What Causes IBD

Key points

  • Inflammatory bowel disease (IBD) triggers the body's immune system to mistakenly attack healthy bowel cells.
  • This causes problems in the intestines, causing life-long disease.
  • IBD appears to result from interactions between genetics and the environment that trigger an immune response.
Illustration of a giant stomach growing out of the ground with three doctors examining it, one on a ladder.

Immune system dysfunction

Inflammatory bowel disease (IBD) refers to a group of lifelong diseases affecting your intestines.

Illustration of a medical team examining a gastrointestinal tract.
The cause of IBD is unclear, but it creates problems with immune function.

IBD causes the body's natural defenses (the immune system) to mistakenly attack healthy bowel cells.

Technically, IBD belongs to the group of diseases called immune-mediated inflammatory diseases.1

  • These are a type of autoimmune disease in which autoantibodies are not detected in common laboratory tests.
  • An autoantibody is a special kind of protein made by the immune system that attacks the body's own proteins.

Although the cause of IBD is complicated and not always clear, scientists have identified some patterns.

Triggers of IBD

A person may develop IBD due to interactions between genetics and the environment, which triggers an immune response.

Genetic factors

A person's genes can affect a person's body (biology), including:

  • The bacterial balance in the gut.
  • How the immune system responds to infections.
  • How the body responds to events that cause inflammation.

More than 200 genetic mutations may play a role in developing IBD.2 Sharing genes with someone—like a parent, sibling or child—that already has IBD can also increase risk.

Environmental factors: IBD and industrialization

Around the world, the number of people with IBD is rising. Risk for IBD increases as:345

  • Countries become industrialized.
  • Individuals—and particularly their children—immigrate to industrialized countries.

Lifestyles in industrialized countries

Industrialized environments lead to lifestyles that are linked to both increased risk of IBD, and changes in the balance of bacteria in the gut. Examples include2:

  • Eating more ultra-processed food.
  • Using oral contraceptives (birth control).
  • Taking non-steroidal anti-inflammatory drugs (NSAIDs), like ibuprofen (Advil, Motrin) and naproxen sodium (Aleve), among others.
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Content Source:
National Center for Chronic Disease Prevention and Health Promotion
  1. McInnes IB, Gravallese EM. Immune-mediated inflammatory disease therapeutics: past, present and future. Nat Rev Immunol. 2021;21(10):680-686. doi:10.1038/s41577-021-00603-1
  2. Flynn S, Eisenstein S. Inflammatory Bowel Disease Presentation and Diagnosis. Surg Clin North Am. 2019;99(6):1051-1062. doi:10.1016/j.suc.2019.08.001
  3. Ng SC, Shi HY, Hamidi N, et al. Worldwide incidence and prevalence of inflammatory bowel disease in the 21st century: a systematic review of population-based studies. Lancet. 2017;390(5):1345-1353.e4. doi:10.1053/j.gastro.2019.01.002
  4. Ananthakrishnan AN, Kaplan GG, Ng SC. Changing Global Epidemiology of Inflammatory Bowel Diseases: Sustaining health care delivery into the 21st century. Clin Gastroenterol Hepatol. 2020;18(6):1252-1260. doi:10.1016/j.cgh.2020.01.028
  5. Molodecky NA, Soon IS, Rabi DM, et al. Increasing incidence and prevalence of the inflammatory bowel diseases with time, based on systematic review. Gastroenterology. 2012;142(1):46-54.e42. doi:10.1053/j.gastro.2011.10.001