Irritable Bowel Syndrome (IBS)
Symptoms, Causes & Treatment
Irritable Bowel Syndrome (IBS) affects 10–20% of adults and is one of the most common reasons for GP consultation worldwide. It is a real, recognised condition causing significant impact on quality of life. With the right management, most people with IBS achieve excellent symptom control.
What is IBS?
IBS is a functional gastrointestinal disorder characterised by chronic abdominal pain and altered bowel habits in the absence of structural or inflammatory pathology. The Rome IV criteria define IBS as recurrent abdominal pain at least 1 day per week for 3 months, associated with a change in stool frequency or form, or pain related to defecation. Three subtypes are recognised: IBS-C (constipation-predominant), IBS-D (diarrhoea-predominant), and IBS-M (mixed).
Symptoms of IBS
IBS symptoms are characteristically chronic, fluctuating, and related to bowel function. Symptoms that are new or changing require reassessment.
Recurrent abdominal pain or cramping · Bloating and abdominal distension · Altered bowel habit (diarrhoea, constipation, or both) · Mucus in stools · Urgency to open bowels · Symptoms relieved by defecation · Symptoms present for more than 6 months
Unexplained rectal bleeding · Unexplained weight loss · Fever with bowel symptoms · Waking at night with diarrhoea · Anaemia with GI symptoms · Onset of IBS-type symptoms over age 50 — all require investigation to exclude IBD or colorectal cancer
Rectal bleeding · Unexplained weight loss · Fever with bowel changes · Nocturnal diarrhoea · New symptoms over age 50 — these are red flags requiring urgent GP review to exclude cancer or IBD.
What Causes IBS?
IBS is a multifactorial functional disorder involving visceral hypersensitivity, gut-brain axis dysfunction, altered gut microbiome, and dietary sensitivities.
IBS is a functional disorder characterised by recurrent abdominal pain related to defecation, with altered bowel habits, in the absence of organic pathology. The Rome IV criteria require symptoms present for at least 6 months with onset at least 6 months ago.
The gut-brain axis is a bidirectional communication system between the enteric nervous system and the CNS. Stress, anxiety, and depression alter gut motility, visceral sensitivity, and microbiome composition, driving IBS symptoms.
Post-infectious IBS develops in 5–10% of people following acute bacterial gastroenteritis (Campylobacter, Salmonella, E. coli). The risk is higher after severe infection, prolonged symptoms, and in women and anxious individuals.
Altered gut microbiome composition (dysbiosis) is present in IBS. SIBO coexists in a significant proportion. Dietary interventions targeting FODMAP fermentation — the low-FODMAP diet — reduce symptoms in 75% of IBS patients.
Visceral hypersensitivity — exaggerated pain response to normal intestinal stimuli — is the hallmark of IBS. It results from peripheral sensitisation of gut nociceptors and central sensitisation in the dorsal horn and brain.
Hormonal fluctuations in the menstrual cycle significantly worsen IBS in women. Oestrogen and progesterone modulate gut motility and visceral sensitivity. Many women with IBS note worsening symptoms premenstrually.
Key Risk Factors
Diagnosing IBS
IBS is a positive clinical diagnosis using Rome IV criteria, after excluding IBD (calprotectin), coeliac disease (TTG IgA), and other organic conditions.
Treatment for IBS
IBS requires a multimodal approach: dietary modification, pharmacological symptom control, and psychological therapy for moderate-to-severe disease.
Supportive Measures
Keep a food and symptom diary. Follow a low-FODMAP diet supervised by a dietitian. Exercise regularly. Use antispasmodics for cramping. Practice stress management and mindfulness. Maintain a regular bowel routine. Heat packs help abdominal cramping.
Long-Term IBS Management
IBS is a long-term condition requiring ongoing management. Annual GP review, dietitian input, and psychological support (CBT or gut-directed hypnotherapy) improve long-term outcomes. Most people with IBS can achieve good quality of life with appropriate treatment.
When to Seek Help
Rectal bleeding · Unexplained weight loss · Fever with bowel symptoms · Nocturnal diarrhoea waking from sleep · IBS-type symptoms presenting over age 50 — see a GP urgently to exclude serious pathology.
See a GP if IBS symptoms are newly developing, changing in character, or accompanied by any red flag feature. An online consultation is a good first step for established IBS needing medication review or dietitian referral.
Preventing IBS Flare-Ups
IBS flare-ups can be significantly reduced through dietary management, exercise, and psychological wellbeing strategies.
Follow a dietitian-supervised low-FODMAP diet for 6–8 weeks, then systematically reintroduce foods to identify your personal triggers. Only restrict FODMAPs long-term based on confirmed intolerance.
Regular aerobic exercise reduces IBS symptoms, improves gut motility, and reduces anxiety and depression, which are the most important perpetuating factors in IBS.
Identify and manage anxiety and depression with CBT, mindfulness, or medication where needed. Psychological wellbeing is the most important modifiable factor in IBS symptom severity and quality of life.
A food and symptom diary kept for 2–4 weeks identifies personal IBS food triggers. Dairy, wheat, onions, garlic, and carbonated drinks are the most common. Dietitian guidance prevents unnecessary restriction.
Probiotics (particularly Lactobacillus and Bifidobacterium species) reduce IBS bloating and pain in some patients. A 4-week trial of a specific probiotic product is reasonable if poorly controlled on other measures.
Annual review with a GP allows reassessment of IBS symptoms, exclusion of new organic pathology, and adjustment of dietary and pharmacological management as symptoms change over time.
Getting Treatment for IBS
A GP can diagnose IBS, arrange initial investigations, prescribe antispasmodics, refer to a dietitian for low-FODMAP therapy, and arrange CBT or gut-directed hypnotherapy. Regular reviews optimise long-term management.
Expert clinical advice, when you need it.
IBS — Frequently Asked Questions
IBS is diagnosed using the Rome IV criteria: recurrent abdominal pain occurring at least 1 day per week for the last 3 months, associated with a change in stool frequency, a change in stool form, or pain related to defecation. Onset of symptoms must have been at least 6 months before diagnosis. All red flag features must be absent.
The low-FODMAP diet eliminates fermentable short-chain carbohydrates for 6–8 weeks, then systematically reintroduces each FODMAP group to identify personal triggers. Around 75% of IBS patients experience significant symptom improvement. It must be supervised by a FODMAP-trained dietitian to ensure nutritional completeness.
IBS is a real, recognised medical condition involving visceral hypersensitivity, gut dysmotility, altered gut microbiome, and gut-brain axis dysfunction. Symptoms are not imagined or psychological. However, psychological factors — anxiety, depression, and stress — significantly influence IBS severity through the gut-brain connection.
The most effective treatments are a low-FODMAP diet (75% response rate) and gut-directed cognitive behavioural therapy (CBT) or hypnotherapy. Antispasmodics (mebeverine) relieve cramping. Linaclotide helps IBS-C. Loperamide helps IBS-D. Low-dose amitriptyline reduces visceral pain. Most people need a combination of approaches.
Stress does not cause IBS, but it is one of the most powerful factors in worsening and perpetuating symptoms. Stress activates the gut-brain axis, altering gut motility, increasing visceral sensitivity, and modifying gut microbiome composition. Addressing stress through CBT, exercise, and mindfulness is a core part of IBS management.
Post-infectious IBS (PI-IBS) develops in approximately 5–10% of people following acute bacterial gastroenteritis (Campylobacter, Salmonella, E. coli). Symptoms begin after the infection resolves and may persist for years. Probiotic use during and after infection may reduce the risk.
IBS is a long-term condition that fluctuates over time. Many people experience periods of good control followed by flare-ups triggered by stress, dietary changes, or illness. Over the long term, the majority of IBS patients maintain a good quality of life with appropriate management and self-care strategies.
A GP can diagnose IBS, arrange tests to exclude other conditions (calprotectin, coeliac antibodies, blood tests), provide dietary advice, prescribe antispasmodics and other medications, and refer for CBT or dietitian support. Regular GP reviews optimise long-term management as symptoms change.