Irritable bowel syndrome (IBS)

Irritable bowel syndrome (IBS) is a common disorder of gut–brain interaction characterized by recurrent abdominal pain related to defecation or associated with change in stool frequency or form. Unlike inflammatory bowel disease, IBS does not cause visible inflammation, ulcers, or permanent damage to the intestine.

IBS is classified by predominant stool pattern: IBS with constipation (IBS-C), IBS with diarrhea (IBS-D), mixed (IBS-M), or unclassified. Symptoms can significantly affect quality of life, work, and social functioning. A positive diagnosis based on symptom criteria, limited testing to exclude mimics, and a multimodal treatment plan focused on the most bothersome symptoms usually leads to meaningful improvement.

Key features include:

• Abdominal pain or discomfort, often related to bowel movements
• Bloating and gas
• Diarrhea, constipation, or alternating bowel habits
• Mucus in the stool
• Sensation of incomplete evacuation
• Symptoms that are typically chronic and fluctuating

Warning signs that suggest a different or additional diagnosis (and warrant further investigation) include unintentional weight loss, blood in the stool, fever, anemia, nocturnal symptoms that wake the person from sleep, onset after age 50, or a family history of colorectal cancer, inflammatory bowel disease, or celiac disease.

IBS does not have a single cause. Contributing mechanisms include:

• Altered gut motility
• Visceral hypersensitivity (heightened pain signaling from the gut)
• Gut–brain axis dysregulation and stress reactivity
• Low-grade immune activation or post-infectious changes in some people
• Alterations in the gut microbiome
• Food sensitivities (not classic IgE allergy) — FODMAPs are important triggers for many
• Genetic predisposition and early life factors

Psychological stress does not cause IBS by itself but commonly amplifies symptoms.

Risk factors include:

• Younger age (often begins in adolescence or early adulthood)
• Female sex
• Family history of IBS
• Anxiety, depression, or a history of physical or sexual abuse
• Prior severe gastrointestinal infection (post-infectious IBS)
• Stressful life events

IBS does not increase the risk of colorectal cancer or inflammatory bowel disease. The main burdens are:

• Impaired quality of life
• Work absenteeism and reduced productivity
• Restrictive eating patterns and, rarely, disordered eating
• Anxiety and depression related to chronic symptoms
• Unnecessary tests or treatments if the diagnosis is not clearly established

There is no proven way to prevent IBS. Managing stress, maintaining regular meals and sleep, and staying active may reduce symptom flares in people who already have the condition.

IBS is diagnosed using symptom-based criteria (Rome IV): recurrent abdominal pain, on average at least one day per week in the last three months, associated with two or more of: related to defecation, associated with change in stool frequency, or associated with change in stool form.

Limited testing is used to exclude other conditions when indicated:

• Complete blood count, C-reactive protein or fecal calprotectin (to help exclude inflammatory disease)
• Celiac serology
• Age-appropriate colorectal cancer screening
• Additional tests only if red flags are present or treatment fails

Routine colonoscopy is not required for typical IBS without alarm features in younger adults.

See a healthcare professional for recurrent abdominal pain with change in bowel habits lasting more than a few weeks, or if symptoms interfere with daily life. Seek prompt evaluation for any red-flag features listed above.

Treatment is tailored to the predominant symptoms and their impact:

Diet and lifestyle

• Regular meals; adequate soluble fiber for some with IBS-C
• Trial of a low-FODMAP diet under dietitian guidance, with systematic reintroduction
• Adequate hydration and physical activity
• Limiting alcohol, caffeine, and fatty trigger foods if relevant

Medicines (examples by symptom)

• IBS-C: polyethylene glycol, linaclotide, lubiprostone, plecanatide, tenapanor
• IBS-D: loperamide, eluxadoline, rifaximin (course), bile acid binders if indicated, alosetron (restricted use)
• Pain/bloating: antispasmodics, peppermint oil, low-dose tricyclic antidepressants or SNRIs
• Any subtype: gut-directed psychological therapies, including CBT and gut-directed hypnotherapy

A strong therapeutic relationship and realistic goals (improvement, not always perfect control) improve outcomes.

Practical steps:

• Keep a brief symptom and food diary to identify patterns
• Eat regular, not overly large, meals
• Try soluble fiber (e.g., psyllium) gradually if constipation predominates
• Manage stress with techniques that work for you
• Exercise regularly
• Avoid unnecessary restriction of many foods without professional guidance
• Use medicines as prescribed for breakthrough symptoms

Bring:

• Symptom pattern (pain, stool form using the Bristol scale if possible, bloating, triggers)
• List of medicines and prior treatments tried
• Any previous test results (blood work, stool tests, colonoscopy)
• Notes on diet and stress
• Questions about whether further testing is needed and which treatments fit your subtype