Background. Previous observational evidence has suggested an association between smoking and inflammatory bowel disease (IBD).

Methods. We used observational techniques followed by Mendelian randomisation (MR) to explore if smoking is a causal factor in the development of IBD and its subtypes.

Results. In those who have ever smoked, we observed increased risk of IBD, and, in current smokers, we observed increased risk of Crohn’s disease and decreased risk of Ulcerative Colitis. However, our MR analyses found little evidence that smoking affects the development of IBD.

Conclusion. Overall, our results suggest that smoking does not causally influence the risk of IBD.
Original languageEnglish
Number of pages7
JournalCrohn's and Colitis 360
Issue number1
Publication statusPublished - 12 Mar 2020

Structured keywords

  • Physical and Mental Health
  • Tobacco and Alcohol


  • smoking
  • inflammatory bowel disease
  • Mendelian randomisation
  • UK Biobank

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