Causes of Crohn’s Disease



IBD affects an estimated one in 100 Americans. Unfortunately, the causes of Crohn’s disease are not yet well understood. That’s why the Crohn’s & Colitis Foundation is working to further research about Crohn’s disease and find a cure.



Here’s what we do know:

  • Men and women are equally likely to be affected.

  • The disease can occur at any age, but Crohn’s disease is most prevalent in adolescents and adults between the ages of 15 and 35.

  • Diet and stress may aggravate Crohn’s disease, but do not cause the disease.

  • Recent research suggests hereditary, genetic, and environmental factors contribute to Crohn’s disease development.

Crohn’s Disease and the Immune System

A person’s immune system usually attacks and kills foreign invaders like bacteria, viruses, fungi, and other microorganisms. During a normal immune response, cells travel out of the blood to the intestines and produce inflammation. Under normal circumstances, harmless bacteria that’s present in the GI tract are protected from an immune system attack.


In people with IBD:

  • These harmless bacteria are mistaken for foreign invaders and the immune system mounts a response.

  • The inflammation caused by the immune response does not go away. This leads to chronic inflammation, ulceration, thickening of the intestinal wall, and, eventually, symptoms of Crohn’s disease.

Genetic Factors

Crohn’s disease tends to run in families, so if you or a close relative has the disease, your family members have an increased chance of developing Crohn’s. Studies have shown that between 5% and 20% of people with IBD have a first-degree relative, such as a parent, child, or sibling, who also has one of the diseases. The genetic risk is greater with Crohn’s disease than ulcerative colitis.

Other Genetic Risk Factors

  • The risk of Crohn’s disease or ulcerative colitis is substantially higher when both parents have IBD.

  • The disease is most common among people of eastern European backgrounds, including Jews of European descent.

  • There have been an increased number of cases reported in African-American populations in recent years.

Environmental Factors

Where you live appears to play a role in the development of Crohn’s disease.

Here’s where Crohn’s disease is more common:

  • Developed countries, rather than undeveloped countries

  • Urban cities and towns, rather than rural areas

  • Northern climates, rather than southern climates

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