Irritable bowel syndrome affects 10–15% of the UK population — up to 10 million people — yet it remains poorly understood and inconsistently treated. The NHS spends over £300 million annually on IBS care. A new wave of clinical trials is unpicking the gut-brain axis, the microbiome, and visceral pain mechanisms to develop truly effective treatments.
IBS is a functional gastrointestinal disorder, meaning standard tests often show no structural abnormality. Diagnosis and treatment have historically relied on symptom-based criteria (Rome IV). The UK has some of the world's leading IBS research centres, including the University of Manchester's GI Neuroscience group and King's College London's gut microbiome research.
There are currently over 70 actively recruiting IBS trials in the UK, spanning from diet-microbiome interactions and neuromodulation to novel pharmacological agents and psychological therapies.
Types of IBS Trials
Gut-Brain Axis
Neuromodulators, gut-directed hypnotherapy, CBT, and vagus nerve stimulation targeting the brain-gut connection.
Microbiome
Probiotics, prebiotics, faecal microbiota transplantation (FMT), and antibiotics targeting gut microbial composition.
Dietary
Low-FODMAP, gluten-free, fibre modulation, and elimination diet trials with personalised nutrition approaches.
Novel Pharmacotherapy
Guanylate cyclase agonists, ileal bile acid transporter inhibitors, and visceral pain modulators.
Gut-Brain Axis Therapies
The gut-brain axis is central to IBS — stress, mood, and visceral sensation are intimately linked. UK trials are exploring several approaches:
Gut-directed hypnotherapy — the Manchester-based approach pioneered by Professor Peter Whorwell continues to be refined in digital and group formats for broader NHS rollout
Cognitive behavioural therapy (CBT) for IBS — web and app-based CBT programmes designed specifically for IBS, with NHS-backed implementation trials
Neuromodulators (low-dose antidepressants) — trials comparing tricyclic antidepressants, SSRIs, and novel gut-acting drugs like prucalopride for visceral hypersensitivity
Non-invasive vagus nerve stimulation — transcutaneous VNS via ear or neck electrodes modulating the gut-brain vagal pathways
Mindfulness-based stress reduction — MBSR programmes adapted for IBS with a focus on symptom acceptance and visceral awareness
Microbiome Interventions
The gut microbiome in IBS is characteristically different from healthy controls, offering multiple therapeutic targets:
Faecal microbiota transplantation (FMT) — rigorous UK placebo-controlled trials of FMT for IBS-D and IBS-M, moving beyond the positive uncontrolled data
Targeted probiotics — trials of multi-strain and strain-specific probiotics (Bifidobacterium, Lactobacillus, Saccharomyces) with symptom-specific endpoints
Rifaximin — the non-absorbable antibiotic for IBS-D, in UK post-approval trials for repeat-course and long-term use protocols
Prebiotics and fermentable fibres — trials of galacto-oligosaccharides, inulin, and novel fibres in IBS patients to selectively promote beneficial bacteria
Bacteriophage therapy — very early-phase UK trials using phages to selectively target dysbiotic bacteria in IBS
Dietary and Lifestyle Trials
Diet is the most common self-management tool for IBS, and clinical trials are moving towards personalised nutrition:
Low-FODMAP diet optimisation — trials comparing low-FODMAP with traditional NICE dietary advice, and exploring re-introduction protocols for long-term use
Personalised carbohydrate modification — using breath test results (hydrogen/methane) to tailor dietary recommendations to individual fermentation patterns
Gluten-free diet without coeliac disease — trials examining non-coeliac gluten sensitivity in IBS patients, and whether gluten restriction improves symptoms
Fibre modulation — comparing insoluble (bran) with soluble (psyllium, linseed) fibre supplementation in IBS-C and IBS-D
Exercise and physical activity — trials of structured exercise programmes on IBS symptoms, gut motility, and quality of life
Visceral Pain Mechanisms
Pain is the most debilitating IBS symptom for many patients and remains the hardest to treat:
Transient receptor potential (TRP) channel modulators — drugs targeting TRPV1, TRPA1, and TRPM8 channels on gut sensory nerves
Peripheral mu-opioid receptor agonists — gut-restricted opioids like eluxadoline that reduce pain without central side effects
Serotonin type 3 and 4 receptor modulation — ondansetron for IBS-D (diarrhoea and pain) and prucalopride for IBS-C
Mast cell stabilisers — cromoglycate and ketotifen trials targeting mast cell activation in the gut wall
Bioelectronic therapies — implanted sacral nerve stimulators and percutaneous electrical nerve field stimulation for refractory IBS pain
IBS-D and IBS-C Specific Approaches
Treatment approaches differ significantly by bowel habit subtype:
IBS-D specific — eluxadoline, ondansetron, rifaximin, bile acid sequestrants (colesevelam), and novel opioid modulators
IBS-C specific — linaclotide, plecanatide, lubiprostone, prucalopride, and novel guanylate cyclase agonists
Mixed IBS (IBS-M) — trials evaluating treatments that work across both subtypes, including gut-brain therapies and microbiome modulation
Post-infectious IBS — a specific subtype triggered by gastroenteritis, with distinct trials exploring anti-inflammatory and immune-modulating approaches
Who Can Participate?
Eligibility typically requires meeting the Rome IV diagnostic criteria for IBS:
Rome IV diagnosis — recurrent abdominal pain at least one day per week for the last three months, associated with defecation, change in stool frequency, or change in stool form
Subtype classification — IBS-D, IBS-C, IBS-M (mixed), or IBS-U (unclassified). Many trials target a specific subtype, so accurate self-reporting of bowel habits is important
Exclusion of organic disease — recent normal colonoscopy (typically within 5–10 years depending on age), normal coeliac serology, normal inflammatory markers
Medication washout — some trials require a washout period for antispasmodics and other IBS medications
Exclusions — inflammatory bowel disease, coeliac disease, pregnancy, major psychiatric comorbidity (for drug trials), use of opioids or other constipating medications
💡 Tip: Track Your Symptoms Before Applying
Trial teams will want to see symptom diaries covering at least 2 weeks — documenting stool frequency, stool form (Bristol Stool Chart), pain severity (0–10 scale), and bloating. They will also need your medical history and any previous investigations (colonoscopy, coeliac bloods, FIT test). Many trials provide a smartphone app for symptom tracking during the screening phase.
UK IBS Trial Locations
Major UK centres running IBS trials include:
Manchester — Manchester University NHS Foundation Trust, home of the world-famous IBS Gut Hypnotherapy programme
London — King's College London, St Mark's Hospital (the UK's national bowel hospital), Barts, Imperial College
Nottingham — Queen's Medical Centre, Nottingham Digestive Diseases Centre
Oxford — John Radcliffe Hospital, Nuffield Department of Medicine
Newcastle — Newcastle upon Tyne Hospitals NHS Foundation Trust
Birmingham — University Hospitals Birmingham, Birmingham Biomedical Research Centre
Southampton — Southampton General Hospital, Human Development and Health research unit
Leeds — Leeds Teaching Hospitals, Leeds Gastroenterology Institute
How to Find Your Match
Use our Smart Matcher to find IBS trials tailored to your subtype (IBS-D, IBS-C, IBS-M), symptom severity, dietary preferences, and treatment history. Whether you are interested in gut-directed hypnotherapy, FODMAP management, or novel pharmacology, we can match you to actively recruiting studies.