Irritable Bowel Syndrome and the Gut–Brain Axis

Irritable bowel syndrome (IBS) is a group of symptoms that includes recurring abdominal pain and changes in bowel movements—diarrhea, constipation, or both. IBS does not mean symptoms are imagined. It is classified as a disorder of gut–brain interaction.

What may contribute to IBS

• Changes in bowel motility.
• Increased sensitivity to normal gas or stool.
• Prior gastrointestinal infection.
• Food sensitivities or intolerances in some people.
• Changes in gut microbes.
• Anxiety, depression, early-life adversity, or ongoing stress as possible contributors—not universal causes.
• Genetic and individual susceptibility.

How IBS is diagnosed

Clinicians can make a positive IBS diagnosis when recurring abdominal pain is linked to a change in stool frequency or form and the history and examination fit. Focused tests may be used to check for another condition—for example, celiac blood testing or inflammation testing when diarrhea is prominent or when alarm features are present. This is different from ordering every possible test before treatment begins.

Treatment is individualized

• Education and a clear diagnosis.
• Medication matched to the main pattern—diarrhea, constipation, pain, or combinations—selected with a clinician.
• Soluble fiber, increased gradually, when appropriate.
• For some people, a low-FODMAP diet trial: a 4–6 week restriction phase followed by reintroduction and personalization, ideally with a gastrointestinal dietitian.
• Regular meals, fluids, sleep, and activity.
• Cognitive behavioral therapy or gut-directed hypnotherapy for gut–brain symptom pathways; using these treatments does not mean symptoms are imagined.
• Review of treatment response and red flags over time.

Why behavioral treatment can help physical symptoms

Cognitive behavioral therapy and gut-directed hypnotherapy aim to change how pain, urgency, prediction, and avoidance interact across the gut–brain system. They can be used alongside diet or medication. Their use does not show that IBS is imagined or that stress caused every symptom.

Talk with a clinician about blood in stool, black stool, unintentional weight loss, anemia, persistent fever, repeated vomiting, nighttime symptoms, family history of inflammatory bowel disease or colorectal cancer, or a major change in symptoms.