Study finds structural brain alterations in patients with irritable bowel syndrome

A large academic study has demonstrated structural changes in specific brain regions in female patients with irritable bowel syndrome (IBS), a condition that causes pain and discomfort in the abdomen, along with diarrhea, constipation or both.

A collaborative effort between UCLA and Canada's McGill University, the study appears in the July issue of the journal Gastroenterology.

The findings show that IBS is associated with both decreases and increases in grey matter density in key areas of the brain involved in attention, emotion regulation, pain inhibition and the processing of visceral information.

IBS affects approximately 15 percent of the U.S. population, primarily women. Currently, the condition is considered by the medical field to be a "functional" syndrome of the digestive tract not working properly rather than an "organic" disorder with structural organ changes. Efforts to identify structural or biochemical alterations in the gut have largely been unsuccessful. Even though the pathophysiology is not completely understood, it is generally agreed that IBS represents an alteration in brain-gut interactions.

These study findings, however, show actual structural changes to the brain, which places IBS in the category of other pain disorders, such as lower back pain, temporomandibular joint disorder, migraines and hip pain — conditions in which some of the same anatomical brain changes have been observed, as well as other changes. A recent, smaller study suggested structural brain changes in IBS, but a larger definitive study hadn't been completed until now.

"Discovering structural changes in the brain, whether they are primary or secondary to the gastrointestinal symptoms, demonstrates an 'organic' component to IBS and supports the concept of a brain-gut disorder," said study author Dr. Emeran Mayer, professor of medicine, physiology and psychiatry at the David Geffen School of Medicine at UCLA. "Also, the finding removes the idea once and for all that IBS symptoms are not real and are 'only psychological.' The findings will give us more insight into better understanding IBS."

Researchers employed imaging techniques to examine and analyze brain anatomical differences between 55 female IBS patients and 48 female control subjects. Patients had moderate IBS severity, with disease duration from one to 34 years (average 11 years). The average age of the participants was 31.

Investigators found both increases and decreases of brain grey matter in specific cortical brain regions.

Even after accounting for additional factors such as anxiety and depression, researchers still discovered differences between IBS patients and control subjects in areas of the brain involved in cognitive and evaluative functions, including the prefrontal and posterior parietal cortices, and in the posterior insula, which represents the primary viscerosensory cortex receiving sensory information from the gastrointestinal tract.