Schizophrenia is characterized by age- and sex-specific effects on epigenetic aging

Schizophrenia (SCZ) is a severe mental illness that is associated with an increased prevalence of age-related disability and morbidity compared to the general population. An accelerated aging process has therefore been hypothesized as a component of the SCZ disease trajectory. Here, we investigated differential aging using three DNA methylation (DNAm) clocks (i.e. Hannum, Horvath, Levine) in a multi-cohort SCZ whole blood sample consisting of 1,100 SCZ cases and 1,200 controls. It is known that all three DNAm clocks are highly predictive of chronological age and capture different features of biological aging. We found that blood-based DNAm aging is significantly altered in SCZ with age- and sexspecific effects that differ between clocks and map to distinct chronological age windows. Most notably, the predicted phenotypic age (Levine clock) in female cases, starting at age 36 and beyond, is 3.21 years older compared to matching control subjects (95% CI: 1.92-4.50, P=1.3e-06) explaining 7.7% of the variance in disease status. Female cases with high SCZ polygenic risk scores present the highest age acceleration in this age group with +7.03 years (95% CI: 3.87-10.18, P=1.7E-05). Since increased phenotypic age is associated with increased risk of all-cause mortality, our findings suggests that specific and identifiable patient groups are at increased mortality risk as measured by the Levine clock. These results provide new biological insights into the aging landscape of SCZ with age- and sexspecific effects and warrant further investigations into the potential of DNAm clocks as clinical biomarkers that may help with disease management in schizophrenia.