What is the cause of Crohn’s disease?

Despite extensive and continuing research the cause of Crohn’s Disease is still unknown. However, there are a number of predisposing factors, which may play a part in the development of the disease:

• Infection
Crohn’s Disease is NOT contagious. Husbands and wives of patients with Crohn’s are not at any increased risk of getting the condition.

Crohns disease may arise after certain infections particularly gastroenteritis. It appears that in some way infections in the gut may trigger an immune response. Not only against the bacteria causing the infection but also against other harmless bacteria which live in all our intestines.

• Immunological Factors
The body's own defence mechanism (the immune system), which provides protection against infection, is activated by intsetinal bacteria in Crohn’s Disease and may be involved in causing damage to the mucosa. Many drugs used to control Crohn’s Disease affect this system. However, it is likely that immunological changes are produced after the disease has started rather than causing it.

• Dietary Factors
Some patients find that their Crohn’s Disease is better if they avoid certain foods such as wheat, yeast or milk. However, many other patients with the disease are able to eat these foods. It is possible that the breakdown of certain foods (perhaps by bacteria) in the large intestine plays a part in Crohn’s Disease.

• Psychological factors
Although not a proven cause, periods of emotional stress have been linked with flare-ups of the disease.

• Smoking
Crohn’s disease is much worse in people who smoke. They are more likely to need surgery and suffer more frequent relapses. The reason that smoking makes Crohn’s disease worse is poorly understood.


• Genetics and Heredity
The occurrence of Crohn’s Disease in more than one member of a family is more common than would be expected, thus, there is a hereditary tendency. The risk to family members varies considerably between studies but is generally highest when a brother or sister is affected. Studies on twins have also shown a higher incidence amongst identical compared to non-identical twins.

Extensive work is being carried out in this area in order that genetic counselling may be of benefit. Data from studies already carried out suggests that the majority of any class of relatives will not show signs of the disease.