The causes of inflammatory bowel disease are difficult to pinpoint, but there are some recognized probable risk factors according to health.com:
People who live in developed western countries, like the U.S. and Northern Europe, are more likely to have an inflammatory bowel disease. This could come down to lifestyle choices such as smoking, drinking, a diet of processed foods, or the effects of pollution.
However, less-developed countries, particularly in Asia, are seeing a rise in the number of cases of IBD. This could also be due to the increase of processed foods in worldwide diets or an increase in environmental pollution.