Mendelian randomization study finds no causal link between inflammatory bowel disease and cirrhosis

While some observational research has pointed to a connection between inflammatory bowel disease and increased cirrhosis risk, it has been difficult to determine if this is a genuine cause-and-effect relationship. The challenge lies in separating actual causation from confounding factors that might influence both conditions. In this study, we turned to Mendelian randomization (MR) - a method that uses genetic variations as natural experiments - to investigate whether inflammatory bowel disease (IBD) truly causes cirrhosis. We performed a two-sample MR analysis. Genetic instruments for IBD were obtained from the IBD Genetics Consortium. Cirrhosis outcome data were sourced from both the FinnGen consortium and the UK Biobank, with summary statistics combined via fixed-effects meta-analysis. Methods included inverse-variance weighted, MR-Egger, weighted median, and sensitivity analyses (including Cochran Q test, MR-Egger intercept test, and leave-one-out analysis). The evidence from our MR analysis does not support a causal effect of IBD on cirrhosis risk. Our main analysis using inverse-variance weighted showed an odds ratio of 1.02 (95% confidence interval = 0.97-1.07, P = .42), indicating no significant association. Other methods told the same story, and our sensitivity analyses revealed no concerning heterogeneity or pleiotropy that might undermine these results. Put simply, our findings suggest that IBD does not directly cause cirrhosis. The associations seen in previous observational studies were likely driven by other factors that affect both conditions, rather than a direct biological pathway from IBD to liver damage.