What risk factors are associated with inflammatory bowel disease? Original paper

In this umbrella review of 80 meta-analyses, smoking, asthma, and H. pylori had the strongest associations with inflammatory bowel disease.

This Study Summary was published on June 12, 2025.

The study

One hundred ninety-one (191) risk factors were analyzed, and 62 negative associations and 30 favorable associations with diagnosed cases of inflammatory bowel disease were found.

The following risk factors had moderate-quality evidence for increasing the risk of ulcerative colitis and/or Crohn’s disease:

  • Smoking (+61%, 53 studies)
  • Asthma (+30%–31%, 15 to 16 studies)
  • Appendix removal (+128%, 6 studies)
  • Autism spectrum disorder (+57%, 6 studies)
  • Hidradenitis suppurativa (a skin condition with painful, swollen lumps) (+56%–125%, 3 to 5 studies)

The following risk factors had moderate-quality evidence for decreasing the risk of ulcerative colitis and/or Crohn’s disease:

  • H. pylori infection (−58%, 19 studies)
  • Having access to a toilet (−27%, 9 studies)
  • Higher BMI (−24%, 5 studies)
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The results

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    This Study Summary was published on June 12, 2025.