What do DNA methylation studies tell us about depression? A systematic review

Area of Science:

• Epigenetics
• Neuroscience
• Psychiatry

Background:

• Limited systematic reviews exist on DNA methylation and depression.
• Understanding the influence of study characteristics on findings is crucial.

Purpose of the Study:

• To critically appraise the impact of study characteristics on the DNA methylation-depression association.
• To summarize the current overview of DNA methylation in depression.

Main Methods:

• Systematic review of English-language studies (until December 2017) using standard depression diagnostic criteria.
• Included 67 studies, categorizing findings into etiological and treatment categories.
• Analyzed study characteristics, common tissues (whole blood), and DNA methylation testing methods (bisulfite conversion, pyrosequencing).

Main Results:

• DNA methylation modifications are generally associated with depression.
• Most studies found BDNF and SLC6A4 hypermethylation linked to major depressive disorder (MDD).
• Inconsistent findings were reported for NR3C1, OXTR, and other genes due to limited studies.

Conclusions:

• DNA methylation plays a role in depression.
• High heterogeneity in methodologies necessitates caution in interpretation.
• Future longitudinal studies with standardized methods are needed for quantitative synthesis.