IBS is indeed irritable, often causing a great deal of discomfort and distress. But the good news is that the syndrome does not cause permanent harm to the intestines, it doesn't lead to intestinal bleeding and it doesn't cause cancer or inflammatory bowel diseases (such as Crohn's disease or ulcerative colitis). Moreover, if you have IBS, you may not suffer all the time — some people can go for weeks or months with no symptoms. Others may experience symptoms daily. Also, it is possible — by paying attention to the triggers of your symptoms — that you can modify your diet, make lifestyle changes to reduce stress and use medication to reduce these symptoms.
Depression and anxiety disorders can aggravate IBS, and some research indicates that the syndrome may be more common among people who were abused as children. But psychological factors notwithstanding, the symptoms are real and have a physiological basis. While stress may aggravate IBS symptoms, other factors — particularly colon motility and sensitivity of the nerves in the colon — play an important role. (Colon motility — the contraction of intestinal muscles and movement of its contents — is controlled by nerves and hormones.)
While there is no cure, you often can control symptoms through diet, stress management and prescription drugs. IBS is rarely debilitating, but in some cases, it restricts the ability to attend school or social functions, go to work or even travel short distances.
The colon, or large intestine, is about six feet long. Its primary function is to absorb water and salts from digestive products that enter from the small intestine. About two quarts of liquid matter enter the colon from the small intestine each day; it can remain there for days until most of the fluid and salts are absorbed. The leftover matter — the stool — then passes through the colon by a pattern of movements to the left side of the colon, where it is stored until a bowel movement occurs.
Movements of the colon propel the contents slowly back and forth but mainly toward the rectum. A few times each day strong muscle contractions move down the colon pushing fecal material; some of these contractions result in a bowel movement.
IBS changes this process because there is an abnormality in the muscular action. The person with IBS seems to have a colon that is more sensitive and reactive than usual. Otherwise ordinary events (such as eating and distension from gas or other material in the colon) can cause your colon to overreact. Certain medicines and foods, such as chocolate, high-fat foods, milk products or large amounts of alcohol, may trigger attacks. Caffeine can cause loose stools even in some people without the condition, and it is particularly problematic for people with IBS.