Social deprivation and the HPA axis in early development.

Growing evidence suggests that early social deprivation impacts the activity of the hypothalamic-pituitary-adrenocortical axis. Early adverse care in the form of institutional or orphanage care provides a human model for early social deprivation. The present study examined changes in diurnal cortisol during the transition to family care in the first 2 years post-adoption. Children adopted between 15 and 36 months from institutional care were examined four times during their first 2 years post-adoption (N=58). Comparison groups included same-aged peers reared in their birth families (N=50) and children adopted during their first year from overseas foster care (N=47). Children provided daily cortisol samples at roughly 2, 9, 17, and 25 months post-adoption. Post-institutionalized and post-foster care children exhibited less steep diurnal cortisol compared to non-adopted same-aged peers; these differences did not diminish across the 2 year period. For post-institutionalized children, lower social care quality in institutions was associated with less steep cortisol slopes. Lastly, shallower diurnal cortisol was a mediator between adoption status and increased behavioral problems 2 years post-adoption. Consistent with the non-human primate literature, early social deprivation may contribute to early programming of the HPA axis.