The gut-lung axis: Mendelian randomization identifies a causal association between inflammatory bowel disease and interstitial lung disease

Inflammatory bowel disease (IBD), a group of idiopathic inflammatory disorders affecting the gastrointestinal tract, encompasses Crohn's disease (CD) and ulcerative colitis (UC), and is often associated with the development of interstitial lung disease (ILD).1 Although extensive evidence from observational studies suggests a link between these diseases, the causal relationship remains unestablished due to limitations inherent in traditional research methodologies.2,3 Mendelian Randomization (MR), an analytical technique akin to randomized controlled trials (RCTs), utilizes genetic variants from genome-wide association studies (GWAS) as instrumental variables (IVs) to ascertain the causal impact of risk factors (or exposures) on outcomes.