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Irritable bowel syndrome

  • Definition

    Irritable bowel syndrome (IBS) refers to a disorder that involves abdominal pain and cramping, as well as changes in bowel movements.

    It is not the same as inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis.


    Alternative Names

    Spastic colon; Irritable colon; Mucous colitis; Spastic colitis


    Causes, incidence, and risk factors

    There are many possible causes of IBS. For example, there may be a problem with muscles in the intestine, or the intestine may be more sensitive to stretching or movement. There is no problem with the structure of the intestine.

    It is not clear why patients develop IBS, but in some instances, it occurs after an intestinal infection. This is called postinfectious IBS. There may also be other triggers.

    Stress can worsen IBS. The colon is connected to the brain through nerves of the autonomic nervous system. These nerves become more active during times of stress, and can cause the intestines to squeeze or contract more. People with IBS may have a colon that is over-responsive to these nerves.

    IBS can occur at any age, but it often begins in adolescence or early adulthood. It is more common in women. About 1 in 6 people in the U.S. have symptoms of IBS. It is the most common intestinal complaint for which patients are referred to a gastroenterologist.