Doctors do not know the exact causes of inflammatory bowel disease. IBD appears to be due to an interaction of many complex factors including genetics, impaired immune system response, and environmental triggers. The result is an abnormal immune system reaction, which in turn causes an inflammatory response in the body’s intestinal regions.
The Inflammatory Response
An inflammatory response occurs when the body tries to protect itself from what it perceives as invasion by a foreign substance (antigen). Antigens may be viruses, bacteria, or other harmful substances. In Crohn’s disease and ulcerative colitis, the body mistakenly targets harmless substances (food, beneficial bacteria, or the intestinal tissue itself) as harmful. To fight infection, the body releases various chemicals and white blood cells, which in turn produce byproducts that cause chronic inflammation in the intestinal lining. Over time, the inflammation damages and permanently changes the intestinal lining.
Although the exact causes of inflammatory bowel disease are not yet known, genetic factors certainly play some role. Between 10 - 20% of people with ulcerative colitis have family members with the disease. Several identified genes and chromosome locations play a role in the development of ulcerative colitis, Crohn's disease, or both. Genetic factors appear to be more important in Crohn's disease, although there is evidence that both conditions have some genetic defects in common.
Some studies have reported that children with IBD may have had more and earlier childhood infections. The measles virus has been of particular interest. However, according to the U.S. Centers for Disease Control and Prevention, and many studies, the measles virus does not cause Crohn’s or IBD. In addition, studies conclusively report that the measles, mumps, and rubella (MMR) vaccine does not cause Crohn’s disease, ulcerative colitis or, for that matter, autism.
Inflammatory bowel disease is much more prevalent in industrialized nations and in higher-income groups. However, there is no strong evidence that diet or particular types of food cause Crohn’s disease or ulcerative colitis.
Review Date: 09/28/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.