Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Irritable Bowel Syndrome (IBS)

What Is It?

Irritable bowel syndrome (IBS) is a common disorder that causes a variety of symptoms, including abdominal pain, diarrhea and/or constipation, bloating, gassiness, and cramping. Because these symptoms may be caused by a number of different bowel diseases, IBS is usually diagnosed only after your doctor determines you don't have a more serious problem.

The severity of the disorder varies from person to person. Some people experience symptoms that come and go and are just mildly annoying, while others have such severe daily bowel problems that IBS affects their ability to work, sleep and enjoy life. In addition, symptoms may change over time. A person may have severe symptoms for several weeks and then feel well for months or even years. Most people are never cured of IBS, but the disorder is not related to any other disease and does not develop into any other disease, such as ulcerative colitis or colon cancer.

IBS usually starts in early adulthood. It affects twice as many women as men. Approximately 10% to 20% of the population has IBS, but at least half of all people with the condition never seek medical care for their symptoms. No one knows what causes IBS. Some studies suggest that the nerves of the colon may be much more sensitive than usual in people with IBS. The normal movement of food and gas through the colon causes pain, intestinal spasms and an irregular pattern of bowel movements.

In the past, it was thought that stress might cause IBS. That is no longer the case. Stress does not cause IBS, but stress can increase the symptoms, especially pain.

IBS has been called irritable colon, spastic colon, mucous colitis and functional bowel disease.