Longitudinal DNA methylation and cell-type proportions alterations in risperidone treatment response in first-episode psychosis.

Identifying biological markers to guide treatment decisions in first-episode psychosis (FEP) is essential for improving patient outcomes. This longitudinal study investigated DNA methylation (DNAm) patterns and DNAm-derived cell-type proportions (CTP) in blood and associated them with response to risperidone treatment, a second-generation antipsychotic drug, in antipsychotic-naïve FEP patients. We also explored longitudinal changes in DNAm associated with risperidone treatment. We profiled DNAm in 114 individuals before (anFEP) and after two months of risperidone treatment using microarrays. The main results were compared with 115 healthy controls and validated in an independent cohort of subjects with schizophrenia (n = 26) with one-month follow-up data. We identified 302 differentially methylated positions (DMPs) associated with treatment response, measured by changes in the Positive and Negative Syndrome Scale score, of which 16 were validated in the independent cohort. Sixteen differentially methylated regions (DMRs) were associated with response, with one (in SIPA1L3) being validated. A decrease in B-cell proportions was correlated with symptom improvement in both cohorts. Additionally, four DMPs associated with risperidone treatment were identified: two related to the psychotic state and two specifically to risperidone treatment. DNAm-derived CTP showed alterations in anFEP compared with controls, particularly in the neutrophil-to-lymphocyte ratio, which normalized after treatment. These findings suggest that DNAm, particularly in B-cells, may be a promising marker for monitoring response to risperidone treatment in schizophrenia. Our longitudinal study revealed novel and known genes that may be regulated by risperidone and could be used as response markers to improve prognosis in schizophrenia and FEP.