Epigenetics and depression: return of the repressed.
BACKGROUND
Epigenetics has recently emerged as a potential mechanism by which adverse environmental stimuli can result in persistent changes in gene expression. Epigenetic mechanisms function alongside the DNA sequence to modulate gene expression and ultimately influence protein production. The current review provides an introduction and overview of epigenetics with a particular focus on preclinical and clinical studies relevant to major depressive disorder (MDD).


METHODS
PubMed and Web of Science databases were interrogated from January 1995 up to December 2012 using combinations of search terms, including "epigenetic", "microRNA" and "DNA methylation" cross referenced with "depression", "early life stress" and "antidepressant".


RESULTS
There is an association between adverse environmental stimuli, such as early life stress, and epigenetic modification of gene expression. Epigenetic changes have been reported in humans with MDD and may serve as biomarkers to improve diagnosis. Antidepressant treatments appear to reverse or initiate compensatory epigenetic alterations that may be relevant to their mechanism of action.


CONCLUSIONS
As a narrative review, the current report was interpretive and qualitative in nature.


CONCLUSIONS
Epigenetic modification of gene expression provides a mechanism for understanding the link between long-term effects of adverse life events and the changes in gene expression that are associated with depression. Although still a developing field, in the future, epigenetic modifications of gene expression may provide novel biomarkers to predict future susceptibility and/or onset of MDD, improve diagnosis, and aid in the development of epigenetics-based therapies for depression.
Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland; Department of Psychiatry, Trinity College Dublin, St. Patrick's University Hospital, James's Street, Dublin 8, Ireland.
Victoria S
VS
Dalton
Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland; Department of Psychiatry, Trinity College Dublin, St. Patrick's University Hospital, James's Street, Dublin 8, Ireland.
Erik
E
Kolshus
Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland; Department of Psychiatry, Trinity College Dublin, St. Patrick's University Hospital, James's Street, Dublin 8, Ireland. Electronic address: d.mcloughlin@tcd.ie.
Declan M
DM
McLoughlin
D003865:Major Depressive Disorder / Q000235:genetics*; D057890:Epigenomics; D015870:Gene Expression; D059647:Gene-Environment Interaction; D020022:Genetic Predisposition to Disease; D006801:Humans
DNA methylation; Depression; Epigenetics; Histone modification; microRNA