Epigenetic Processes as Mediators of the Impact of the Social Environment

The enduring influence of early life social environments on lifelong wellbeing, health, and behavioral trajectories has garnered extensive attention in the fields of epidemiology and social sciences. Moreover, within the realm of psychiatric genetics, the concept of “gene-environment” interactions has shed light on how the early social environment may modulate the impact of genetic variants on later-life behavioral phenotypes. This interaction posits that while two individuals may both carry a risk allele for a particular behavioral phenotype, its manifestation may occur solely in a person who experienced childhood adversity. The existence of a statistical interaction between early environments and genetic variants suggests that environmental factors may operate through mechanisms that impact gene function. Epigenetics, a complex interplay of biochemical processes, orchestrates gene expression variations across different tissues, times, and spatial contexts without altering the underlying gene sequence. This phenomenon facilitates cellular differentiation in multicellular organisms, enabling one genome to yield diverse phenotypes in various tissues and organs during embryonal and postnatal development. Nearly two decades ago, it was hypothesized that epigenetic mechanisms which enable creating diverse phenotypes from one genome, might serve as the intermediaries linking early life social exposures to later-life physiological and behavioral outcomes. This chapter delves into a discussion of both animal data and human studies that substantiate this association, offering insights into the potential functional consequences of such links. The primary focus of this chapter centers on DNA methylation, a robust and extensively investigated epigenetic mechanism in this domain.