Association of air pollutants with psychiatric disorders: a two-sample Mendelian randomization

The link between air pollution and increased risk of psychiatric disorders has been growing in evidence. However, the causal relationship between air pollution and psychiatric disorders remains poorly understood.

Single-nucleotide polymorphisms associated with air pollutants (including NOx, NO₂, PM_2.5, PM_2.5-10, and PM₁₀) from the UK Biobank were used as instrumental variables. Summary-level data for psychiatric disorders (major depressive disorder, anxiety, bipolar disorder, schizophrenia, post-traumatic stress disorder, attention deficit hyperactivity disorder, autism spectrum disorder, anorexia nervosa, and obsessive-compulsive disorder) were procured from the Psychiatric Genomics Consortium and FinnGen consortium. Two-sample Mendelian randomization (MR) analysis was conducted to analyze the causal associations.

The MR analysis revealed significant associations between certain air pollutants and specific types of psychiatric disorders. The inverse-variance weighted model of preliminary analysis indicated that genetically predicted NO₂ was associated with increased risks of major depressive disorder (odds ratio [OR]: 1.13, 95 % confidence intervals [CI]: 1.00-1.28, P = 0.041), bipolar disorder (OR: 1.26, 95 % CI: 1.00-1.58, P = 0.0497), schizophrenia (OR: 1.57, 95 % CI: 1.23-2.00, P < 0.001), attention deficit hyperactivity disorder (OR: 1.61, 95 % CI: 1.25-2.09, P < 0.001) and autism spectrum disorder (OR: 1.39, 95 % CI: 1.01-1.91, P = 0.044). Genetically predicted PM_2.5 showed a positive association with the risk of major depressive disorder (OR: 1.21, 95 % CI: 1.06-1.39, P = 0.006), bipolar disorder (OR: 1.32, 95 % CI: 1.03-1.69, P = 0.030) and attention deficit hyperactivity disorder (OR: 1.57, 95 % CI: 1.16-2.12, P = 0.004). In addition, our results also indicated that NOx (OR: 1.64, 95 % CI: 1.21-2.21, P = 0.0012) and PM₁₀ (OR: 1.70, 95 % CI: 1.23-2.36, P = 0.0014) could increase the risk of attention deficit hyperactivity disorder.

The MR analysis provides evidence for the causality of different air pollutants on specific psychiatric disorders, underscoring the importance of mitigating air pollution to reduce the risk of psychiatric disorders.