Depression and schizophrenia. There are many interesting studies indicating persisting epi-
genetic marks can be acquired depending on early life environment and life experiences that can
lead to subsequent altered adult behavior. For example, mother rats that exhibit strong nurtur-
ing behaviors toward their pups, manifest by frequently licking and grooming their offspring,
produce lasting alterations in the patterns of DNA methylation in the CNS of their pups (36).
These changes in methylation can persist throughout adulthood. In this vein, studies by Meaney
and colleagues (37, 73) have presented evidence that these changes in DNA structure result in
decreased anxiety and a strong maternal nurturing instinct in the adult offspring. These studies
have recently been extended into studies of human experiential effects on DNA methylation and
their potential role(s) in depression and suicide (111–113).