Association between epigenetic age acceleration and psychiatric disorders: a bidirectional Mendelian randomization study

Aging is a complex process influenced by genetic, environmental, and psychiatric factors. Recent evidence suggests that epigenetic age acceleration (EAA), a biomarker of biological aging, may be linked to psychiatric disorders, yet the causal direction remains unclear. This study employed a bidirectional two-sample Mendelian randomization (MR) analysis to explore the causal relationships between EAA (IEAA, HannumAA, GrimAA, PhenoAA) and ten psychiatric disorders. Genome-wide association study (GWAS) summary statistics from large European ancestry cohorts were used, and sensitivity analyses were conducted to ensure robustness. Forward MR analysis demonstrated that PhenoAge acceleration (PhenoAA) significantly increased the risk of attention-deficit hyperactivity disorder (ADHD) (OR = 1.043, P = 0.004), suggesting that cumulative biological aging may contribute to neurodevelopmental vulnerabilities. Conversely, Hannum age acceleration (HannumAA) was associated with a protective effect against obsessive-compulsive disorder (OCD) (OR = 0.904, P = 0.004). Reverse MR analysis revealed that autism spectrum disorder (ASD) was linked to a decrease in intrinsic epigenetic age acceleration (IEAA) (OR = 0.811, P = 0.027), while major depressive disorder (MDD) significantly increased both HannumAA (OR = 1.318, P = 0.005) and IEAA (OR = 1.226, P = 0.049). These findings suggest that psychiatric conditions may both influence and be influenced by biological aging processes. This study reveals a bidirectional link between psychiatric disorders and biological aging, showing that early-life mental health conditions may accelerate epigenetic aging and increase age-related disease risk. As psychiatric disorders are recognized as aging risk factors, these findings highlight the need for research on aging-targeted interventions in psychiatric populations.