Definition of Irritable bowel syndrome:

Irritable bowel syndrome (IBS) is a disorder that leads to abdominal pain and cramping, changes in bowel movements, and other symptoms.

IBS is not the same as inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis. In IBS, the structure of the bowel is not abnormal.

Causes, incidence, and risk factors:

It is not clear why patients develop IBS. Sometimes it occurs after an infection of the intestines. This is called postinfectious IBS. There may also be other triggers.

The intestine is connected to the brain. Signals go back and forth between the bowel and brain. These signals affect bowel function and symptoms. The nerves can become more active during stress, causing the intestines to be more sensitive and squeeze (contract) more.

IBS can occur at any age, but it often begins in the teen years or early adulthood. It is twice as common in women as in men.

About 1 in 6 people in the U.S. have symptoms of IBS. It is the most common intestinal problem that causes patients to be referred to a bowel specialist (gastroenterologist).