Irritable bowel syndrome—a brain disorder

Irritable bowel syndrome (IBS) can manifest with abdominal pain and diarrhea, or constipation, or both. A study just published in the journal Gastroenterology brings to light the role of the brain in IBS. The authors first observe:

"Several studies have examined structural brain changes associated with chronic pain syndromes, including irritable bowel syndrome (IBS), but study sample sizes have been small and heterogeneous."

They used MRI methods to examine anatomical differences in the brains of carefully screened IBS patients and normal 'controls'. Interestingly, they found significant abnormalities in the brains of the IBS group:

"IBS was associated with decreased gray matter density (GMD) in widespread areas of the brain [gray matter refers to the neuronal cell bodies]...The areas of decreased GMD associated with IBS were largely consistent across clinical subgroups, based on predominant bowel habit and pain predominance of symptoms."

The brain regions most affected included the prefrontal and posterior parietal cortices, leading to their conclusion:

"Changes in density of gray matter among regions involved in cognitive/evaluative functions are specifically observed in patients with IBS..."

Evaluation and treatment of irritable bowel syndrome, like so many other diverse conditions, must include the capacity of the brain to regulate its arousal state in general and the autonomic nervous system (which governs digestive and all other visceral functions) in particular.