New hope: the emerging role of 5-hydroxymethylcytosine in mental health and disease.

Historically biomedical research has examined genetic influences on mental health but these approaches have been limited, likely due to the broad heritability of brain-related disorders (e.g., 30-90%). Epigenetic modifications, such as DNA methylation, are environmentally sensitive mechanisms that may play a role in the origins and progression of mental illness. Recently, genome-wide disruptions of 5-hydroxymethylcytosine (5hmC) were associated with the development of early and late onset mental illnesses such as autism and Alzheimer's disease, bringing new hope to the field of psychiatry. Here, we review the recent links of 5hmC to mental illness and discuss several putative functions of 5hmC in the context of its promising clinical relevance.