The cause of Crohn’s disease (CD) is unknown. The disease seems to occur equally as often in men as it does in women. However, certain factors appear to be related to the potential for developing CD. These factors include:

• Heredity. CD appears to run in families. Approximately 20 percent of patients with CD have a blood relative with some form of inflammatory bowel disease, according to the National Institutes of Health.
  
  
• Age. Young people, especially those between the ages of 15 and 35, are more likely to develop CD, although CD may also occur in older or younger populations. According to the Crohn's & Colitis Foundation of America, an estimated 100,000 CD patients are children under the age of 18.
  
  
• Race and ethnicity. Whites have a higher risk of developing CD than non-whites. The risk of the disease is greater for people with a Jewish ethnic background (especially those of European descent) than other ethnic groups.
  
  
• Environment. CD appears to be a disease of the developed world, occurring primarily in North America and Europe. It is unclear whether lifestyle (e.g., diet) or possible toxic exposure (e.g., pollutants) in these areas of the world may be related to CD. The risk of CD also appears to increase for those living in urban areas and in northern climates.
  
  
• Cigarette smoking. People who smoke (especially female smokers) are more likely to develop CD than non-smokers. In addition, patients with CD who smoke are more likely to have an aggressive form of the disease. It has been suggested that smoking may be related to CD because it can decrease blood flow to the intestines and cause immune system changes.