Now there's evidence that their underlying problem may be due to the structure of their brains, says Emeran Mayer, MD, professor of medicine, physiology, and psychiatry at the University of California, Los Angeles.
"Discovering structural changes in the brain ... demonstrates an 'organic' component to IBS and supports the concept of a brain-gut disorder," Mayer says in a news release. "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."
Mayer, David A. Seminowicz, PhD, and colleagues at UCLA and Canada's McGill University used sophisticated scans to compare the brain anatomy of 55 women with moderate IBS to 48 age-matched healthy women.
The finding: Thinning grey matter -- the part of the brain rich in neurons -- in specific areas of the brain. The affected areas involve:
- Dampening the brain's arousal system. IBS patients tend to be over-sensitive to (and hypervigilant for) bowel sensations.
- Controlling emotion. Symptom-related worries and ineffective coping strategies play an important role in chronic pain syndromes.
- Controlling pain. Brain thinning in this region was seen only in patients who listed pain as their most bothersome IBS symptom.
The findings, Seminowicz and colleagues suggest, point to a difference between IBS and chronic pain syndromes such as fibromyalgia.
In chronic pain syndromes, nerves constantly send increased pain signals to the brain. But in IBS, the brain itself seems to be amplifying pain signals it receives from the bowel.
The researchers say future studies should look at family members of IBS patients, to see if they inherited the same brain anatomy that may increase a person's risk of IBS. If so, the studies may reveal genetic components of IBS and point the way to new treatments.
The study appears in the July issue of the journal Gastroenterology.