Epigenetic modification of the oxytocin and glucocorticoid receptor genes is linked to attachment avoidance in young adults.

Attachment in the context of intimate pair bonds is most frequently studied in terms of the universal strategy to draw near, or away, from significant others at moments of personal distress. However, important interindividual differences in the quality of attachment exist, usually captured through secure versus insecure - anxious and/or avoidant - attachment orientations. Since Bowlby's pioneering writings on the theory of attachment, it has been assumed that attachment orientations are influenced by both genetic and social factors - what we would today describe and measure as gene by environment interaction mediated by epigenetic DNA modification - but research in humans on this topic remains extremely limited. We for the first time examined relations between intra-individual differences in attachment and epigenetic modification of the oxytocin receptor (OXTR) and glucocorticoid receptor (NR3C1) gene promoter in 109 young adult human participants. Our results revealed that attachment avoidance was significantly and specifically associated with increased OXTR and NR3C1 promoter methylation. These findings offer first tentative clues on the possible etiology of attachment avoidance in humans by showing epigenetic modification in genes related to both social stress regulation and HPA axis functioning.