Overview
Irritable bowel syndrome is a common gut disorder causing recurrent abdominal pain or discomfort linked to bowel habit changes, without structural or biochemical abnormalities. It is a functional disorder, meaning the gut functions abnormally despite appearing normal on tests. IBS is chronic but not dangerous and does not increase cancer risk.
How common is it?
IBS affects around 10 to 20% of adults in the UK at any one time. It is more common in women and typically starts before age 50. It accounts for about 12% of GP consultations.
Causes and risk factors
IBS results from disturbed gut-brain communication, altered gut motility, visceral hypersensitivity, and in some cases changes in the gut microbiome.
Common risk factors
- Post-infectious IBS: following gastroenteritis (10 to 25% of cases)
- Gut-brain axis dysregulation and heightened pain sensitivity
- Altered gut motility (too fast or too slow)
- Gut microbiome changes
- Psychological factors: anxiety, depression, and adverse life events
- FODMAP intolerance (fermentable carbohydrates)
- Female sex hormones (flares common with menstruation)
- Family history
Symptoms
- Recurrent abdominal pain or discomfort, typically relieved by defecation
- Bloating and distension
- Diarrhoea (IBS-D), constipation (IBS-C), or alternating (IBS-M)
- Mucus in the stool
- Urgency to defecate
- Feeling of incomplete emptying
- Worsening with stress or particular foods
When to see a doctor
See a doctor if you have rectal bleeding, unexplained weight loss, onset after age 50, anaemia, or family history of bowel cancer, coeliac disease, or IBD. These are red flags requiring investigation to exclude serious pathology.
Diagnosis
IBS is diagnosed clinically using the Rome IV criteria, after excluding other causes. Blood tests (FBC, CRP, coeliac antibodies), faecal calprotectin to exclude IBD, and colonoscopy if red flags are present.
Treatments
Low-FODMAP diet
Reducing fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (found in wheat, onion, garlic, apples, lactose, and artificial sweeteners) significantly improves symptoms in 50 to 75% of patients. Should be supervised by a dietitian.
Antispasmodics
Mebeverine, hyoscine, or peppermint oil capsules reduce abdominal pain and spasm. Taken before meals or at onset of symptoms.
Laxatives and antidiarrhoeals
Ispaghula husk or laxatives for constipation-predominant IBS; loperamide for diarrhoea-predominant IBS.
Gut-directed psychological therapies
Cognitive behavioural therapy (CBT) and gut-directed hypnotherapy are as effective as drug treatment and produce lasting improvement, especially for anxiety-linked IBS.
Low-dose antidepressants
Tricyclic antidepressants (e.g. amitriptyline 10 to 30mg) or SSRIs reduce visceral hypersensitivity and pain independent of their antidepressant effect.
Self-care and lifestyle
- Eat regular meals and do not skip breakfast
- Limit fresh fruit to 3 portions per day
- Reduce caffeine, alcohol, and fizzy drinks
- Incorporate 30 minutes of aerobic exercise most days (proven to reduce IBS symptoms)
- Stress management and relaxation techniques
Prevention
IBS cannot be reliably prevented, but maintaining a balanced diet, managing stress, and prompt antibiotic treatment of gastroenteritis may reduce risk.