Objective: to review the field of epigenetics, and present basic and recent material that may be of interest to clinical psychiatrists. We include basic molecular mechanism, a consideration of findings related to mental disorders, evidence of sustained effects, and the evidence for and implications of transgenerational epigenetic modifications. Method: we examined all the available papers for the last five years identified by PubMed using the words ‘epigenetics’ and ‘epigenetics psychiatry’, and the available leading specialized textbooks. Results: we report on molecular mechanisms including DNA and histone modifications, and non-coding RNAs. While some modifications are short-lived, others are life-long. Depression, suicide, schizophrenia, PTSD, borderline personality disorder and drug addiction are among the conditions for which epigenetic involvement has been proposed. Transgenerational epigenetics enables the environmental experience of one generation to be non-genetically inherited by subsequent generations. This has been molecularly demonstrated in laboratory animals and epidemically suggested in humans. Conclusions: epigenetics provides a new way of understanding human behavior and points to potential therapies for mental disorders. Should it transpire that transgenerational epigenetic modifications apply with force in humans as they do to laboratory animals, this will emphasize the need for cultural shift, safe societies with ample opportunities.