REFERENCE · CO-OCCURRING CONDITION

Irritable Bowel Syndrome Alongside FND

This page covers: IBS: recurrent abdominal pain with changes in bowel habit, considered as a disorder of gut–brain interaction.

For the Person With FND
For Family, Friends, and Other Supporters
For Clinicians and the Care Team
Research and Sources —

For the Person With FND

Understanding gut–brain interaction

IBS can involve abdominal pain, bloating, constipation, diarrhoea or a mixture. The gut and brain constantly exchange signals. Changes in gut sensitivity, movement and central processing can all contribute; “gut–brain” does not mean the bowel is healthy in every respect or that symptoms are imagined. IBS has a positive clinical assessment pathway rather than requiring every conceivable test to be normal. [1]

The connection with FND principles is that symptoms can reflect altered regulation and processing across a system. Gut sensations can become unusually intrusive, while disrupted sleep, difficult meals and the urgency of finding a toilet can consume energy and attention. IBS is reported alongside FND, but co-occurrence does not prove that one causes the other. [1][2]

IBS is different from inflammatory bowel disease. The two can coexist, and changed symptoms in someone with an established bowel disease need the appropriate assessment. The emphasis here is on treatment after a workable clinical assessment, not a long list of exclusions. [1]

Recovery and management options

Match care to the bowel pattern: constipation-predominant, diarrhoea-predominant and mixed IBS need different plans. A clear explanation and shared priorities can help decide whether pain, stool consistency or urgency should be addressed first. [1] [Guideline-based practice]
Review meals and fibre: regular meals and individualized dietary advice are starting points. Soluble fibre may help, while simply adding more coarse bran can worsen symptoms for some people. Introduce changes gradually and review their effect. [1] [Guideline-based practice]
Consider a dietitian-supported low-FODMAP trial: this temporarily reduces certain fermentable carbohydrates, followed by reintroduction and personalization. It is not a permanent list of forbidden foods; avoid unnecessary restriction, especially with weight loss or an eating-disorder history. [1] [Guideline-based practice; low-certainty dietary evidence]
Use subtype-directed medicines: options may target constipation, diarrhoea or cramping. Clinicians may also use selected gut–brain neuromodulators to reduce pain sensitivity; their use does not require depression. Choice and adverse effects need individual review. [1] [Guideline-based practice; evidence varies by treatment]
IBS-focused CBT: this helps with the relationship between bowel symptoms, worry, responses and daily life. The treatment is designed for IBS, rather than assuming that generic stress advice will solve it. [1] [Research-supported guideline recommendation]
Gut-directed hypnotherapy: a trained practitioner uses an IBS-specific approach involving focused attention and suggestions about gut comfort and function. There is trial support, but benefit is not guaranteed and this does not validate every commercial hypnosis programme. [1] [Research-supported guideline recommendation]
Plan access around real life: reliable toilet access, flexible breaks and a workable meal plan can make FND rehabilitation and social activity possible. These supports should remain available while treatment is tried. [1][3] [Clinical guidance and individualized adaptation]

During a familiar flare: follow the bowel-specific plan and protect fluids, food access and rest. Rectal bleeding, unexplained weight loss, persistent vomiting or a substantial change in pattern needs clinical review rather than being dismissed as IBS or FND. [1]

For the Person With FND
For Family, Friends, and Other Supporters
For Clinicians and the Care Team
Research and Sources —

For Family, Friends, and Other Supporters

Believe the urgency and protect privacy. Help find toilets or adjust meal arrangements without monitoring every mouthful. The person should not have to disclose bowel symptoms repeatedly to receive a practical accommodation.

For the Person With FND
For Family, Friends, and Other Supporters
For Clinicians and the Care Team
Research and Sources —

For Clinicians and the Care Team

Make a positive IBS assessment with appropriate targeted investigation. Separate IBS from active inflammatory disease and other relevant causes; they may coexist. Integrate nutrition, medication, gut-directed therapies and disability access. Do not interpret response to CBT or hypnotherapy as proof that symptoms were psychological or part of FND. [1]

For the Person With FND
For Family, Friends, and Other Supporters
For Clinicians and the Care Team
Research and Sources —

Research and Sources

Evidence reviewed: September 23, 2026. The BSG guideline concerns IBS. Gut-directed behavioural therapy evidence supports symptom management, not a single shared FND mechanism; dietary evidence is less certain and restriction carries costs.

Technique labels describe the evidence for the named condition. A treatment working does not confirm an FND diagnosis or prove a shared mechanism.

No.	Source and stable record	What it supports and limits	Figure
1	Vasant DH, Paine PA, Black CJ, et al. British Society of Gastroenterology guidelines on the management of irritable bowel syndrome. Gut. 2021;70:1214–1240. doi:10.1136/gutjnl-2021-324598. FND-CIT-0208	IBS guideline: subtype-directed care, selected dietary approaches and gut–brain behavioural therapies. Evidence strength varies; restrictive diets need nutritional safeguards. Not proof of a common FND cause.	—
2	Steinruecke M, Mason I, Keen M, McWhirter L, Carson AJ, Stone J, Hoeritzauer I. Pain and functional neurological disorder: a systematic review and meta-analysis. Journal of Neurology, Neurosurgery & Psychiatry. 2024;95(9):874–885. https://doi.org/10.1136/jnnp-2023-332810 FND-CIT-0015	FND pain systematic review; co-occurrence and treatment burden, not proof of common causation.	—
3	Nicholson C, Edwards MJ, Carson AJ, et al. Occupational therapy consensus recommendations for functional neurological disorder. Journal of Neurology, Neurosurgery & Psychiatry. 2020;91(10):1037–1045. https://doi.org/10.1136/jnnp-2019-322281 FND-CIT-0011	Occupational therapy consensus for FND; practical adaptation, not proof of a specific component effect.	—

For the Person With FND
For Family, Friends, and Other Supporters
For Clinicians and the Care Team
Research and Sources —