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Who Gets IBD?

IBD tends to run in families, showing that genes definitely play a role in the cause of IBD. Studies have shown that almost 1 in 4 patients may have a close relative with IBD. If a person has a relative with Crohn’s disease, his or her risk is about 10 times greater than that of the general population. If that relative is a parent, a brother or a sister, the risk is 30 times greater. The lifetime risk for a first degree relative of someone with Crohn’s disease is about 5% (1 in 20).

In recent years, much of the IBD research has been focused on trying to find a link to specific genes that control the transmission of this disease. An important breakthrough was achieved when the first gene for Crohn’s disease was identified by a team of IBD researchers. The researchers were able to isolate a mutation in a gene known as NOD2. This mutation, which limits the ability to recognize bacteria as dangerous or harmful, occurs frequently in Crohn’s patients. Our McGill IBD research team very recently discovered that vitamin D can improve the function of the NOD2 gene.

The data further suggests that more than one gene may be involved in the cause of IBD. The advances made in genetics in recent years have lead researchers to be hopeful of isolating these additional genes and discovering a cure. You can read more about the research conducted by McGill IBD researchers.

There is no evidence to show that anxiety or tension is responsible for IBD. No single personality type is more prone to develop IBD than others, and there is no evidence that depression or poor emotional control causes the disease.

Race and Ethnicity

It is recognized that IBD affects certain ethnic groups more than others. For example, Jews of European descent (Ashkenazis) are four times more likely to develop IBD than the general population. IBD has long been thought of as a disease predominantly affecting Caucasians. However, there has been a steady increase in reported cases of both Crohn’s disease and ulcerative colitis among many other ethnic groups as well. The breakdown of the population of patients followed McGill IBD Research Group is as follows:

  • African3.2%
  • Asian3.5%
  • Caucasian45.1%
  • French Canadian21.5%
  • Jewish Ashkenazi18.6%
  • Jewish Sephardic3.0%
  • Latin American0.9%
  • Middle Eastern4.1%


Interestingly, whereas ulcerative colitis is found in most parts of the world, Crohn’s disease is primarily found in regions of the world distant from the equator (see Figure 3B), principally in North America and Europe. Crohn’s disease and ulcerative colitis are reported to be more common in urban than in rural areas and in northern than in southern climates. Also, the incidence of disease increases when specific groups of people move from underdeveloped to developed countries. Our recent McGill IBD research breakthrough suggests that lack of sunshine and vitamin D may play a role.



Figure 3B: Geographical distribution of Crohn’s disease.<br /> Crohn’s disease and ulcerative colitis have their highest prevalence in Western industrialized countries of Europe and North America. Intermediate prevalence is found in developing countries including post World War II Japan, Korea, Hong Kong, South Africa, and Israel. As new areas assume Western cultural practices, increased prevalence of ulcerative colitis usually is found approximately one decade before the observed increase in Crohn’s disease.<br /> The influence of environmental factors is also demonstrated by changes in the incidence and prevalence of IBD when populations move from one area to another. For example, Japanese immigrants to Vancouver have an increased prevalence of disease in the first generation born in North America and Eastern European Jewish settlers in Israel have decreased frequencies of disease in their offspring in Israel. Note that areas of low prevalence of IBD have the highest frequency of indigenous intestinal infections, including helminthic infestations.