biostudies-literatureUnknown8(1)Freuer DEmerging evidence from observational studies suggests an increased risk of Parkinson's disease (PD) in patients with inflammatory bowel disease (IBD). However, to date it is not clear whether a causal relationship exists. To investigate whether IBD is causally related to PD, a two-sample Mendelian randomization study was carried out. Independent genetic instruments from the largest available genome-wide association study (GWAS) for IBD (7045 cases, 456,327 controls) including European participants were used to investigate the association with PD (56,306 cases; 1.4 million controls). The results were validated by using a second IBD sample (12,882 cases; 21,770 controls) including the main subtypes ulcerative colitis (UC; 6968 cases; 20,464 controls) and Crohn's disease (CD; 5956 cases; 14,9NPJ Parkinson's disease55https://www.ebi.ac.uk/biostudies/studies/S-EPMC9085764biostudies-literatureAssociation between inflammatory bowel disease and Parkinson's disease: A Mendelian randomization study.PMC9085764Meisinger CFreuer DfalseAssociation between inflammatory bowel disease and Parkinson's disease: A Mendelian randomization study.Emerging evidence from observational studies suggests an increased risk of Parkinson's disease (PD) in patients with inflammatory bowel disease (IBD). However, to date it is not clear whether a causal relationship exists. To investigate whether IBD is causally related to PD, a two-sample Mendelian randomization study was carried out. Independent genetic instruments from the largest available genome-wide association study (GWAS) for IBD (7045 cases, 456,327 controls) including European participants were used to investigate the association with PD (56,306 cases; 1.4 million controls). The results were validated by using a second IBD sample (12,882 cases; 21,770 controls) including the main subtypes ulcerative colitis (UC; 6968 cases; 20,464 controls) and Crohn's disease (CD; 5956 cases; 14,92022-01-01T00:00:00Z2022 May2026-03-27T15:18:03.771Z2025-04-04T19:09:55.994ZS-EPMC90857643553450710.1038/s41531-022-00318-7