Causal associations between genetically determined common psychiatric disorders and the risk of falls: evidence from Mendelian randomization.

Background: The causal associations between psychiatric disorders and falls risk remains uncertain. Consequently, this study aimed to explore the causal relationship between genetically determined three common psychiatric disorders and the risk of falls based on Mendelian randomization (MR).

Methods: The genome-wide association study (GWAS) data for schizophrenia (SCZ) (N = 320,404), major depressive disorder (MDD) (N = 480,359), and Alzheimer's disease (AD) (N = 63,926) were obtained as exposures. The GWAS data for falls risk (N = 451,179) was obtained as outcome. Univariate Mendelian randomization (UVMR) was used to evaluate the direct causal relationship between SCZ, MDD, AD, and risk of falls. Inverse variance weighting (IVW) was used as the primary analysis method. Sensitivity analysis was performed to assess the validity of the casualty. Multivariate Mendelian randomization (MVMR) analysis was conducted after adjusting body mass index and smoking initiation. Mediating MR was conducted to calculate the mediating effects of potential intermediaries.

Results: UVMR analysis showed that SCZ (OR 1.02, 95% CI 1.01-1.04, p = 8.03E-03) and MDD (OR 1.15, 95% CI 1.08-1.22, p = 1.38E-05) were positively associated with the risk of falls. Sensitivity analysis results were reliable and robust. MVMR results indicated that the relationship between MDD and SCZ and falls risk remained significant. Mediating MR results demonstrated that smoking initiation mediated partial causal effect of SCZ (0.65%, P = 0.03) and MDD (14.82%, P = 2.02E-03) on risk of falls.

Conclusions: This study provides genetic evidence for a causal relationship of individuals with SCZ and MDD on an increased risk of falls. Healthcare providers should be aware of the risk of falls in MDD and SCZ patients and develop strategies accordingly.