CLOCK and schizophrenia: Several lines of evidence have pointed towards the hypothesis of accelerated brain aging in schizophrenia.1, 2 In recent years, DNA methylation of 353 CpG sites (epigenetic clock) have been used to accurately estimate the biological age of human tissues and cell types.3 Studies have found epigenetic aging to be associated with Alzheimer’s disease,4 obesity5 and cancer.6 Only one study has investigated epigenetic aging in schizophrenia.7 Using postmortem brain samples from the superior temporal gyrus (n = 44), no acceleration of brain aging in schizophrenia was identified.