What causes Crohn’s?

The exact causes of Crohn’s disease aren’t known. Diet and stress were once believed to be responsible. However, we now understand that the causes of this condition are much more complex.

Research suggests that it’s an interaction of factors, that a malfunctioning immune response, genetics, and the environment (including microorganisms and food) likely all play a role in the development of the disease.

Immune system

A main characteristic of Crohn’s disease is chronic inflammation. Inflammation is the result of a working immune system and its response to outside invaders such as viruses, bacteria, parasites, and anything the body labels as foreign.

Some researchers believe that Crohn’s disease may start as a normal response to an outside invader. Then the immune system fails to shut off after the problem is resolved, resulting in chronic inflammation.

Another observation is that the lining of the intestinal tract is abnormal when there is excess inflammation. These changes seem to interfere with how the immune system functions. When your immune system attacks normal parts of your body, it’s called an autoimmune disorder.

This abnormal lining may also have a role in the body’s overreaction to other things in the environment. The immune system may be activated by mistaking certain protein or carbohydrate structures on some foods for an invading organism or some of your body’s own tissue.


Over 160 gene locations have been identified in relationship to IBD (inflammatory bowel disease). There is also an overlap in genetic changes between individuals with Crohn’s disease and those with ulcerative colitis. Scientists are convinced that genetics plays a large role in the development of Crohn’s disease.

The Crohn’s and Colitis Foundation of America (CCFA) says that, according to studies, 5 to 20 percent of people with Crohn’s disease have a first-degree relative (a parent, child, or sibling) with the disease.

Crohn’s disease is more common in people of Northern European and Anglo-Saxon descent and is many times more common in Jewish people of European descent, also called Ashkenazi Jews, than in the rest of the population.

Crohn’s occurs much less frequently in central and southern Europe, and less still in South America, Asia, and Africa.

It’s beginning to occur more frequently in blacks and Latin Americans living in North America. This and other evidence strongly suggest that heredity alone isn’t always responsible.


Crohn’s is more common in industrialized nations and in urban areas. People who live in northern climates seem to have a greater risk of developing the disease. This suggests that environmental factors such as pollution, stressors to the immune system, and a Western diet may play a role.

Researchers believe that when particular genes interact with certain things in the environment, the likelihood for developing Crohn’s disease goes up.

Cigarette smoking

According to the Journal of Crohn’s and Colitis, research suggests that people who smoke are more likely to develop Crohn’s disease than nonsmokers. The increased risk is likely due to the interaction between smoking and the immune system, along with a variety of other genetic and environmental factors.

However, if you have Crohn’s and smoke, you are more likely to have more frequent flares, have more challenges with medication, and require surgery.

A 10-year study showed that those with Crohn’s disease who smoked were 29 percent more likely to need surgery than those with Crohn’s who didn’t smoke.

The takeaway

The causes of Crohn’s disease are complex. Given this, there is no one thing a person can do to prevent the disease. The immune system, genetics, and the environment all play a part.

However, understanding the causes can help scientists target new treatments and improve the course of the disease.