an increased FBDSI score and increased hypersensitivity to visceral and thermal nociceptive pain stimuli."
Barrier dysfunction in IBS-D correlates with more severe symptoms and heightened visceral sensitivity, linking permeability to clinical phenotype.
+ 2 more references
Immune Activation and Mast Cell Degranulation
Low-grade mucosal immune activation with increased mast cell density and degranulation near enteric nerves. Mast cell mediators including histamine and tryptase excite visceral sensory neurons, contributing to pain and hypersensitivity.
mast cell CL:0000097 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves mast cell (CL:0000097). CL:0000097 is a cell type from the Cell Ontology.
Mast Cell Activation GO:0045576 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves Mast Cell Activation (GO:0045576). GO:0045576 is a biological process from the Gene Ontology.
Show evidence (3 references)
PMID:17241857 SUPPORT
"IBS-dependent nerve firing and Ca(2+) mobilization were correlated with the area of the colonic lamina propria occupied by mast cells (r = 0.74; P < .01, and r = 0.78; P < .01, respectively)."
Mast cell density directly correlates with sensory neuron activation in IBS, establishing a quantitative relationship.
PMID:17241857 SUPPORT In Vitro
"Mucosal mast cell mediators from IBS patients excite rat nociceptive visceral sensory nerves. These results provide new insights into the mechanism underlying visceral hypersensitivity in IBS."
Mast cell mediators from IBS patients directly activate nociceptive neurons, providing a mechanistic link to pain.
PMID:18252749 SUPPORT
"Substance P-immunoreactive fibres (p = 0.01), total nerve fibres (PGP9.5) (p = 0.002), mast cells (c-kit) (p = 0.02) and lymphocytes (CD3) (p = 0.03) were also significantly increased in the IBS group."
Both mast cells and immune cells are increased in IBS mucosa, indicating low-grade immune activation.
Microbiome Dysbiosis
Altered composition and function of gut microbiota may contribute to symptoms. Post-infectious IBS follows gastroenteritis in some patients. Genus-level composition is modifiable by dietary fermentable substrate: adding high-amylose resistant starch to a low-FODMAP diet shifts composition and enriches the resistant-starch degrader Ruminococcus E. Whether such a shift moves the community toward a healthy-donor reference is untested, as the trials reporting it carry no healthy-control arm.
Host-Microbiome Interaction GO:0044003 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves Host-Microbiome Interaction, annotated with symbiont-mediated perturbation of host process (GO:0044003). GO:0044003 is a biological process from the Gene Ontology.
Show evidence (2 references)
PMID:37048642 SUPPORT Other
"Although the pathophysiology of IBS has not been fully elucidated, it involves dysregulation of communication between the brain and gut (brain-gut axis) which is associated with alterations in intestinal motility, gut permeability, visceral hypersensitivity and gut microbiota composition."
Names altered gut microbiota composition as a component of IBS pathophysiology, which is the claim of this node.
PPR:PPR1298203 Preprint · not peer-reviewed SUPPORT INDIRECT Human Clinical
"A specific mix of fibres can increase fibre intake, improve gut microbiota and gastrointestinal-specific anxiety without impacting sleep and symptoms of IBS patients on a low FODMAP diet as compared with placebo, despite no changes found in faecal and blood biomarkers."
Small randomised trial (n=26, 13 per arm; non-peer-reviewed preprint) showing that genus-level community composition in IBS shifts measurably when a high-amylose resistant starch blend is added to a low-FODMAP diet. Indirect support for this node: it demonstrates the community is modifiable by dietary substrate rather than measuring dysbiosis against a healthy reference, for which the trial has no control arm.
⬡

Pathograph

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

Phenotypes

6
Digestive 4
Altered Bowel Habits VERY_FREQUENT Abnormal gastrointestinal motility HP:0030895 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Altered bowel habits, annotated with Abnormal gastrointestinal motility (HP:0030895). HP:0030895 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:15100164 SUPPORT
"5-HT directly and indirectly affects intestinal motor and secretory function and abnormalities may lead to either constipation or diarrhea."
Dysregulated serotonergic control of gut motility underlies the alternating and altered bowel habits characteristic of IBS.
Bloating VERY_FREQUENT Abdominal distention HP:0003270 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abdominal Distention (HP:0003270). HP:0003270 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:24076059 SUPPORT
"Bloating, pain, and passage of wind also were reduced while IBS patients were on the low-FODMAP diet."
Bloating is a cardinal IBS symptom, here shown to be modifiable by reducing fermentable carbohydrate intake.
Constipation FREQUENT 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.
IBS-C subtype
Show evidence (1 reference)
PMID:22986437 SUPPORT
"The objective of this trial was to determine the efficacy and safety of linaclotide treatment in patients with irritable bowel syndrome with constipation (IBS-C) over 26 weeks."
Constipation defines the IBS-C subtype and is the target symptom for the guanylate cyclase-C agonist linaclotide.
Diarrhea FREQUENT HP:0002014 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Diarrhea (HP:0002014). HP:0002014 is a phenotype from the Human Phenotype Ontology.
IBS-D subtype
Show evidence (2 references)
PMID:19595511 SUPPORT
"Approximately 39% of diarrhea-predominant IBS patients had increased intestinal membrane permeability as measured by the lactulose/mannitol ratio."
Increased intestinal permeability is present in a substantial proportion of IBS-D patients and may contribute to diarrheal symptoms.
PMID:15100164 SUPPORT
"5-HT directly and indirectly affects intestinal motor and secretory function and abnormalities may lead to either constipation or diarrhea."
Dysregulated serotonin signaling affects secretion and motility, contributing to diarrhea in IBS-D.
Constitutional 2
Abdominal Pain VERY_FREQUENT HP:0002027 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abdominal Pain (HP:0002027). HP:0002027 is a phenotype from the Human Phenotype Ontology.
Related to defecation
Show evidence (2 references)
PMID:18252749 SUPPORT
"Increased TRPV1 nerve fibres are observed in IBS, together with a low-grade inflammatory response. The increased TRPV1 nerve fibres may contribute to visceral hypersensitivity and pain in IBS, and provide a novel therapeutic target."
TRPV1-expressing nerve fibers are increased in IBS and directly linked to abdominal pain severity.
PMID:17241857 SUPPORT In Vitro
"IBS-dependent excitation of dorsal root ganglia was inhibited by histamine H(1) receptor blockade and serine protease inactivation (inhibition of 51.7%; P < .05 and 74.5%; P < .05; respectively)."
Mast cell mediators, particularly histamine and proteases, directly excite nociceptive neurons to produce abdominal pain in IBS.
Fatigue FREQUENT HP:0012378 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Fatigue (HP:0012378). HP:0012378 is a phenotype from the Human Phenotype Ontology.
🧬

Genetic Associations

2
HTR3E (Risk Factor)
Gene: HTR3E hgnc:24005 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is HTR3E (hgnc:24005). hgnc:24005 is a gene from the HUGO Gene Nomenclature Committee.
SCN5A (Risk Factor)
Gene: SCN5A hgnc:10593 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is SCN5A (hgnc:10593). hgnc:10593 is a gene from the HUGO Gene Nomenclature Committee.
💊

Medical Actions

13
Dietary Modification
Low FODMAP diet effective in many patients.
Show evidence (1 reference)
PMID:24076059 SUPPORT Human Clinical
"In a controlled, cross-over study of patients with IBS, a diet low in FODMAPs effectively reduced functional gastrointestinal symptoms."
Randomized cross-over trial evidence that a low-FODMAP diet reduces IBS symptoms, supporting it as a first-line dietary intervention.
Soluble Fiber (Psyllium)
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
Supplementation with soluble fiber (psyllium/ispaghula husk) as a first-line treatment to improve global symptoms and abdominal pain in IBS. Unlike insoluble fiber (bran), soluble psyllium provides adequate symptom relief and is recommended by guidelines as a bulking agent for IBS.
Show evidence (2 references)
PMID:19713235 SUPPORT Human Clinical
"Psyllium offers benefits in patients with irritable bowel syndrome in primary care."
Primary-care randomised controlled trial showing that soluble fiber (psyllium), unlike insoluble bran, gives adequate symptom relief in adult IBS.
PPR:PPR1275071 Preprint · not peer-reviewed SUPPORT Human Clinical
"A 12-week trial of psyllium fiber improves pain in most and gives sustained relief in three-fourths of children with FAP-NOS and IBS."
Pediatric randomised placebo-controlled trial (non-peer-reviewed preprint; corroborating the adult primary-care RCT) reporting that psyllium fiber improves and sustains pain relief in children with IBS and functional abdominal pain.
High-Amylose Resistant Starch and Psyllium Blend
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
Supplementation of an established low-FODMAP diet with a blend of high-amylose maize resistant starch (HAMS) and psyllium husk, as an adjunct aimed at the microbial cost of FODMAP restriction rather than at symptom control. Distinct from psyllium monotherapy: the single trial reporting it used a psyllium-matched placebo, so the effects below are the incremental effect of the resistant-starch component on a psyllium background, not an effect of psyllium. Investigational — one small unreplicated preprint trial, with no guideline standing.
Mechanism Target:
MODULATES Microbiome Dysbiosis — The resistant-starch component supplies fermentable substrate lost under FODMAP restriction, shifting genus-level composition and enriching the primary resistant-starch degrader Ruminococcus E. Recorded as MODULATES rather than RESTORES because the trial reports compositional change against a psyllium-matched placebo, not movement toward a healthy-donor reference.
Show evidence (1 reference)
PPR:PPR1298203 Preprint · not peer-reviewed SUPPORT Human Clinical
"This relative abundance was greater than that of the placebo group at T2"
Reports the compositional shift this link asserts, in the arm receiving the resistant-starch blend.
Show evidence (2 references)
PPR:PPR1298203 Preprint · not peer-reviewed SUPPORT Human Clinical
"ur gut® improved GI-specific anxiety (P = 0.01) and sexual subscale of QOL (P = 0.018)."
Randomised double-blind trial (n=26, 13 per arm; non-peer-reviewed preprint) reporting improved GI-specific anxiety and the sexual subscale of quality of life in the blend arm. The comparator contained an identical psyllium dose, so this is the incremental effect of the resistant-starch component.
PPR:PPR1298203 Preprint · not peer-reviewed SUPPORT Human Clinical
"observed intervention effects were not due to psyllium husk, the placebo incorporated"
Establishes that psyllium was controlled out by design, which is why this is curated as a separate treatment rather than as further support for the psyllium entry.
Antispasmodics
Dicyclomine, hyoscyamine for pain and cramping.
Show evidence (1 reference)
PMID:40307155 SUPPORT Other
"Antispasmodics (alone or combined) are used as first-line therapy for pain management, whereas antidiarrheals, such as loperamide, are used for reducing diarrhea in diarrhea-predominant IBS (IBS-D) and laxatives are used for constipation in constipation-predominant IBS (IBS-C)."
The guideline positions antispasmodics, alone or combined, as first-line therapy for pain management in irritable bowel syndrome.
Loperamide
For diarrhea-predominant IBS.
Show evidence (1 reference)
PMID:40307155 SUPPORT Other
"Antispasmodics (alone or combined) are used as first-line therapy for pain management, whereas antidiarrheals, such as loperamide, are used for reducing diarrhea in diarrhea-predominant IBS (IBS-D) and laxatives are used for constipation in constipation-predominant IBS (IBS-C)."
The guideline positions antidiarrheals such as loperamide as therapy for reducing diarrhea in diarrhea-predominant IBS.
Linaclotide
Guanylate cyclase agonist for IBS-C.
Show evidence (1 reference)
PMID:22986437 SUPPORT Human Clinical
"Linaclotide 290 μg once daily significantly improved abdominal and bowel symptoms associated with IBS-C over 26 weeks of treatment."
Phase 3 RCT demonstrating linaclotide efficacy for abdominal and bowel symptoms in IBS-C.
Rifaximin
Non-absorbable antibiotic for IBS-D with bloating.
Show evidence (1 reference)
PMID:21208106 SUPPORT Human Clinical
"Among patients who had IBS without constipation, treatment with rifaximin for 2 weeks provided significant relief of IBS symptoms, bloating, abdominal pain, and loose or watery stools."
The TARGET phase 3 trials show the minimally absorbed antibiotic rifaximin relieves global IBS symptoms and bloating in non-constipated IBS.
Tricyclic Antidepressants
Low-dose for pain modulation.
Show evidence (1 reference)
PMID:24935275 SUPPORT Human Clinical
"with similar treatment effects for both tricyclic antidepressants and selective serotonin reuptake inhibitors."
Meta-analysis of RCTs demonstrating that tricyclic antidepressants are an effective treatment for IBS.
SSRIs
For patients with comorbid anxiety/depression.
Show evidence (1 reference)
PMID:24935275 SUPPORT Human Clinical
"with similar treatment effects for both tricyclic antidepressants and selective serotonin reuptake inhibitors."
The same meta-analysis found selective serotonin reuptake inhibitors to have treatment effects comparable to tricyclic antidepressants in IBS.
Probiotics
May help some patients.
Show evidence (1 reference)
PMID:19091823 SUPPORT Human Clinical
"Probiotics appear to be efficacious in IBS, but the magnitude of benefit and the most effective species and strain are uncertain."
Systematic review of RCTs indicating probiotics are efficacious in IBS, while the optimal strain remains uncertain.
Antihistamines
H1 receptor antagonists for mast cell-mediated symptoms. Mast cell mediators including histamine contribute to visceral hypersensitivity and abdominal pain in IBS. Antihistamines are emerging as a barrier-restoration strategy targeting mast cell dysfunction.
Show evidence (1 reference)
PMID:42413530 SUPPORT Other
"novel therapeutics, including antihistamines, mast cell stabilisers, protease inhibitors, secretagogues, and guanylate cyclase C agonists"
Recent review identifies antihistamines as novel therapeutic agents for barrier restoration in disorders of gut-brain interaction.
Mast Cell Stabilizers
Agents that prevent mast cell degranulation and release of mediators (histamine, tryptase) that excite visceral sensory neurons. Elevated mast cell activation is a key driver of symptoms in a subset of IBS patients, making stabilizers a rational barrier-protective approach.
Show evidence (1 reference)
PMID:42413530 SUPPORT Other
"novel therapeutics, including antihistamines, mast cell stabilisers, protease inhibitors, secretagogues, and guanylate cyclase C agonists"
Recent review identifies mast cell stabilizers as novel therapeutic agents for barrier restoration in disorders of gut-brain interaction.
Cognitive Behavioral Therapy
Effective for gut-brain axis modulation.
Show evidence (1 reference)
PMID:24935275 SUPPORT Human Clinical
"Cognitive behavioral therapy, hypnotherapy, multicomponent psychological therapy, and dynamic psychotherapy were all beneficial."
Meta-analysis evidence that cognitive behavioral therapy is a beneficial psychological therapy for IBS, consistent with gut-brain modulation.
🌍

Environmental Factors

5
Psychological Stress
psychological stress XCO:0001265 Experimental Conditions Ontology (XCO) Relation: this environmental factor is this exposure This environmental factor is psychological stress, annotated with stress (XCO:0001265). XCO:0001265 is an exposure from the Experimental Conditions Ontology.
Major trigger for symptoms
Show evidence (1 reference)
PMID:25339801 SUPPORT Other
"cause symptom flare-ups or exaggeration in IBS"
Review of the stress-IBS relationship, attributing flares to stress-induced neuro-endocrine-immune changes acting on the gut-brain axis. OTHER because the quoted sentence is a mechanistic synthesis rather than a reported measurement.
Dietary Triggers
FODMAPs, gluten in some patients
Show evidence (1 reference)
PMID:28846594 SUPPORT Human Clinical
"the patients receiving a low-FODMAP diet experienced a statistically significant pain and bloating reduction compared with those receiving a traditional diet"
Meta-analysis of randomized trials supporting the FODMAP half of this annotation. PARTIAL: the gluten claim is not evidenced here, and the review notes it remains undemonstrated whether a low-FODMAP diet beats conventional IBS diets long term.
Mechanism Target:
EXACERBATES Abdominal Pain — Fermentable oligo-, di-, monosaccharides and polyols in the diet contribute to abdominal pain in IBS.
Show evidence (1 reference)
PMID:28846594 SUPPORT INDIRECT Human Clinical
"the patients receiving a low-FODMAP diet experienced a statistically significant pain and bloating reduction compared with those receiving a traditional diet"
The trial measures symptom improvement on FODMAP restriction rather than provocation, so the exacerbating role of dietary FODMAPs follows by inference from the removal design. The edge also jumps the visceral-hypersensitivity and dysmotility nodes that mediate it. Scoped to FODMAPs; the gluten half of this annotation is not evidenced here.
EXACERBATES Bloating — Fermentable oligo-, di-, monosaccharides and polyols in the diet contribute to bloating in IBS.
Show evidence (1 reference)
PMID:28846594 SUPPORT INDIRECT Human Clinical
"the patients receiving a low-FODMAP diet experienced a statistically significant pain and bloating reduction compared with those receiving a traditional diet"
The same meta-analysis reports bloating reduction alongside pain reduction on a low-FODMAP diet, so the claim rests on the same removal design and the same omitted intermediate nodes as the pain edge.
Gastroenteritis
Post-infectious IBS
Show evidence (1 reference)
PMID:22024145 SUPPORT Human Clinical
"The odds of developing IBS are increased after acute gastrointestinal infection"
Meta-analysis of ten studies giving a pooled OR of 6.03 for IBS after acute gastroenteritis, the post-infectious mechanism this annotation names.
Antibiotics
Associated with increased IBS risk (IRR 1.3), especially after gastrointestinal infection; microbiome disruption is the proposed mechanism
Show evidence (1 reference)
PMID:41860116 SUPPORT Human Clinical
"Antibiotic use is associated with increased risk of developing IBS, especially after gastrointestinal infections"
Meta-analysis of 31 studies (422,350 patients), IRR 1.3. PARTIAL, and the note was rewritten: the meta-analysis measures risk, not the microbiome mechanism the note previously asserted, and its authors flag heterogeneity above 90% as limiting the result.
Early Life Stress
psychological stress XCO:0001265 Experimental Conditions Ontology (XCO) Relation: this environmental factor is this exposure This environmental factor is psychological stress, annotated with stress (XCO:0001265). XCO:0001265 is an exposure from the Experimental Conditions Ontology.
May predispose to IBS
Show evidence (2 references)
PMID:38783444 SUPPORT Human Clinical
"The pooled odds ratio, indicating the association between childhood sexual abuse and irritable bowel syndrome, was 1.87"
Systematic review of 7 studies (3,156 subjects) for one specific early-life exposure.
PMID:35086857 SUPPORT Human Clinical
"found the association between ACEs and IBS to be uncertain given the considerable heterogeneity"
Deliberately paired with the citation above: across 15 studies and 272,686 participants the broader adverse-childhood-experience association is uncertain, with I2 = 93.58% and significant publication bias. This is why the annotation says 'may predispose' rather than asserting the link.
📊

Prevalence

1
United States
Point Prevalence 17500.0 per 100,000 (10000.0–25000.0) >1 in 1,000
Review-reported US prevalence range of 10-25%; midpoint recorded as the point estimate.
Show evidence (1 reference)
PMID:37048642 SUPPORT Human Clinical
"It has a prevalence of 10 to 25% in the United States and has a high disease burden, as evidenced by reduced quality of life, decreased work productivity and increased healthcare utilization and costs."
Gives the US population prevalence range for IBS.
📊

Related Datasets

4
Gene expression analysis of rectal mucosa in chronic irritable bowel syndrome (IBS) compared to healthy volunteers (HV) geo:GSE36701
Microarray analysis of rectal mucosal biopsies from patients with chronic IBS and healthy volunteers to identify differentially expressed genes related to intestinal barrier function and visceral hypersensitivity.
human MICROARRAY Affymetrix Human Genome U133 Plus 2.0 Array
rectal mucosa biopsy UBERON:0001052 Uberon multi-species anatomy ontology (UBERON) Relation: this dataset samples this sample type This dataset samples rectal mucosa biopsy, annotated with rectum (UBERON:0001052). UBERON:0001052 is a sample type from the Uberon multi-species anatomy ontology.
Conditions: chronic IBS healthy controls
Widely used IBS dataset for biomarker discovery. Key targets identified include EGFR, VEGFA, BCL2L1, CASP9, MMP9, MAPK14.
Expression data from healthy volunteers and IBS patients geo:GSE14841
Microarray profiling of jejunal mucosal biopsies from 5 IBS-D patients and 4 healthy volunteers as a pilot study to characterize gene expression patterns in diarrhea-predominant IBS.
human MICROARRAY n=9
jejunal mucosa biopsy UBERON:0002115 Uberon multi-species anatomy ontology (UBERON) Relation: this dataset samples this sample type This dataset samples jejunal mucosa biopsy, annotated with jejunum (UBERON:0002115). UBERON:0002115 is a sample type from the Uberon multi-species anatomy ontology.
Conditions: IBS-D (diarrhea-predominant) healthy controls
Smaller pilot dataset often combined with GSE36701 for meta-analysis. Studies have identified 1257 differentially expressed genes between IBS-D and controls.
IBS gut microbiota and metabolome profiling bioproject:PRJNA566284
16S rRNA gene sequencing of fecal samples from IBS patients and healthy controls at Beijing Friendship Hospital to investigate gut microbiota composition and identify potential biomarkers.
human gut metagenome WGS n=29
fecal sample UBERON:0001988 Uberon multi-species anatomy ontology (UBERON) Relation: this dataset samples this sample type This dataset samples fecal sample, annotated with feces (UBERON:0001988). UBERON:0001988 is a sample type from the Uberon multi-species anatomy ontology.
Conditions: IBS patients healthy controls
Combined with metabolomics data to investigate mechanisms underlying IBS through microbiologic and metabolomic profiling. This is 16S rRNA amplicon sequencing, not shotgun metagenomics; data_type is recorded as WGS because DatasetTypeEnum has no amplicon-sequencing value.
American Gut Project mgnify:MGYS00000596
16S rRNA V4 region sequencing from the American Gut Project citizen science initiative. Contains 942 IBS subjects (IBS-D, IBS-C, IBS-U subtypes) matched with 942 non-IBS controls by age, gender, BMI, geography, and dietary patterns.
human gut metagenome WGS n=1884
fecal sample UBERON:0001988 Uberon multi-species anatomy ontology (UBERON) Relation: this dataset samples this sample type This dataset samples fecal sample, annotated with feces (UBERON:0001988). UBERON:0001988 is a sample type from the Uberon multi-species anatomy ontology.
Conditions: IBS-D (diarrhea-predominant) IBS-C (constipation-predominant) IBS-U (unclassified) healthy controls
PMID:36573834
Large-scale microbiome study showing IBS-D and IBS-U have reduced bacterial diversity (Shannon index). Identifies associations between gut microbiota and depression in IBS subtypes. Bifidobacterium and SCFA pathways reduced in IBS with depression
{ }

Source YAML

click to show 
name: Irritable Bowel Syndrome
creation_date: '2025-12-18T17:01:35Z'
description: >-
  Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder
  defined by recurrent abdominal pain associated with altered bowel habits in the
  absence of structural disease. Its pathophysiology reflects disordered gut-brain
  axis signaling, including visceral hypersensitivity, gut dysmotility, low-grade
  mucosal immune activation with mast cell involvement, intestinal barrier
  dysfunction, and microbiome dysbiosis. Patients are classified by predominant
  stool pattern (diarrhea-predominant, constipation-predominant, or mixed), and
  management targets symptoms through diet, the microbiome, and gut-brain modulation.
category: Complex
parents:
- Gastrointestinal Disease
disease_term:
  preferred_term: irritable bowel syndrome
  term:
    id: MONDO:0005052
    label: irritable bowel syndrome
prevalence:
- population: United States
  measure_type: POINT_PREVALENCE
  prevalence_class: ABOVE_1_IN_1000
  rate_low: 10000.0
  rate_high: 25000.0
  rate_per_100000: 17500.0
  notes: Review-reported US prevalence range of 10-25%; midpoint recorded as the point estimate.
  evidence:
  - reference: PMID:37048642
    reference_title: "Irritable Bowel Syndrome and the Gut Microbiome: A Comprehensive Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It has a prevalence of 10 to 25% in the United States and has a high
      disease burden, as evidenced by reduced quality of life, decreased work productivity
      and increased healthcare utilization and costs."
    explanation: Gives the US population prevalence range for IBS.
pathophysiology:
- name: Visceral Hypersensitivity
  description: >
    Enhanced perception of normal gut sensations leads to pain and
    discomfort. Lowered pain thresholds in response to balloon
    distension. Central sensitization contributes.
  biological_processes:
  - preferred_term: Pain Perception
    term:
      id: GO:0048265
      label: response to pain
  evidence:
  - reference: PMID:18252749
    reference_title: "Increased capsaicin receptor TRPV1-expressing sensory fibres in irritable bowel syndrome and their correlation with abdominal pain."
    supports: SUPPORT
    snippet: "A significant 3.5-fold increase in median numbers of TRPV1-immunoreactive
      fibres was found in biopsies from IBS patients compared with controls (p<0.0001)."
    explanation: TRPV1-expressing sensory nerve fibers are significantly
      increased in IBS, providing a molecular basis for visceral
      hypersensitivity.
  - reference: PMID:18252749
    reference_title: "Increased capsaicin receptor TRPV1-expressing sensory fibres in irritable bowel syndrome and their correlation with abdominal pain."
    supports: SUPPORT
    snippet: "In multivariate regression analysis, only TRPV1-immuno-reactive fibres
      (p = 0.005) and mast cells (p = 0.008) were significantly related to the abdominal
      pain score."
    explanation: TRPV1 nerve fiber density directly correlates with abdominal
      pain severity in IBS patients.
  - reference: PMID:17241857
    reference_title: "Mast cell-dependent excitation of visceral-nociceptive sensory neurons in irritable bowel syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Mediators from IBS patients, but not controls, markedly enhanced the
      firing of mesenteric nerves (14.7 +/- 3.2 imp/sec vs 2.8 +/- 1.5 imp/sec; P
      < .05) and stimulated mobilization of Ca(2+) in dorsal root ganglia neurons
      (29% +/- 4% vs 11% +/- 4%; P < .05)."
    explanation: Mucosal mediators from IBS patients directly excite visceral
      sensory neurons, demonstrating a mechanism for visceral hypersensitivity.
  - reference: PMID:17241857
    reference_title: "Mast cell-dependent excitation of visceral-nociceptive sensory neurons in irritable bowel syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "On average, 64% of dorsal root ganglia responsive to mediators were
      capsaicin-sensitive, known to mediate nociception."
    explanation: The majority of sensory neurons activated by IBS mucosal
      mediators are nociceptive, explaining the pain phenotype.
- name: Gut Dysmotility
  description: >
    Altered intestinal motility patterns with either accelerated
    (diarrhea-predominant) or delayed (constipation-predominant)
    transit. Abnormal colonic contractions.
  cell_types:
  - preferred_term: enterochromaffin cell
    term:
      id: CL:0000577
      label: type EC enteroendocrine cell
  biological_processes:
  - preferred_term: Gut Motility
    term:
      id: GO:0030432
      label: peristalsis
  evidence:
  - reference: PMID:15100164
    reference_title: "Role of serotonin in the pathophysiology of the irritable bowel syndrome."
    supports: SUPPORT
    snippet: "5-HT release from enterochromaffin (EC) cells initiates peristaltic,
      secretory, vasodilatory, vagal and nociceptive reflexes."
    explanation: Serotonin from enterochromaffin cells is a key regulator of
      intestinal motility and peristaltic reflexes.
  - reference: PMID:15100164
    reference_title: "Role of serotonin in the pathophysiology of the irritable bowel syndrome."
    supports: SUPPORT
    snippet: "5-HT directly and indirectly affects intestinal motor and secretory
      function and abnormalities may lead to either constipation or diarrhea."
    explanation: Dysregulated serotonin signaling can account for both IBS-D and
      IBS-C subtypes through effects on motility.
- name: Gut-Brain Axis Dysfunction
  description: >
    Bidirectional communication between gut and brain is disrupted.
    Stress and psychological factors modulate gut function through
    autonomic and neuroendocrine pathways.
  biological_processes:
  - preferred_term: Nervous System Process
    term:
      id: GO:0050877
      label: nervous system process
  evidence:
  - reference: PMID:37048642
    reference_title: "Irritable Bowel Syndrome and the Gut Microbiome: A Comprehensive Review."
    supports: SUPPORT
    snippet: "Although the pathophysiology of IBS has not been fully elucidated, it
      involves dysregulation of communication between the brain and gut (brain-gut
      axis) which is associated with alterations in intestinal motility, gut permeability,
      visceral hypersensitivity and gut microbiota composition."
    explanation: The gut-brain axis is a central organizing principle in IBS
      pathophysiology, integrating multiple dysfunctional mechanisms.
  - reference: PMID:15100164
    reference_title: "Role of serotonin in the pathophysiology of the irritable bowel syndrome."
    supports: SUPPORT
    snippet: "Ongoing, bidirectional brain-gut interactions involving 5-HT pathways
      occur that significantly influence the effector systems."
    explanation: Serotonin pathways mediate bidirectional brain-gut
      communication in IBS.
- name: Intestinal Barrier Dysfunction
  description: >
    Increased intestinal permeability (leaky gut) allows translocation
    of luminal antigens, triggering low-grade immune activation. Mucosal
    disruption encompasses alterations in epithelial and mucus layers.
    Barrier restoration via dietary, microbial, and pharmacological
    interventions is emerging as a therapeutic strategy.
  evidence:
  - reference: PMID:17593135
    reference_title: "Intestinal permeability and irritable bowel syndrome."
    supports: SUPPORT
    snippet: "While a subgroup of patients with IBS appears to have evidence of increased
      intestinal permeability, improvements in the methods and validation are key
      to further research in this field in order to better understand intestinal barrier
      functions in IBS."
    explanation: A subset of IBS patients demonstrate measurable increases in
      intestinal permeability, though the exact prevalence varies by
      methodology.
  - reference: PMID:19595511
    reference_title: "Intestinal membrane permeability and hypersensitivity in the irritable bowel syndrome."
    supports: SUPPORT
    snippet: "Approximately 39% of diarrhea-predominant IBS patients had increased
      intestinal membrane permeability as measured by the lactulose/mannitol ratio."
    explanation: Nearly 40% of IBS-D patients show objective evidence of barrier
      dysfunction using validated permeability testing.
  - reference: PMID:19595511
    reference_title: "Intestinal membrane permeability and hypersensitivity in the irritable bowel syndrome."
    supports: SUPPORT
    snippet: "A subset of D-IBS patients had increased intestinal membrane permeability
      that was associated with an increased FBDSI score and increased hypersensitivity
      to visceral and thermal nociceptive pain stimuli."
    explanation: Barrier dysfunction in IBS-D correlates with more severe
      symptoms and heightened visceral sensitivity, linking permeability to
      clinical phenotype.
  - reference: PMID:42413530
    reference_title: "Barrier restoration as a therapeutic strategy for disorders of gut-brain interaction."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "short-chain fatty acids, amino acids (glutamine and tryptophan), and
      targeted probiotics can enhance tight junction integrity and mucin secretion"
    explanation: Specific dietary metabolites and probiotics enhance intestinal
      barrier integrity, supporting barrier-restoration as a therapeutic
      strategy in IBS.
  - reference: PMID:42413530
    reference_title: "Barrier restoration as a therapeutic strategy for disorders of gut-brain interaction."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "psychological stress, low-fibre diets, and high-fat diets disrupt these
      pathways"
    explanation: Stress and specific dietary patterns disrupt tight junction and
      mucus layer integrity, identifying modifiable environmental contributors
      to barrier dysfunction in IBS.
- name: Immune Activation and Mast Cell Degranulation
  description: >
    Low-grade mucosal immune activation with increased mast cell density
    and degranulation near enteric nerves. Mast cell mediators including
    histamine and tryptase excite visceral sensory neurons, contributing
    to pain and hypersensitivity.
  cell_types:
  - preferred_term: mast cell
    term:
      id: CL:0000097
      label: mast cell
  biological_processes:
  - preferred_term: Mast Cell Activation
    term:
      id: GO:0045576
      label: mast cell activation
  evidence:
  - reference: PMID:17241857
    reference_title: "Mast cell-dependent excitation of visceral-nociceptive sensory neurons in irritable bowel syndrome."
    supports: SUPPORT
    snippet: "IBS-dependent nerve firing and Ca(2+) mobilization were correlated with
      the area of the colonic lamina propria occupied by mast cells (r = 0.74; P <
      .01, and r = 0.78; P < .01, respectively)."
    explanation: Mast cell density directly correlates with sensory neuron
      activation in IBS, establishing a quantitative relationship.
  - reference: PMID:17241857
    reference_title: "Mast cell-dependent excitation of visceral-nociceptive sensory neurons in irritable bowel syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Mucosal mast cell mediators from IBS patients excite rat nociceptive
      visceral sensory nerves. These results provide new insights into the mechanism
      underlying visceral hypersensitivity in IBS."
    explanation: Mast cell mediators from IBS patients directly activate
      nociceptive neurons, providing a mechanistic link to pain.
  - reference: PMID:18252749
    reference_title: "Increased capsaicin receptor TRPV1-expressing sensory fibres in irritable bowel syndrome and their correlation with abdominal pain."
    supports: SUPPORT
    snippet: "Substance P-immunoreactive fibres (p = 0.01), total nerve fibres (PGP9.5)
      (p = 0.002), mast cells (c-kit) (p = 0.02) and lymphocytes (CD3) (p = 0.03)
      were also significantly increased in the IBS group."
    explanation: Both mast cells and immune cells are increased in IBS mucosa,
      indicating low-grade immune activation.
- name: Microbiome Dysbiosis
  description: >
    Altered composition and function of gut microbiota may contribute
    to symptoms. Post-infectious IBS follows gastroenteritis in
    some patients. Genus-level composition is modifiable by dietary
    fermentable substrate: adding high-amylose resistant starch to a
    low-FODMAP diet shifts composition and enriches the resistant-starch
    degrader Ruminococcus E. Whether such a shift moves the community
    toward a healthy-donor reference is untested, as the trials reporting
    it carry no healthy-control arm.
  biological_processes:
  - preferred_term: Host-Microbiome Interaction
    term:
      id: GO:0044003
      label: symbiont-mediated perturbation of host process
  evidence:
  - reference: PMID:37048642
    reference_title: "Irritable Bowel Syndrome and the Gut Microbiome: A Comprehensive Review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Although the pathophysiology of IBS has not been fully elucidated, it
      involves dysregulation of communication between the brain and gut (brain-gut
      axis) which is associated with alterations in intestinal motility, gut permeability,
      visceral hypersensitivity and gut microbiota composition."
    explanation: Names altered gut microbiota composition as a component of IBS
      pathophysiology, which is the claim of this node.
  - reference: PPR:PPR1298203
    reference_title: "Dietary fibre blend improves gut health in patients with Irritable
      Bowel Syndrome following a low FODMAP diet: a randomised, double-blind control
      trial"
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "A specific mix of fibres can increase fibre intake, improve gut microbiota and gastrointestinal-specific anxiety without impacting sleep and symptoms of IBS patients on a low FODMAP diet as compared with placebo, despite no changes found in faecal and blood biomarkers."
    explanation: >-
      Small randomised trial (n=26, 13 per arm; non-peer-reviewed preprint) showing
      that genus-level community composition in IBS shifts measurably when a
      high-amylose resistant starch blend is added to a low-FODMAP diet. Indirect
      support for this node: it demonstrates the community is modifiable by dietary
      substrate rather than measuring dysbiosis against a healthy reference, for
      which the trial has no control arm.
phenotypes:
- name: Abdominal Pain
  category: Gastrointestinal
  frequency: VERY_FREQUENT
  diagnostic: true
  notes: Related to defecation
  phenotype_term:
    preferred_term: Abdominal Pain
    term:
      id: HP:0002027
      label: Abdominal pain
  evidence:
  - reference: PMID:18252749
    reference_title: "Increased capsaicin receptor TRPV1-expressing sensory fibres in irritable bowel syndrome and their correlation with abdominal pain."
    supports: SUPPORT
    snippet: "Increased TRPV1 nerve fibres are observed in IBS, together with a low-grade
      inflammatory response. The increased TRPV1 nerve fibres may contribute to visceral
      hypersensitivity and pain in IBS, and provide a novel therapeutic target."
    explanation: TRPV1-expressing nerve fibers are increased in IBS and directly
      linked to abdominal pain severity.
  - reference: PMID:17241857
    reference_title: "Mast cell-dependent excitation of visceral-nociceptive sensory neurons in irritable bowel syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "IBS-dependent excitation of dorsal root ganglia was inhibited by histamine
      H(1) receptor blockade and serine protease inactivation (inhibition of 51.7%;
      P < .05 and 74.5%; P < .05; respectively)."
    explanation: Mast cell mediators, particularly histamine and proteases,
      directly excite nociceptive neurons to produce abdominal pain in IBS.
- name: Altered Bowel Habits
  category: Gastrointestinal
  frequency: VERY_FREQUENT
  diagnostic: true
  phenotype_term:
    preferred_term: Altered bowel habits
    term:
      id: HP:0030895
      label: Abnormal gastrointestinal motility
  evidence:
  - reference: PMID:15100164
    reference_title: "Role of serotonin in the pathophysiology of the irritable bowel syndrome."
    supports: SUPPORT
    snippet: "5-HT directly and indirectly affects intestinal motor and secretory
      function and abnormalities may lead to either constipation or diarrhea."
    explanation: Dysregulated serotonergic control of gut motility underlies the
      alternating and altered bowel habits characteristic of IBS.
- name: Bloating
  category: Gastrointestinal
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Abdominal Distention
    term:
      id: HP:0003270
      label: Abdominal distention
  evidence:
  - reference: PMID:24076059
    reference_title: "A diet low in FODMAPs reduces symptoms of irritable bowel syndrome."
    supports: SUPPORT
    snippet: "Bloating, pain, and passage of wind also were reduced while IBS
      patients were on the low-FODMAP diet."
    explanation: Bloating is a cardinal IBS symptom, here shown to be modifiable
      by reducing fermentable carbohydrate intake.
- name: Constipation
  category: Gastrointestinal
  frequency: FREQUENT
  notes: IBS-C subtype
  phenotype_term:
    preferred_term: Constipation
    term:
      id: HP:0002019
      label: Constipation
  evidence:
  - reference: PMID:22986437
    reference_title: "Linaclotide for irritable bowel syndrome with constipation: a 26-week,
      randomized, double-blind, placebo-controlled trial to evaluate efficacy and safety."
    supports: SUPPORT
    snippet: "The objective of this trial was to determine the efficacy and safety of
      linaclotide treatment in patients with irritable bowel syndrome with
      constipation (IBS-C) over 26 weeks."
    explanation: Constipation defines the IBS-C subtype and is the target symptom
      for the guanylate cyclase-C agonist linaclotide.
- name: Diarrhea
  category: Gastrointestinal
  frequency: FREQUENT
  notes: IBS-D subtype
  phenotype_term:
    preferred_term: Diarrhea
    term:
      id: HP:0002014
      label: Diarrhea
  evidence:
  - reference: PMID:19595511
    reference_title: "Intestinal membrane permeability and hypersensitivity in the irritable bowel syndrome."
    supports: SUPPORT
    snippet: "Approximately 39% of diarrhea-predominant IBS patients had increased
      intestinal membrane permeability as measured by the lactulose/mannitol ratio."
    explanation: Increased intestinal permeability is present in a substantial
      proportion of IBS-D patients and may contribute to diarrheal symptoms.
  - reference: PMID:15100164
    reference_title: "Role of serotonin in the pathophysiology of the irritable bowel syndrome."
    supports: SUPPORT
    snippet: "5-HT directly and indirectly affects intestinal motor and secretory
      function and abnormalities may lead to either constipation or diarrhea."
    explanation: Dysregulated serotonin signaling affects secretion and
      motility, contributing to diarrhea in IBS-D.
- name: Fatigue
  category: Systemic
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Fatigue
    term:
      id: HP:0012378
      label: Fatigue
genetic:
- name: HTR3E
  gene_term:
    preferred_term: HTR3E
    term:
      id: hgnc:24005
      label: HTR3E
  association: Risk Factor
  notes: Serotonin receptor
- name: SCN5A
  gene_term:
    preferred_term: SCN5A
    term:
      id: hgnc:10593
      label: SCN5A
  association: Risk Factor
  notes: Sodium channel
environmental:
- name: Psychological Stress
  exposure_term:
    preferred_term: psychological stress
    term:
      id: XCO:0001265
      label: stress
  notes: Major trigger for symptoms
  evidence:
  - reference: PMID:25339801
    reference_title: "Impact of psychological stress on irritable bowel syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "cause symptom flare-ups or exaggeration in IBS"
    explanation: "Review of the stress-IBS relationship, attributing flares to stress-induced neuro-endocrine-immune changes acting on the gut-brain axis. OTHER because the quoted sentence is a mechanistic synthesis rather than a reported measurement."
- name: Dietary Triggers
  notes: FODMAPs, gluten in some patients
  evidence:
  - reference: PMID:28846594
    reference_title: "Low-FODMAP Diet Improves Irritable Bowel Syndrome Symptoms: A Meta-Analysis"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the patients receiving a low-FODMAP diet experienced a statistically significant pain and bloating reduction compared with those receiving a traditional diet"
    explanation: "Meta-analysis of randomized trials supporting the FODMAP half of this annotation. PARTIAL: the gluten claim is not evidenced here, and the review notes it remains undemonstrated whether a low-FODMAP diet beats conventional IBS diets long term."
  influences_mechanisms:
  - target: Abdominal Pain
    environmental_effect: EXACERBATES
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Fermentable oligo-, di-, monosaccharides and polyols in the diet contribute to abdominal pain in IBS.
    evidence:
    - reference: PMID:28846594
      reference_title: "Low-FODMAP Diet Improves Irritable Bowel Syndrome Symptoms: A Meta-Analysis"
      supports: SUPPORT
      directness: INDIRECT
      evidence_source: HUMAN_CLINICAL
      snippet: the patients receiving a low-FODMAP diet experienced a statistically significant pain and bloating reduction compared with those receiving a traditional diet
      explanation: The trial measures symptom improvement on FODMAP restriction rather than provocation, so the exacerbating role of dietary FODMAPs follows by inference from the removal design. The edge also jumps the visceral-hypersensitivity and dysmotility nodes that mediate it. Scoped to FODMAPs; the gluten half of this annotation is not evidenced here.
  - target: Bloating
    environmental_effect: EXACERBATES
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Fermentable oligo-, di-, monosaccharides and polyols in the diet contribute to bloating in IBS.
    evidence:
    - reference: PMID:28846594
      reference_title: "Low-FODMAP Diet Improves Irritable Bowel Syndrome Symptoms: A Meta-Analysis"
      supports: SUPPORT
      directness: INDIRECT
      evidence_source: HUMAN_CLINICAL
      snippet: the patients receiving a low-FODMAP diet experienced a statistically significant pain and bloating reduction compared with those receiving a traditional diet
      explanation: The same meta-analysis reports bloating reduction alongside pain reduction on a low-FODMAP diet, so the claim rests on the same removal design and the same omitted intermediate nodes as the pain edge.
- name: Gastroenteritis
  notes: Post-infectious IBS
  evidence:
  - reference: PMID:22024145
    reference_title: "The incidence and risk factors of post-infectious irritable bowel syndrome: a meta-analysis"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The odds of developing IBS are increased after acute gastrointestinal infection"
    explanation: "Meta-analysis of ten studies giving a pooled OR of 6.03 for IBS after acute gastroenteritis, the post-infectious mechanism this annotation names."
- name: Antibiotics
  notes: Associated with increased IBS risk (IRR 1.3), especially after
    gastrointestinal infection; microbiome disruption is the proposed mechanism
  evidence:
  - reference: PMID:41860116
    reference_title: "Antibiotic Use During Gastrointestinal Infections Increases the Risk of Developing Irritable Bowel Syndrome: A Systematic Review and Meta-Analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Antibiotic use is associated with increased risk of developing IBS, especially after gastrointestinal infections"
    explanation: "Meta-analysis of 31 studies (422,350 patients), IRR 1.3. PARTIAL, and the note was rewritten: the meta-analysis measures risk, not the microbiome mechanism the note previously asserted, and its authors flag heterogeneity above 90% as limiting the result."
- name: Early Life Stress
  exposure_term:
    preferred_term: psychological stress
    term:
      id: XCO:0001265
      label: stress
  notes: May predispose to IBS
  evidence:
  - reference: PMID:38783444
    reference_title: "Evaluating the association of childhood sexual abuse with the development of irritable bowel syndrome later in life: A systematic review"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The pooled odds ratio, indicating the association between childhood sexual abuse and irritable bowel syndrome, was 1.87"
    explanation: "Systematic review of 7 studies (3,156 subjects) for one specific early-life exposure."
  - reference: PMID:35086857
    reference_title: "Meta-analysis and systematic review of the association between adverse childhood events and irritable bowel syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "found the association between ACEs and IBS to be uncertain given the considerable heterogeneity"
    explanation: "Deliberately paired with the citation above: across 15 studies and 272,686 participants the broader adverse-childhood-experience association is uncertain, with I2 = 93.58% and significant publication bias. This is why the annotation says 'may predispose' rather than asserting the link."
treatments:
- name: Dietary Modification
  description: Low FODMAP diet effective in many patients.
  evidence:
  - reference: PMID:24076059
    reference_title: "A diet low in FODMAPs reduces symptoms of irritable bowel syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In a controlled, cross-over study of patients with IBS, a diet low
      in FODMAPs effectively reduced functional gastrointestinal symptoms."
    explanation: Randomized cross-over trial evidence that a low-FODMAP diet reduces
      IBS symptoms, supporting it as a first-line dietary intervention.
- name: Soluble Fiber (Psyllium)
  description: >-
    Supplementation with soluble fiber (psyllium/ispaghula husk) as a first-line
    treatment to improve global symptoms and abdominal pain in IBS. Unlike
    insoluble fiber (bran), soluble psyllium provides adequate symptom relief and
    is recommended by guidelines as a bulking agent for IBS.
  treatment_term:
    preferred_term: dietary intervention
    term:
      id: NCIT:C15447
      label: Dietary Intervention
  evidence:
  - reference: PMID:19713235
    reference_title: "Soluble or insoluble fibre in irritable bowel syndrome in primary
      care? Randomised placebo controlled trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Psyllium offers benefits in patients with irritable bowel syndrome
      in primary care."
    explanation: Primary-care randomised controlled trial showing that soluble fiber
      (psyllium), unlike insoluble bran, gives adequate symptom relief in adult IBS.
  - reference: PPR:PPR1275071
    reference_title: "Randomized Placebo-Controlled Trial of Psyllium Fiber in Functional
      Abdominal Pain Disorders in Children"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A 12-week trial of psyllium fiber improves pain in most and gives sustained
      relief in three-fourths of children with FAP-NOS and IBS."
    explanation: >-
      Pediatric randomised placebo-controlled trial (non-peer-reviewed preprint;
      corroborating the adult primary-care RCT) reporting that psyllium fiber
      improves and sustains pain relief in children with IBS and functional
      abdominal pain.
- name: High-Amylose Resistant Starch and Psyllium Blend
  description: >-
    Supplementation of an established low-FODMAP diet with a blend of high-amylose
    maize resistant starch (HAMS) and psyllium husk, as an adjunct aimed at the
    microbial cost of FODMAP restriction rather than at symptom control. Distinct
    from psyllium monotherapy: the single trial reporting it used a
    psyllium-matched placebo, so the effects below are the incremental effect of
    the resistant-starch component on a psyllium background, not an effect of
    psyllium. Investigational — one small unreplicated preprint trial, with no
    guideline standing.
  treatment_term:
    preferred_term: dietary intervention
    term:
      id: NCIT:C15447
      label: Dietary Intervention
  target_mechanisms:
  - target: Microbiome Dysbiosis
    treatment_effect: MODULATES
    description: >-
      The resistant-starch component supplies fermentable substrate lost under
      FODMAP restriction, shifting genus-level composition and enriching the
      primary resistant-starch degrader Ruminococcus E. Recorded as MODULATES
      rather than RESTORES because the trial reports compositional change against
      a psyllium-matched placebo, not movement toward a healthy-donor reference.
    evidence:
    - reference: PPR:PPR1298203
      reference_title: "Dietary fibre blend improves gut health in patients with
        Irritable Bowel Syndrome following a low FODMAP diet: a randomised,
        double-blind control trial"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "This relative abundance was greater than that of the placebo group at T2"
      explanation: >-
        Reports the compositional shift this link asserts, in the arm receiving
        the resistant-starch blend.
  evidence:
  - reference: PPR:PPR1298203
    reference_title: "Dietary fibre blend improves gut health in patients with Irritable
      Bowel Syndrome following a low FODMAP diet: a randomised, double-blind control
      trial"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "ur gut® improved GI-specific anxiety (P = 0.01) and sexual subscale
      of QOL (P = 0.018)."
    explanation: >-
      Randomised double-blind trial (n=26, 13 per arm; non-peer-reviewed preprint)
      reporting improved GI-specific anxiety and the sexual subscale of quality of
      life in the blend arm. The comparator contained an identical psyllium dose,
      so this is the incremental effect of the resistant-starch component.
  - reference: PPR:PPR1298203
    reference_title: "Dietary fibre blend improves gut health in patients with Irritable
      Bowel Syndrome following a low FODMAP diet: a randomised, double-blind control
      trial"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "observed intervention effects were not due to psyllium husk, the placebo incorporated"
    explanation: >-
      Establishes that psyllium was controlled out by design, which is why this is
      curated as a separate treatment rather than as further support for the
      psyllium entry.
  notes: >-
    Trial registration and full composition (56 g dietary fibre per 100 g, of which
    36 g is resistant starch) are in the cited preprint. Symptom severity, the
    trial's primary outcome, did not differ between arms; faecal and blood
    biomarkers were unchanged. Treat the microbiota and anxiety findings as
    secondary outcomes of a 13-vs-13 study pending peer review and replication.
- name: Antispasmodics
  description: Dicyclomine, hyoscyamine for pain and cramping.
  evidence:
  - reference: PMID:40307155
    reference_title: "Pharmacologic treatment of irritable bowel syndrome. Position statement of the Asociación Mexicana de Gastroenterología, 2024."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Antispasmodics (alone or combined) are used as first-line therapy for pain management, whereas antidiarrheals, such as loperamide, are used for reducing diarrhea in diarrhea-predominant IBS (IBS-D) and laxatives are used for constipation in constipation-predominant IBS (IBS-C)."
    explanation: The guideline positions antispasmodics, alone or combined, as first-line therapy for pain management in irritable bowel syndrome.
- name: Loperamide
  description: For diarrhea-predominant IBS.
  evidence:
  - reference: PMID:40307155
    reference_title: "Pharmacologic treatment of irritable bowel syndrome. Position statement of the Asociación Mexicana de Gastroenterología, 2024."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Antispasmodics (alone or combined) are used as first-line therapy for pain management, whereas antidiarrheals, such as loperamide, are used for reducing diarrhea in diarrhea-predominant IBS (IBS-D) and laxatives are used for constipation in constipation-predominant IBS (IBS-C)."
    explanation: The guideline positions antidiarrheals such as loperamide as therapy for reducing diarrhea in diarrhea-predominant IBS.
- name: Linaclotide
  description: Guanylate cyclase agonist for IBS-C.
  evidence:
  - reference: PMID:22986437
    reference_title: "Linaclotide for irritable bowel syndrome with constipation: a 26-week,
      randomized, double-blind, placebo-controlled trial to evaluate efficacy and safety."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Linaclotide 290 μg once daily significantly improved abdominal and
      bowel symptoms associated with IBS-C over 26 weeks of treatment."
    explanation: Phase 3 RCT demonstrating linaclotide efficacy for abdominal and
      bowel symptoms in IBS-C.
- name: Rifaximin
  description: Non-absorbable antibiotic for IBS-D with bloating.
  evidence:
  - reference: PMID:21208106
    reference_title: "Rifaximin therapy for patients with irritable bowel syndrome without constipation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Among patients who had IBS without constipation, treatment with
      rifaximin for 2 weeks provided significant relief of IBS symptoms, bloating,
      abdominal pain, and loose or watery stools."
    explanation: The TARGET phase 3 trials show the minimally absorbed antibiotic
      rifaximin relieves global IBS symptoms and bloating in non-constipated IBS.
- name: Tricyclic Antidepressants
  description: Low-dose for pain modulation.
  evidence:
  - reference: PMID:24935275
    reference_title: "Effect of antidepressants and psychological therapies, including hypnotherapy,
      in irritable bowel syndrome: systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "with similar treatment effects for both tricyclic
      antidepressants and selective serotonin reuptake inhibitors."
    explanation: Meta-analysis of RCTs demonstrating that tricyclic antidepressants
      are an effective treatment for IBS.
- name: SSRIs
  description: For patients with comorbid anxiety/depression.
  evidence:
  - reference: PMID:24935275
    reference_title: "Effect of antidepressants and psychological therapies, including hypnotherapy,
      in irritable bowel syndrome: systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "with similar treatment effects for both tricyclic
      antidepressants and selective serotonin reuptake inhibitors."
    explanation: The same meta-analysis found selective serotonin reuptake inhibitors
      to have treatment effects comparable to tricyclic antidepressants in IBS.
- name: Probiotics
  description: May help some patients.
  evidence:
  - reference: PMID:19091823
    reference_title: "The efficacy of probiotics in the treatment of irritable bowel syndrome: a systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Probiotics appear to be efficacious in IBS, but the magnitude of
      benefit and the most effective species and strain are uncertain."
    explanation: Systematic review of RCTs indicating probiotics are efficacious in
      IBS, while the optimal strain remains uncertain.
- name: Antihistamines
  description: >
    H1 receptor antagonists for mast cell-mediated symptoms. Mast cell
    mediators including histamine contribute to visceral hypersensitivity
    and abdominal pain in IBS. Antihistamines are emerging as a
    barrier-restoration strategy targeting mast cell dysfunction.
  evidence:
  - reference: PMID:42413530
    reference_title: "Barrier restoration as a therapeutic strategy for disorders of gut-brain interaction."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "novel therapeutics, including antihistamines, mast cell stabilisers,
      protease inhibitors, secretagogues, and guanylate cyclase C agonists"
    explanation: Recent review identifies antihistamines as novel therapeutic
      agents for barrier restoration in disorders of gut-brain interaction.
- name: Mast Cell Stabilizers
  description: >
    Agents that prevent mast cell degranulation and release of mediators
    (histamine, tryptase) that excite visceral sensory neurons. Elevated
    mast cell activation is a key driver of symptoms in a subset of IBS
    patients, making stabilizers a rational barrier-protective approach.
  evidence:
  - reference: PMID:42413530
    reference_title: "Barrier restoration as a therapeutic strategy for disorders of gut-brain interaction."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "novel therapeutics, including antihistamines, mast cell stabilisers,
      protease inhibitors, secretagogues, and guanylate cyclase C agonists"
    explanation: Recent review identifies mast cell stabilizers as novel
      therapeutic agents for barrier restoration in disorders of gut-brain
      interaction.
- name: Cognitive Behavioral Therapy
  description: Effective for gut-brain axis modulation.
  evidence:
  - reference: PMID:24935275
    reference_title: "Effect of antidepressants and psychological therapies, including hypnotherapy,
      in irritable bowel syndrome: systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cognitive behavioral therapy, hypnotherapy, multicomponent psychological
      therapy, and dynamic psychotherapy were all beneficial."
    explanation: Meta-analysis evidence that cognitive behavioral therapy is a
      beneficial psychological therapy for IBS, consistent with gut-brain modulation.
datasets:
# Rectal mucosa transcriptome in chronic IBS
- accession: geo:GSE36701
  title: Gene expression analysis of rectal mucosa in chronic irritable bowel
    syndrome (IBS) compared to healthy volunteers (HV)
  description: >-
    Microarray analysis of rectal mucosal biopsies from patients with chronic
    IBS and healthy volunteers to identify differentially expressed genes
    related to intestinal barrier function and visceral hypersensitivity.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: MICROARRAY
  sample_types:
  - preferred_term: rectal mucosa biopsy
    term:
      id: UBERON:0001052
      label: rectum
    tissue_term:
      preferred_term: rectum
      term:
        id: UBERON:0001052
        label: rectum
  conditions:
  - chronic IBS
  - healthy controls
  platform: Affymetrix Human Genome U133 Plus 2.0 Array
  notes: >-
    Widely used IBS dataset for biomarker discovery. Key targets
    identified include EGFR, VEGFA, BCL2L1, CASP9, MMP9, MAPK14.

# IBS-D pilot microarray study
- accession: geo:GSE14841
  title: Expression data from healthy volunteers and IBS patients
  description: >-
    Microarray profiling of jejunal mucosal biopsies from 5 IBS-D
    patients and 4 healthy volunteers as a pilot study to characterize
    gene expression patterns in diarrhea-predominant IBS.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: MICROARRAY
  sample_types:
  - preferred_term: jejunal mucosa biopsy
    term:
      id: UBERON:0002115
      label: jejunum
    tissue_term:
      preferred_term: jejunum
      term:
        id: UBERON:0002115
        label: jejunum
  sample_count: 9
  conditions:
  - IBS-D (diarrhea-predominant)
  - healthy controls
  notes: >-
    Smaller pilot dataset often combined with GSE36701 for meta-analysis.
    Studies have identified 1257 differentially expressed genes between
    IBS-D and controls.

# IBS gut microbiota 16S sequencing
- accession: bioproject:PRJNA566284
  title: IBS gut microbiota and metabolome profiling
  description: >-
    16S rRNA gene sequencing of fecal samples from IBS patients and
    healthy controls at Beijing Friendship Hospital to investigate
    gut microbiota composition and identify potential biomarkers.
  organism:
    preferred_term: human gut metagenome
    term:
      id: NCBITaxon:408170
      label: human gut metagenome
  data_type: WGS
  sample_types:
  - preferred_term: fecal sample
    term:
      id: UBERON:0001988
      label: feces
    tissue_term:
      preferred_term: feces
      term:
        id: UBERON:0001988
        label: feces
  sample_count: 29
  conditions:
  - IBS patients
  - healthy controls
  notes: >-
    Combined with metabolomics data to investigate mechanisms underlying
    IBS through microbiologic and metabolomic profiling. This is 16S rRNA
    amplicon sequencing, not shotgun metagenomics; data_type is recorded as WGS
    because DatasetTypeEnum has no amplicon-sequencing value.

# American Gut Project IBS subset
- accession: mgnify:MGYS00000596
  title: American Gut Project
  description: >-
    16S rRNA V4 region sequencing from the American Gut Project citizen
    science initiative. Contains 942 IBS subjects (IBS-D, IBS-C, IBS-U
    subtypes) matched with 942 non-IBS controls by age, gender, BMI,
    geography, and dietary patterns.
  organism:
    preferred_term: human gut metagenome
    term:
      id: NCBITaxon:408170
      label: human gut metagenome
  data_type: WGS
  sample_types:
  - preferred_term: fecal sample
    term:
      id: UBERON:0001988
      label: feces
    tissue_term:
      preferred_term: feces
      term:
        id: UBERON:0001988
        label: feces
  sample_count: 1884
  conditions:
  - IBS-D (diarrhea-predominant)
  - IBS-C (constipation-predominant)
  - IBS-U (unclassified)
  - healthy controls
  publication: PMID:36573834
  notes: >-
    Large-scale microbiome study showing IBS-D and IBS-U have reduced
    bacterial diversity (Shannon index). Identifies associations between
    gut microbiota and depression in IBS subtypes. Bifidobacterium and
    SCFA pathways reduced in IBS with depression
references:
- reference: DOI:10.1080/17425255.2024.2349716
  title: 'Pharmacogenetics in IBS: update and impact of GWAS studies in drug targets
    and metabolism'
  findings: []
- reference: DOI:10.1136/gutjnl-2022-328515
  title: 'Irritable bowel syndrome: treatment based on pathophysiology and biomarkers'
  findings: []
- reference: DOI:10.3390/jcm12072558
  title: 'Irritable Bowel Syndrome and the Gut Microbiome: A Comprehensive Review'
  findings: []
- reference: DOI:10.3390/medicina61010109
  title: 'Impact of Microbiota on Irritable Bowel Syndrome Pathogenesis and Management:
    A Narrative Review'
  findings: []
- reference: DOI:10.3390/nu17010155
  title: 'Exploring Gut Microbiota Imbalance in Irritable Bowel Syndrome: Potential
    Therapeutic Effects of Probiotics and Their Metabolites'
  findings: []
📚

References & Deep Research

References

5
DOI:10.1080/17425255.2024.2349716
Pharmacogenetics in IBS: update and impact of GWAS studies in drug targets and metabolism
No top-level findings curated for this source.
DOI:10.1136/gutjnl-2022-328515
Irritable bowel syndrome: treatment based on pathophysiology and biomarkers
No top-level findings curated for this source.
DOI:10.3390/jcm12072558
Irritable Bowel Syndrome and the Gut Microbiome: A Comprehensive Review
No top-level findings curated for this source.
DOI:10.3390/medicina61010109
Impact of Microbiota on Irritable Bowel Syndrome Pathogenesis and Management: A Narrative Review
No top-level findings curated for this source.
DOI:10.3390/nu17010155
Exploring Gut Microbiota Imbalance in Irritable Bowel Syndrome: Potential Therapeutic Effects of Probiotics and Their Metabolites
No top-level findings curated for this source.

Deep Research

2

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Disorder ▸

Disorder

  • Name: Irritable Bowel Syndrome
  • Category: Complex
  • Existing deep-research providers: falcon
  • Existing evidence reference count in YAML: 24

Key Pathophysiology Nodes

  • Visceral Hypersensitivity
  • Gut Dysmotility
  • Gut-Brain Axis Dysfunction
  • Intestinal Barrier Dysfunction
  • Immune Activation and Mast Cell Degranulation
  • Microbiome Dysbiosis
  • Deep research literature mapping

Citation Inventory (for evidence mapping)

  • DOI:10.1080/17425255.2024.2349716
  • DOI:10.1136/gutjnl-2022-328515
  • DOI:10.3390/jcm12072558
  • DOI:10.3390/medicina61010109
  • DOI:10.3390/nu17010155
Falcon ▸
Pathophysiology description (current understanding)
Edison Scientific Literature 18 citations 2025-12-17T23:34:33.115004

Pathophysiology description (current understanding) IBS is a multifactorial DGBI characterized by altered bidirectional signaling across the gut–brain–microbiome axis. Core mechanisms include visceral hypersensitivity, mucosal immune activation with mast-cell mediators, epithelial barrier dysfunction, dysregulated enteroendocrine (serotonergic) signaling, altered microbial ecology and metabolites (e.g., SCFAs and bile acids), and central modulation of pain and affect. Contemporary reviews and transcriptomic studies in IBS (particularly IBS-D) show upregulation of immune/inflammatory and nociceptive pathways (including TRPV1), barrier-related changes, and mediator release that sensitizes enteric afferents and facilitates pain (hyperalgesia), while bile acid diarrhea (BAD) represents a defined mechanistic subset with FXR–FGF19 signaling disturbances and enhanced mucosal immune activation by dihydroxy bile acids (e.g., chenodeoxycholic, deoxycholic acids) (Camilleri & Boeckxstaens 2023, Gut, Oct 2023; https://doi.org/10.1136/gutjnl-2022-328515) (camilleri2023irritablebowelsyndrome pages 6-8). The brain–gut axis integrates psychosocial stress, HPA activation, and inflammatory mediators, with high psychiatric comorbidity and heightened central pain processing contributing to symptom severity (Shaikh et al. 2023, J Clin Med; https://doi.org/10.3390/jcm12072558) (shaikh2023irritablebowelsyndrome pages 4-5).

1) Core pathophysiology - Visceral hypersensitivity • IBS patients demonstrate lower pain thresholds to recto-colonic distension; transcriptomics in IBS-D highlight upregulation of TRPV1 and neurotransmission genes, consistent with hyperexcitability of visceral afferents (Camilleri & Boeckxstaens 2023, Gut) (camilleri2023irritablebowelsyndrome pages 6-8). • Clinical and experimental evidence links neurotrophins (e.g., BDNF), prostaglandins (PGE2), and mast-cell mediators to heightened nociception (McKevitt 2024, colonic mucosa gene-expression review) (mckevitt2024investigatinggeneexpression pages 24-27).

  • Immune activation and mast cells • Mucosal B cells/plasma cells and mast cells increase adjacent to nerves; augmented release of histamine, tryptase, and other mediators heightens neuronal excitability and visceral pain (Camilleri & Boeckxstaens 2023, Gut) (camilleri2023irritablebowelsyndrome pages 6-8). • Multiple studies report increased stool tryptase and localized mast-cell degranulation correlating with pain severity (McKevitt 2024; Mansilla et al. 2024, Nutrients; https://doi.org/10.3390/nu17010155) (mckevitt2024investigatinggeneexpression pages 20-24, mansilla2024exploringgutmicrobiota pages 2-4).

  • Epithelial barrier dysfunction • Increased permeability is documented in IBS, especially in BAD versus IBS-D without BAD; colonic and small-bowel segmental permeability can be inferred from timed urinary sugar probes (Camilleri & Boeckxstaens 2023, Gut) (camilleri2023irritablebowelsyndrome pages 6-8). • Barrier-protein transcripts and tight-junction remodeling are variably altered across IBS subtypes (OCLN/CLDN1 increases in IBS-C with greater integrity; loss in IBS-D), and innate-sensing TLRs are dysregulated (McKevitt 2024) (mckevitt2024investigatinggeneexpression pages 20-24).

  • Microbiome and metabolites • Dysbiosis with reduced beneficial taxa (e.g., Bifidobacterium, Faecalibacterium prausnitzii) and altered Firmicutes:Bacteroidetes balance are repeatedly observed, with mechanistic links to immune activation, oxidative stress, and permeability (Mansilla et al. 2024, Nutrients) (mansilla2024exploringgutmicrobiota pages 2-4). • SCFAs regulate epithelial transport, immune differentiation (e.g., Treg induction), and serotonergic gene expression (TPH1/SERT); butyrate can increase SERT in vitro, whereas acetate/propionate may decrease SERT expression; SCFAs also exert epigenetic effects (histone acetylation) modulating NF-κB/TNF-α (McKevitt 2024) (mckevitt2024investigatinggeneexpression pages 27-31).

  • Bile acids and FXR–FGF19/TGR5 signaling (particularly in IBS-D/BAD) • BAD denotes ~subset of IBS-D with increased fecal bile acids and reduced FXR–FGF19 feedback; mucosa exhibits greater immune activation, partly attributable to bile acid detergency (Camilleri & Boeckxstaens 2023, Gut) (camilleri2023irritablebowelsyndrome pages 6-8).

  • Serotonin pathway (enterochromaffin) • About 95% of 5-HT is produced in GI tissues; IBS shows altered expression of serotonergic genes (TPH1, SLC6A4/SERT, HTRs) and associations with bowel habit phenotypes (McKevitt 2024) (mckevitt2024investigatinggeneexpression pages 24-27). SCFAs can modulate TPH1/SERT (McKevitt 2024) (mckevitt2024investigatinggeneexpression pages 27-31).

  • Brain–gut axis and central modulation • Psychiatric comorbidity is frequent; stress and HPA activation (elevated IL-6/IL-8) can worsen gut symptoms via effects on motility, permeability, and nociception (Shaikh et al. 2023) (shaikh2023irritablebowelsyndrome pages 4-5).

2) Key molecular players - Genes/Proteins (HGNC) • TRPV1 (HGNC:12350): upregulated in IBS-D transcriptomes; mediator of nociceptive hypersensitivity (Gut 2023) (camilleri2023irritablebowelsyndrome pages 6-8). • CLDN family (e.g., CLDN1; HGNC:2045), OCLN (HGNC:8101), TJP1/ZO-1 (HGNC:11773): barrier integrity/remodeling in IBS subtypes (McKevitt 2024) (mckevitt2024investigatinggeneexpression pages 20-24). • SLC6A4 (SERT; HGNC:11050), TPH1 (HGNC:12016): serotonergic transport/synthesis altered in IBS; SCFAs modulate expression (McKevitt 2024) (mckevitt2024investigatinggeneexpression pages 27-31, mckevitt2024investigatinggeneexpression pages 24-27). • FXR/NR1H4 (HGNC:7965), FGF19 (HGNC:3680), GPBAR1/TGR5 (HGNC:4518): bile acid signaling implicated in BAD and IBS-D (Gut 2023) (camilleri2023irritablebowelsyndrome pages 6-8). • BDNF (HGNC:1033): linked to visceral pain and enteric signaling (McKevitt 2024) (mckevitt2024investigatinggeneexpression pages 24-27). • Immune mediators: TNF (HGNC:11892), IL6 (HGNC:6018), IL1B (HGNC:5992); increased cytokine activity associated with symptoms and stress (Shaikh 2023) (shaikh2023irritablebowelsyndrome pages 4-5); evidence for TNFSF15 and immune loci in IBS genetics (Camilleri & Jencks 2024) (camilleri2024pharmacogeneticsinibs pages 16-18).

  • Chemical entities (CHEBI) • SCFAs: acetate (CHEBI:15343), propionate (CHEBI:15986), butyrate (CHEBI:17148); immunoepithelial and epigenetic modulators (McKevitt 2024) (mckevitt2024investigatinggeneexpression pages 27-31). • Bile acids: chenodeoxycholic acid/CDCA (CHEBI:16755), deoxycholic acid/DCA (CHEBI:29807); mucosal irritants promoting BAD immune activation (Gut 2023) (camilleri2023irritablebowelsyndrome pages 6-8). • Histamine (CHEBI:18295) and tryptase (e.g., TPSAB1 gene product): mast-cell mediators linked to pain (Gut 2023; Mansilla 2024) (camilleri2023irritablebowelsyndrome pages 6-8, mansilla2024exploringgutmicrobiota pages 2-4).

  • Cell types (CL) • Enterochromaffin cells (CL:0000160), intestinal epithelial cells (CL:0002253), mucosal mast cells (CL:0000097), enteric neurons (CL:0000393) (mechanistic roles per Gut 2023; McKevitt 2024) (camilleri2023irritablebowelsyndrome pages 6-8, mckevitt2024investigatinggeneexpression pages 24-27).

  • Anatomical locations (UBERON) • Colon (UBERON:0001155), small intestine (UBERON:0002108), lamina propria (UBERON:0001969), enteric nervous system (UBERON:0001799) (Gut 2023; McKevitt 2024) (camilleri2023irritablebowelsyndrome pages 6-8, mckevitt2024investigatinggeneexpression pages 24-27).

3) Biological processes (GO terms) disrupted - Sensory perception of pain/visceral nociception (GO:0019233): TRPV1-mediated hypersensitivity (Gut 2023) (camilleri2023irritablebowelsyndrome pages 6-8). - Inflammatory response (GO:0006954) and mast-cell activation (GO:0045576): immune mediator release driving neuronal excitability (Gut 2023) (camilleri2023irritablebowelsyndrome pages 6-8). - Regulation of intestinal epithelial cell–cell adhesion (GO:0098609) and tight junction assembly (GO:0070830): barrier dysfunction in IBS subtypes/BAD (Gut 2023; McKevitt 2024) (camilleri2023irritablebowelsyndrome pages 6-8, mckevitt2024investigatinggeneexpression pages 20-24). - Serotonin metabolic process (GO:0042428) and monoamine transport (GO:0015844): altered EC signaling (McKevitt 2024) (mckevitt2024investigatinggeneexpression pages 24-27). - Bile acid mediated signaling pathway (GO:1905114): FXR–FGF19/TGR5 dysregulation in BAD/IBS-D (Gut 2023) (camilleri2023irritablebowelsyndrome pages 6-8). - Regulation of T cell differentiation, including Treg (GO:0045580): SCFA-driven immune modulation (McKevitt 2024) (mckevitt2024investigatinggeneexpression pages 27-31).

4) Cellular components (GO) - Tight junction (GO:0005923): ZO-1/TJP1, claudins, occludin localization changes (McKevitt 2024) (mckevitt2024investigatinggeneexpression pages 20-24). - Extracellular space (GO:0005615): mediator milieu (histamine, proteases, cytokines) sensitizing afferents (Gut 2023) (camilleri2023irritablebowelsyndrome pages 6-8). - Plasma membrane and ion channel complexes (GO:0005886; GO:1902495): TRPV1 and other nociceptive channels (Gut 2023) (camilleri2023irritablebowelsyndrome pages 6-8).

5) Disease progression: sequence of events - Triggers (e.g., acute enteric infection, psychosocial stress) perturb microbiota and barrier integrity, increasing antigen exposure and activating mucosal immune cells (mast cells, B/plasma cells). Released mediators (histamine, tryptase, prostaglandins) and epithelial factors sensitize TRPV1-expressing afferents, producing visceral hypersensitivity. Concurrently, enteroendocrine serotonin signaling and bile acid pathways shape motility and secretion (IBS-D vs IBS-C). Central circuits (BGA) amplify pain and hypervigilance, reinforced by psychiatric comorbidities. In a subset (BAD), impaired FXR–FGF19 feedback increases colonic dihydroxy bile acids, further disrupting barrier and activating mucosal immunity (Camilleri & Boeckxstaens 2023; Shaikh 2023) (camilleri2023irritablebowelsyndrome pages 6-8, shaikh2023irritablebowelsyndrome pages 4-5).

6) Phenotypic manifestations (HP terms) and mechanistic links - Abdominal pain (HP:0002027) and visceral hyperalgesia (HP:0025387): TRPV1 upregulation, mast-cell mediator release, central sensitization (Gut 2023; McKevitt 2024) (camilleri2023irritablebowelsyndrome pages 6-8, mckevitt2024investigatinggeneexpression pages 24-27). - Diarrhea (HP:0002014) in IBS-D, including bile acid diarrhea: increased luminal bile acids with FXR–FGF19 dysregulation (Gut 2023) (camilleri2023irritablebowelsyndrome pages 6-8). - Constipation (HP:0002019) in IBS-C: altered serotonergic transport/synthesis and neuromuscular signaling (McKevitt 2024) (mckevitt2024investigatinggeneexpression pages 24-27). - Bloating and distension (HP:0003270): dysbiosis, fermentation, barrier permeability (Mansilla 2024; McKevitt 2024) (mansilla2024exploringgutmicrobiota pages 2-4, mckevitt2024investigatinggeneexpression pages 20-24). - Anxiety/depression comorbidity (HP:0000739/HP:0000716): BGA dysregulation and HPA-axis stress–inflammation link (Shaikh 2023) (shaikh2023irritablebowelsyndrome pages 4-5).

Genetics and ion channels - IBS is polygenic with modest heritability. Recent overviews emphasize immune-related loci (e.g., TNFSF15), motility/stool-frequency signals, and neuronal/neurotrophic pathways in ENS and pain modulation; these provide theoretical targets for precision therapeutics though clinical pharmacogenomic stratification remains limited to drug-metabolizing enzymes (e.g., CYP2D6/2C19) at present (Camilleri & Jencks 2024; Expert Opin Drug Metab Toxicol, May 2024; https://doi.org/10.1080/17425255.2024.2349716) (camilleri2024pharmacogeneticsinibs pages 16-18). - Ion-channel and nociceptive signaling (TRPV1) are consistently implicated in IBS-D hypersensitivity, with transcriptome-level upregulation and functional links to immune mediator exposure (Gut 2023) (camilleri2023irritablebowelsyndrome pages 6-8).

Brain–gut axis, neuroimaging, and psychiatric comorbidity - IBS shows high rates of anxiety/depression, with stress and inflammatory cytokines (IL-6, IL-8) linked to symptom exacerbation and altered motility/visceral pain processing—underscoring top-down modulation along the BGA (Shaikh 2023; Mar 2023; https://doi.org/10.3390/jcm12072558) (shaikh2023irritablebowelsyndrome pages 4-5).

Post-infectious IBS (PI-IBS) - Meta-analytic and narrative syntheses indicate an increased risk of PI-IBS (on the order of ~fourfold) following enteric infections, with persistent low-grade mucosal inflammation, immune activation (Th1/Th17 bias), and barrier defects proposed as drivers (Almonajjed et al. 2025, Medicina; https://doi.org/10.3390/medicina61010109) (almonajjed2025impactofmicrobiota pages 4-5).

Current applications and real-world implementations - Biomarker-guided care: BAD testing (serum C4/FGF19 where available; fecal bile acids) and empiric bile acid sequestrants or FXR-targeted approaches for IBS-D/BAD; mast-cell–directed strategies (e.g., non-sedating H1R antagonists) in patients with histamine-driven pain; barrier-directed nutrition and microbiota-modifying interventions (pre/probiotics, fiber) (Camilleri & Boeckxstaens 2023) (camilleri2023irritablebowelsyndrome pages 6-8). - Psychogastroenterology: integration of central neuromodulators and brain–gut behavioral therapies alongside diet/microbiome strategies given strong BGA contribution (Shaikh 2023) (shaikh2023irritablebowelsyndrome pages 4-5).

Expert opinions and analysis from authoritative sources - A state-of-the-art Gut review advocates individualized treatment guided by actionable mechanisms (transit abnormality, BAD, barrier dysfunction, immune activation/mast cells, microbiome) rather than symptom phenotype alone, citing multi-omics and mucosal transcriptomic evidence supporting immune–nociceptive–barrier triad in IBS-D and BAD (Camilleri & Boeckxstaens 2023, Gut) (camilleri2023irritablebowelsyndrome pages 6-8). - Pharmacogenetics perspective underscores that, while GWAS illuminate biological pathways (immune/ENS/motility), near-term precision medicine in IBS is more feasible via pharmacokinetic genotyping (e.g., CYP2D6/2C19 for central neuromodulators) and mechanism-targeted selection (Camilleri & Jencks 2024) (camilleri2024pharmacogeneticsinibs pages 16-18).

Relevant statistics and data (recent) - Transcriptomics: 181 genes (ascending colon) and 199 genes (rectosigmoid) differentially expressed in IBS-D vs controls, with upregulation of inflammation, TRPV1, neurotransmitter/receptor pathways; PI15/PI16 peptidase inhibitors reduced in IBS-D (Camilleri & Boeckxstaens 2023) (camilleri2023irritablebowelsyndrome pages 6-8). - Immune/neuronal proximity: Increased mast cells near nerves and mediator release linked to pain; proof-of-concept improvement with non-sedating H1 receptor antagonists (Camilleri & Boeckxstaens 2023) (camilleri2023irritablebowelsyndrome pages 6-8). - Psychiatric comorbidity: High prevalence of anxiety/depression in IBS cohorts and symptom exacerbation linked to stress cytokines (Shaikh 2023) (shaikh2023irritablebowelsyndrome pages 4-5). - Post-infectious risk: Approximately fourfold increased risk of IBS after enteric infection, with immune and barrier alterations persisting (Almonajjed 2025) (almonajjed2025impactofmicrobiota pages 4-5). - Serotonin and SCFAs: Butyrate upregulates SERT; acetate/propionate downregulate SERT in vitro; SCFAs promote Treg differentiation and modulate TNF/NF-κB signaling via epigenetic effects (McKevitt 2024) (mckevitt2024investigatinggeneexpression pages 27-31).

Evidence items (with PMIDs/DOIs/URLs; publication dates) - Camilleri M, Boeckxstaens G. Irritable bowel syndrome: treatment based on pathophysiology and biomarkers. Gut. 2023 Oct;72(3):590–599. doi:10.1136/gutjnl-2022-328515. URL: https://doi.org/10.1136/gutjnl-2022-328515 (mechanistic immune–barrier–TRPV1, BAD/FXR–FGF19, biomarker-guided therapy) (camilleri2023irritablebowelsyndrome pages 6-8). - Camilleri M, Jencks KJ. Pharmacogenetics in IBS: update and impact of GWAS studies in drug targets and metabolism. Expert Opin Drug Metab Toxicol. 2024 May;20(5):319–332. doi:10.1080/17425255.2024.2349716. URL: https://doi.org/10.1080/17425255.2024.2349716 (genetics, ENS mechanisms, translational precision medicine) (camilleri2024pharmacogeneticsinibs pages 16-18). - Shaikh SD et al. Irritable Bowel Syndrome and the Gut Microbiome: A Comprehensive Review. J Clin Med. 2023 Mar;12(7):2558. doi:10.3390/jcm12072558. URL: https://doi.org/10.3390/jcm12072558 (BGA, psychiatric comorbidity, stress–cytokine links) (shaikh2023irritablebowelsyndrome pages 4-5). - McKevitt EE. Investigating gene expression in the colonic mucosal tissue of individuals with disorders of gut–brain interaction. 2024 (preprint/unknown journal). Key mechanistic syntheses: barrier proteins (OCLN/CLDN1), TLRs, cytokines (TNF, IL-1β, IL-6), mast-cell activation (tryptase), serotonin pathway (TPH1/SLC6A4), neurotrophins (BDNF), SCFA modulation of SERT/TPH1 (mckevitt2024investigatinggeneexpression pages 20-24, mckevitt2024investigatinggeneexpression pages 27-31, mckevitt2024investigatinggeneexpression pages 24-27). - Mansilla MJG et al. Exploring Gut Microbiota Imbalance in IBS: Potential Therapeutic Effects of Probiotics and Their Metabolites. Nutrients. 2024 Dec;17(1):155. doi:10.3390/nu17010155. URL: https://doi.org/10.3390/nu17010155 (dysbiosis patterns; mast-cell correlates) (mansilla2024exploringgutmicrobiota pages 2-4). - Almonajjed MB et al. Impact of Microbiota on IBS Pathogenesis and Management: A Narrative Review. Medicina. 2025 Jan;61(1):109. doi:10.3390/medicina61010109. URL: https://doi.org/10.3390/medicina61010109 (PI-IBS risk, immune–barrier mechanisms) (almonajjed2025impactofmicrobiota pages 4-5).

Ontology-linked annotations (exemplars) - Genes/Proteins (HGNC): TRPV1; SLC6A4 (SERT); TPH1; NR1H4 (FXR); FGF19; GPBAR1 (TGR5); CLDN1; OCLN; TJP1; TNF; IL6; IL1B (camilleri2023irritablebowelsyndrome pages 6-8, camilleri2024pharmacogeneticsinibs pages 16-18, mckevitt2024investigatinggeneexpression pages 24-27, mckevitt2024investigatinggeneexpression pages 20-24, mckevitt2024investigatinggeneexpression pages 27-31). - Biological process (GO): inflammatory response (GO:0006954); bile acid mediated signaling (GO:1905114); serotonin metabolic process (GO:0042428); regulation of intestinal permeability (GO:1905499); sensory perception of pain (GO:0019233) (camilleri2023irritablebowelsyndrome pages 6-8, mckevitt2024investigatinggeneexpression pages 24-27). - Cellular component (GO): tight junction (GO:0005923); extracellular space (GO:0005615); ion channel complex (GO:1902495) (mckevitt2024investigatinggeneexpression pages 20-24, camilleri2023irritablebowelsyndrome pages 6-8). - Cell types (CL): mucosal mast cell (CL:0000097); enterochromaffin cell (CL:0000160); intestinal epithelial cell (CL:0002253); enteric neuron (CL:0000393) (camilleri2023irritablebowelsyndrome pages 6-8, mckevitt2024investigatinggeneexpression pages 24-27). - Anatomical locations (UBERON): colon (UBERON:0001155); small intestine (UBERON:0002108); lamina propria (UBERON:0001969); enteric nervous system (UBERON:0001799) (camilleri2023irritablebowelsyndrome pages 6-8, mckevitt2024investigatinggeneexpression pages 24-27). - Chemical entities (CHEBI): acetate (CHEBI:15343); propionate (CHEBI:15986); butyrate (CHEBI:17148); chenodeoxycholic acid (CHEBI:16755); deoxycholic acid (CHEBI:29807); histamine (CHEBI:18295) (mckevitt2024investigatinggeneexpression pages 27-31, camilleri2023irritablebowelsyndrome pages 6-8).

Notes and limitations - Where possible, 2023–2024 high-quality sources (Gut 2023; Expert Opin 2024) were prioritized. Some mechanistic syntheses (gene expression/SCFA–SERT modulation; PI-IBS estimate) derive from recent narrative/unknown-journal reviews; these highlight hypotheses needing continued validation. Neuroimaging- and subtype-specific genetic effect sizes were outside the scope of the retrieved evidence here and warrant further targeted review.

References

  1. (camilleri2023irritablebowelsyndrome pages 6-8): Michael Camilleri and Guy Boeckxstaens. Irritable bowel syndrome: treatment based on pathophysiology and biomarkers. Gut, 72:590-599, Oct 2023. URL: https://doi.org/10.1136/gutjnl-2022-328515, doi:10.1136/gutjnl-2022-328515. This article has 99 citations and is from a highest quality peer-reviewed journal.

  2. (shaikh2023irritablebowelsyndrome pages 4-5): Sofia D. Shaikh, Natalie Sun, Andrew Canakis, William Y. Park, and Horst Christian Weber. Irritable bowel syndrome and the gut microbiome: a comprehensive review. Journal of Clinical Medicine, 12:2558, Mar 2023. URL: https://doi.org/10.3390/jcm12072558, doi:10.3390/jcm12072558. This article has 146 citations and is from a poor quality or predatory journal.

  3. (mckevitt2024investigatinggeneexpression pages 24-27): EE McKevitt. Investigating gene expression in the colonic mucosal tissue of individuals with disorders of gut-brain interaction. Unknown journal, 2024.

  4. (mckevitt2024investigatinggeneexpression pages 20-24): EE McKevitt. Investigating gene expression in the colonic mucosal tissue of individuals with disorders of gut-brain interaction. Unknown journal, 2024.

  5. (mansilla2024exploringgutmicrobiota pages 2-4): María José García Mansilla, María Jesús Rodríguez Sojo, Andrea Roxana Lista, Ciskey Vanessa Ayala Mosqueda, Antonio Jesús Ruiz Malagón, Julio Gálvez, Alba Rodríguez Nogales, and María José Rodríguez Sánchez. Exploring gut microbiota imbalance in irritable bowel syndrome: potential therapeutic effects of probiotics and their metabolites. Nutrients, 17:155, Dec 2024. URL: https://doi.org/10.3390/nu17010155, doi:10.3390/nu17010155. This article has 13 citations and is from a poor quality or predatory journal.

  6. (mckevitt2024investigatinggeneexpression pages 27-31): EE McKevitt. Investigating gene expression in the colonic mucosal tissue of individuals with disorders of gut-brain interaction. Unknown journal, 2024.

  7. (camilleri2024pharmacogeneticsinibs pages 16-18): Michael Camilleri and Kara J Jencks. Pharmacogenetics in ibs: update and impact of gwas studies in drug targets and metabolism. Expert Opinion on Drug Metabolism & Toxicology, 20:319-332, May 2024. URL: https://doi.org/10.1080/17425255.2024.2349716, doi:10.1080/17425255.2024.2349716. This article has 1 citations and is from a peer-reviewed journal.

  8. (almonajjed2025impactofmicrobiota pages 4-5): Mhd Bashir Almonajjed, Mahdi Wardeh, Abdallah Atlagh, Abdulrahman Ismaiel, Stefan-Lucian Popa, Flaviu Rusu, and Dan L. Dumitrascu. Impact of microbiota on irritable bowel syndrome pathogenesis and management: a narrative review. Medicina, 61:109, Jan 2025. URL: https://doi.org/10.3390/medicina61010109, doi:10.3390/medicina61010109. This article has 10 citations and is from a poor quality or predatory journal.