Epigenetics, Early Adversity and Child and Adolescent Mental Health.

Epigenetic modification, such as DNA methylation (DNAm), is a mechanism that can help explain how early adversities can engender long-term vulnerability for mental health problems. At present, there is preliminary evidence to support the possibility of epigenetic mediation: environmental factors are reported to influence offspring DNAm, which in turn associate with child and adolescent psychopathology. However, all analyses have been correlational in nature and, as these studies have focussed on children and adolescents, DNAm has been based on peripheral tissue (cord blood, whole blood, buccal cells). Therefore, the extent to which DNAm could represent a causal mechanism (e.g., a surrogate of central nervous system function) or a biomarker (i.e., an indicator of the pathological process leading to disease) is unclear. This short report has 2 main components. First, 2 studies are summarized, one a candidate gene study and the other an epigenome-wide association study in which DNAm was reported to (partially) mediate the link between adversity and child development. Second, there is a discussion of (1) the "tissue issue," (2) maximizing the interpretability of candidate gene and epigenome-wide approaches, and (3) the need for examining DNAm as a potential biomarker for mental health. It is argued that advances within these 3 areas will make clearer the role of DNAm in the link between adversity and child and adolescent mental health.