Causes and Risk Factors for Crohn's Disease

The cause for Crohn's disease is unknown, but researchers are studying several possibilities. The most widely-accepted theory centers on the immune system, which does not appear to function properly in patients who have the disorder.

When certain usually benign substances (e.g., foods, bacteria) enter the intestinal tract, the immune system mistakenly identifies them as harmful substances and tries to destroy them. White blood cells, which fight foreign substances in the body, accumulate and eventually cause severe inflammation and lead to ulcers and bowel problems. In other cases, the immune system overreacts to antigens (e.g., viruses, bacteria) in the digestive system and the ongoing process causes inflammation.

Heredity may play a large role in the development of Crohn's disease. A genetic mutation (e.g., Nod2 gene, CARD15 gene) appears to influence the immune system, causing it to malfunction. Because Crohn's disease runs in families, this defective gene may be passed from one generation to the next.

The following factors may increase the risk for Crohn's disease:

  • Family history (appears to be inherited in many cases)
  • Environment (more common in urban areas and developed countries)
  • Ethnicity (occurs more often in the United States and Europe, particularly in Caucasians and people of Jewish descent)
  • Age (commonly develops between the ages of 15 and 35)
  • Smoking

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 28 Feb 2008

Last Modified: 10 Sep 2015