Abstract
Understanding the developmental timing of stress exposure may help inform mechanisms underlying how stress "gets under the skin" and influences the stress response system, including the HPA axis and its end-product cortisol. Early adversity may be particularly detrimental; however, it is difficult to disentangle the timing of adversity from its cumulative burden because there is typically high continuity between early and later adversity. Moreover, context and the different stressors inherent in various contexts may interact with stress exposure to influence psychophysiological functioning. To address this issue, we examined adolescents who had been reared in institutions and suffered neglect or social deprivation ranging from approximately six months to several years of life prior to adoption into U.S. homes. We focused on the stress hormone cortisol because it can reflect continued regulatory problems in youth, even years after youth transition to typical homes. We examined cortisol morning levels and diurnal rhythms across multiple contexts (home, school, lab) on 5 separate days in 41 post-institutionalized youth and 78 comparison youth. Employing hierarchical linear modeling, we found that when assessed in the lab, post-institutionalized (PI) youth displayed lower morning cortisol levels and flatter diurnal slopes than the control youth. Yet at home, PI youth displayed higher morning cortisol levels than the control youth. In addition to group effects, we also examined severity of early adversity and found that PI kids who had endured the most severe early adversity displayed lower home cortisol levels than controls. No significant predictors of diurnal cortisol on school days were identified. These data fit with the notion that the HPA axis is impacted by early adversity, even years after adoption, and with emerging theories that postulate that stress physiology calibrates within youth to help them adapt to their context. In the case of severe early adversity, the cost of such adaptation may not be desirable. It also highlights the important role of context when assessing HPA axis activity, particularly in post-institutionalized youth.