Estimating the causal effect of air pollution on mental disorders: A two-sample Mendelian randomization study

Background: Observational studies have reported a link between particulate matter 2.5 (PM2.5) and the risk of mental disorders; however, the causality is unclear. Methods: Using publicly available genome-wide association studies, we conducted a two-sample Mendelian randomization (MR) study to assess the causal relationship between PM2.5 and six mental disorders: attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), bipolar disorder (BD), major depressive disorder (MDD), schizophrenia (SCZ), and anxiety disorder (ANX). The inversevariance weighting method was used as the main method for estimating causal effects. MR-Egger, weighted median, simple mode, weighted mode, and MR-PRESSO were applied as supplementary analyses. Results: Using the inverse-variance weighting method, genetically predicted PM2.5 exposure increased the risk of ADHD (odds ratio [OR] = 1.52, 95% confidence interval [CI] = 1.16 to 1.99, p = 0.002), ANX (OR = 2.96, 95% CI = 1.29 to 6.81, p = 0.01), and SCZ (OR = 2.21, 95% CI = 1.40 to 3.47, p = 0.001). However, there was no evidence to suggest that genetically predicted exposure to PM2.5 increased the risk of the other three mental disorders (p > 0.05). Conclusions: The present findings enhance our understanding of the role of PM2.5 exposure on ADHD, ANX, and SCZ risk. It may be necessary to search for novel components with neuroprotective effects to provide new preventive and therapeutic strategies for PM2.5-induced brain damage. (c) 2024 Published by Elsevier Ltd on behalf of Tsinghua University Press. This is an open access article