All specimens were flash-frozen, and screened for macro- and microscopic neuropathological abnormalities, as previously described44. All specimens with significant evidence of neurological disorders, infarcts or other cerebrovascular abnormalities were excluded from study. Brain pH was measured, and postmortem interval (PMI, in hours) was calculated for every sample. Postmortem tissue homogenates of the prefrontal cortex (dorsolateral prefrontal cortex, DLPFC, BA46/9) were obtained from all subjects. Genomic DNA was extracted from 100 mg of pulverized dorsolateral prefrontal cortex (DLPFC) tissue with the phenol-chloroform method. Bisulfite conversion of 600 ng genomic DNA was performed with the EZ DNA methylation kit (Zymo Research).
