Causality between periodontitis and schizophrenia, bipolar disorder, and major depressive disorder: A mendelian randomization study.

BACKGROUND: Increasing evidence suggests that periodontitis (PD) is epidemiologically associated with mental health. To minimize the influence of confounding factors, we employed Mendelian randomization (MR) as the analytical approach to investigate the potential causal relationships between PD and schizophrenia (SZ), bipolar disorder (BD), and major depressive disorder (MDD). METHODS: 8 single nucleotide polymorphisms (SNPs), sourced from a genome-wide association study (GWAS) of 45,563 individuals were used as instrumental variables for PD. 131, 52 and 0 SNPs were employed from 3 GWASs of SZ, BD and MDD, respectively. We took inverse variance-weighted model as the primary method for causal estimation supplemented by MR-Egger and Weighted-median. Then we conducted sensitivity analysis and leave-one-out analysis. RESULTS: Periodontitis is the risk factor of BD (OR = 1.10; P = 0.0086). However, no significant causal association was observed between PD and SZ (OR = 1.03; P = 0.5045) or MDD (OR = 1.06; P = 0.1089). Neither SZ (OR = 1.01; P = 0.6763), BD (OR = 1.06; P = 0.2070) nor MDD was associated with PD. CONCLUSIONS: Our analysis supports previous epidemiological findings by showing a potential causal association between PD and BD; whereas, no causal link of PD with SZ or MDD, and SZ, BD or MDD with PD. These offers novel concepts for the diagnosis and treatment.