Studies examining peripheral DNA methylation have also identified epigenetic signatures of childhood maltreatment. In candidate gene studies examining methylation of the gene that encodes the serotonin transporter (i.e. SLC6A4), individuals that experienced abuse during childhood demonstrate increased methylation of the SLC6A4 promoter and reduced SLC6A4 expression (Beach et al., 2010; Vijayendran et al., 2012). The serotonin transporter is important for emotional regulation (Hariri and Holmes, 2006), and reduced SLC6A4 expression has been linked with suicidal behavior, particularly in individuals that experienced childhood maltreatment (Roy et al., 2007). Genome-wide investigation revealed that children experiencing severe maltreatment had differential methylation at 2,868 CpG sites (Yang et al., 2013). Some of the genes exhibiting differential methylation were involved in neural communication, immune response, and brain development. These data show the ability for childhood abuse to alter methylation at multiple gene loci in the brain and periphery.
