Parkinson's disease and Major depressive disorder: a bidirectional Mendelian randomization study

Background: A substantial gap in knowledge exists regarding the causal relationship between Parkinson’s disease and major depressive disorder.Objective: A bidirectional Mendelian randomization analysis was conducted to investigate the causal relationship between major depression and Parkinson's disease. Methods: Pooled data from the Genome-Wide Association Study (GWAS) was used to obtain information on major depressive disorder (MDD) and Parkinson's disease (PD). single nucleotide polymorphisms (SNPs) were used as instrumental variables. Two-sample bidirectional Mendelian randomization analysis was used to examine causal associations between major depressive disorder (MDD) and Parkinson's disease (PD). The primary method used for this Mendelian randomization (MR) analysis was the inverse variance weighting (IVW) method. Sensitivity analyses, including Cochran's Q test, the MR Egger intercept, and the leave-one-out method, were also performed. Results: The results did not support a causal relationship in any direction between MDD and PD. When MDD was used as an exposure factor, IVW analysis indicated that MDD did not lead to a modified risk of developing PD (OR=1.02, 95%CI: 0.78-1.34, P=0.89>0.05). Likewise, when PD was used as an exposure factor, IVW showed that PD was not associated with an altered risk of developing major depressive disorder (OR=0.99, 95%CI: 0.97~1.01, P=0.27>0.05). Conclusion: This study’s findings do not provide evidence for a causal relationship between Parkinson's disease and major depressive disorder.