Association between periodontitis and depression: A two-sample bidirectional Mendelian randomization study

Abstract

Abstract Background and aims: Emerging studies have identified a possible link between periodontitis and depression, but evidence regarding a causal association between periodontitis and the risk of depression is sparse and conflicting. The aim of this study was to assess the bidirectional relationship between periodontitis and depression using Mendelian randomization (MR) methodology. Methods: The MR study was based on summary statistics for periodontitis and depression from different genome-wide association studies. We used eight independent genetic instruments for periodontitis and 90 for depression. Estimates for the association in both directions were combined using the inverse variance weighted (IVW) method, and several complementary methods were applied Results: Standard IVW analyses showed no causal effect of genetically predicted periodontitis on depression (odds ratio [OR] 1.02, 95% confidence interval [CI] 0.99-1.05; p = 0.193) or vice versa (OR 1.04, 95% CI 0.91-1.20; p = 0.570). The results were robust in complementary analyses. No horizontal pleiotropy was detected via MR-Egger regression or in MR pleiotropy residual sum and outlier analyses. Conclusions: The present study provides evidence that periodontitis and depression may not be mutually reinforcing.