DefinitionIrritable bowel syndrome (IBS) refers to a disorder of the lower intestinal tract. It involves abdominal pain and abnormal bowel movements. Emotional stress often makes the symptoms worse.It is not the same as inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis.Alternative NamesNervous indigestion; Spastic colon; Intestinal neurosis; Functional colitis; Irritable colon; Mucous colitis; Laxative colitis; IBSCauses, incidence, and risk factorsIBS involves a combination of abdominal pain and constipation, diarrhea, or an alternating pattern of these problems.There are many possible causes. For example, there may be a problem with muscle movement in the intestine or a lower tolerance for stretching and movement of the intestine. There is no problem