What is Irritable Bowel Syndrome?
This is a disorder in which the colon does not function properly. There is no known underlying medical cause. This condition usually begins in the late teens or early 20s.

Symptoms
Abdominal pain -- crampy lower abdomen
Abdominal pain relieved by bowel movements
Increased stool when abdominal pain starts
Diarrhea or Constipation or fluctuation between both of these
Abdominal Bloating
Anxiety may be present
Depression may be present

Cause
A genetic predisopsition
Psychogenic factors - anxiety plays a major role in the development of IBS. The patients are often tense, conscientious individuals who worry excessively.
Diet - at times certain substances like milk and barley products
Infections - bacterial or amoebic infection
Drugs - abuse of laxatives, antibiotics, and digoxin