The biology of epigenetics has revolutionized every facet of medicine including psychiatry. Pridmore (2014) asserts that epigenetics has made more impact on psychiatry than on any other medical field. Genome-wide DNA methylation is the modern science used in the analysis of disease-associated methylation. DNA methylation is the key to several neurobiological and cognitive processes such as neurogenesis and brain development, neuronal activity, as well as learning and memory loss. Based on these observations, abnormal DNA methylation can be linked to psychiatric defects such as schizophrenia and bipolar disorder.
Genome-wide DNA methylation studies help in illuminating aberrant DNA methylation in psychiatric diseases. Various studies on epigenetic variation in psychiatric diseases have revealed methylated states of several genes. A study on rats to determine the features of mothering differences showed two traits that were passed to their offspring. Mothers with licking and grooming (LG) and arching back nursing (ABN) of pups produced mothers with the same qualities and vice versa. When the pups of low or high LG and ABN mothers were cross-fostered, the maternal qualities were inherited by the pups. The genome-wide DNA analysis revealed that there was a difference in DNA methylation of the glucocorticoid receptor (GR) gene promoter in the hippocampus (Roth, 2012). A similar study involving a suicide victim who had encountered abuse during childhood also showed discordance in glucocorticoid receptor (GR) gene promoter methylation. Genome-wide DNA analysis has been used to investigate the effects of depression, anxiety and SSRI medication from mother to child. Non, Binder, Kubzansky, and Michels (2014) show that there are significant changes in maternal CpG island when depression medication is used. Genome-wide DNA methylation analysis has enabled scientists to carry out global cross-association of psychiatric diseases. Melas et al. (2012) performed global DNA hypomethylation experiments to elucidate the global DNA hypomethylation in leukocytes of patients with schizophrenia. This study provided insight into the effects of commonly used SSRIs on DNA methylation.