Are you at risk?

Canada has one of the highest rates of Crohn's disease and ulcerative colitis – the two main forms of inflammatory bowel disease (IBD) – in the world. Since the 20th century, the number of diagnoses of ulcerative colitis and Crohn's disease has increased dramatically in Canada. IBD is more common in industrialized countries, urban areas, and temperate regions.

In 2021, more than 300,000 Canadians are believed to be living with IBD. By 2030, this figure is expected to reach 403,000 (or 1 in 100 people).

Crohn's disease and colitis can be diagnosed at any age, but they most commonly appear before the age of 30. The number of cases of Crohn's disease in children under the age of 10 in Canada has almost doubled since 1995. IBD affects people of both sexes equally.

Crohn's disease and colitis can affect people of all races and ethnic groups. However, the Ashkenazi Jewish (European) population and some South Asian immigrant populations have been shown to have more cases of inflammatory bowel disease.

The causes of IBD are very complex. They are believed to be due to a genetic tendency (predisposition) and an environmental trigger that combine to cause intestinal inflammation. Inappropriate and untimely activation of the immune response would lead to a chronic (permanent) disorder that manifests as Crohn's disease or ulcerative colitis.

Understanding the biological factors underlying IBD is essential to developing new strategies to improve the quality of life of people living with the disease. This includes improving treatment approaches, exploring possible avenues for curbing the disease and targeting prevention approaches.

Below is more information about genetic, microbiotic and environmental factors that may contribute to the development of IBD.


The impact of genetics on IBD has long been recognized. Previous twin studies show that identical twins are more likely to both have Crohn's disease or ulcerative colitis than non-identical twins.

Genetic analyzes of large regions of the human genome have identified more than 200 genetic mutations associated with the onset of Crohn's disease and ulcerative colitis.

In many cases, these genetic mutations are also linked to other autoimmune diseases including type 1 diabetes, celiac disease, rheumatoid arthritis, ankylosing spondylitis and psoriasis.

Identifying the proteins produced by these genetic markers paints an accurate picture of the critical link between the gut's immune response and the 100 trillion microbes that live there.


It is possible that changes in the gut microbiome trigger immune responses that cause abnormal inflammation. Because people with IBD are usually the focus of attention after the disease has manifested, it is not yet clear whether changes in the microbiome and immune responses are a cause or an effect of the disease. disease.

It has been suggested that antibiotics, which can alter the gut microbiome even long after the patient has stopped taking them, may cause the onset of IBD.

Much more needs to be done to understand the exact causes of changes in the microbiome and the changes that seem most involved in triggering the disease, so that it is possible to develop effective treatments to prevent or cure them. IBD.

Environmental factors

Numerous research studies have identified environmental factors that play a key role in triggering the onset of IBD. These environmental determinants include both risk factors and protective factors which are described in more detail below.

Crohn's disease

Risk factors

Fumeur actuel icon

Current smoker

Ancien fumeur icon

Former Smoker

Infection à entérobactéries icon

Enterobacterial infection

Aliments qui favorisent l'inflammation icon

Foods that promote inflammation

Pollution atmosphérique icon

Atmospheric pollution

Anti-inflammatoires non stéroïdiens icon

Nonsteroidal anti-inflammatory drugs

Déménagement dans une région à prévalence accrue de la maladie icon

Moving to an area with increased disease prevalence

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Hormone drug

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Stress and depression

Illustration d'une personne atteinte d'une MII

Protective factors

Jamais fumé icon


H. Pylori (Infection bactérienne)

H. Pylori (Bacterial Infection)

Aliments anti-inflammatoires icon

Anti-inflammatory foods

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Vitamin D

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Natural breastfeeding

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Presence of pets during childhood

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Vie en région rurale

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Physical activity

Image reference. 2018 Impact of inflammatory bowel disease in Canada Report.

Hygiene hypothesis

Some have argued that the immune systems of children growing up in relatively sterile environments – without adequate exposure to microbes – were not well prepared to deal with microorganisms. These children then develop an abnormal immune response that attacks their organs later in life when they are exposed to harmful microorganisms.

Research supporting this hypothesis shows that Crohn's disease and ulcerative colitis are less likely to occur in people who: lived with pets as children; grow up on a farm or in a rural setting; have a large family; or drink unpasteurized milk.

Recent studies have also demonstrated that susceptibility to IBD may be due to early exposures altering the composition of the gut microbiome, including the loss of helpful microorganisms that may benefit the immune system. IBD is more likely to develop in people who were exposed to antibiotics during their first year of life and also in people who were not breastfed. Antibiotics and breastfeeding have a significant impact on microbiome diversity in children.

People with a history of infectious gastroenteritis are more likely to be diagnosed with Crohn's disease or ulcerative colitis, especially in cases of IBD that begin in childhood.


Dietary factors can have a significant impact on the gut microbiome. The results of some studies suggest that a Western diet, a diet higher in fat and refined sugars and lower in dietary fiber, changes the microbiome of our gut.

Processed foods and the ubiquitous fast foods of the Western diet may also be factors contributing to the onset of IBD. The association between junk food consumption and IBD may be direct, through exposure to fatty foods and food additives, or indirect, through lifestyle factors such as insufficient physical activity.

Other environmental factors

Several other environmental factors can influence the development of IBD in Canadians, including the following:

  • Smoking increases the risk of developing Crohn's disease in adults. However, adults who quit smoking are at increased risk of ulcerative colitis.
  • Oral contraceptives increase the risk of Crohn's disease in women who smoke.
  • Nonsteroidal anti-inflammatory drugs also trigger IBD.
  • Appendicitis diagnosed before the age of ten protects against ulcerative colitis.
  • A lack of vitamin D due to reduced exposure to sunlight can increase the risk of developing IBD. Vitamin D is involved in the regulation of the immune system and a deficiency of this vitamin has been linked to an increased risk of IBD.
  • Air pollution can increase the risk of developing Crohn's disease in children and young adults because it alters the gut microbiome.

Many research projects funded by Crohn's and Colitis Canada are investigating the causes of these diseases – visit the Research page to learn more.

Have you recently been diagnosed with Crohn's disease or colitis?

If you have recently been diagnosed with Crohn's disease or colitis, visit our Newly Diagnosed page for more information and resources.

Strengthen your knowledge about living with Crohn's disease or colitis

Visit the Living with Crohn's or Colitis section of our website to learn more about diet and nutrition for people with IBD, treatment options, symptom management, and more essentials.

Find a community near you

Your local Crohn's and Colitis Canada chapter is a solid source of information and support. Through our educational programs, presentations and discussions, people can find resources that will help them cope with their Crohn's disease or colitis and meet others with these conditions.

Visit our Find My Community page to locate the section closest to you. It is in your best interest to become active and informed!

  • Canada has among the highest incidence rates of Crohn's and colitis in the world.
  • 1 in 140 Canadians lives with Crohn’s or colitis.
  • Families new to Canada are developing these diseases for the first time.
  • Incidence of Crohn’s in Canadian kids under 10 has doubled since 1995.
  • People are most commonly diagnosed before age 30.