Causal effects of the early caregiving environment on development of stress response systems in children

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 18; pp. 5637 - 5642
• Main Authors: McLaughlin, Katie A., Sheridan, Margaret A., Tibu, Florin, Fox, Nathan A., Zeanah, Charles H., Nelson, Charles A.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 05.05.2015; National Acad Sciences
• Subjects: animal models; autonomic nervous system; Autonomic Nervous System - physiopathology; Caregivers; Causality; Child care; Child, Institutionalized - psychology; Child, Preschool; children; Children & youth; Electrocardiography; Foster Home Care - psychology; human development; Humans; Hydrocortisone - metabolism; Hypersensitivity; Hypothalamo-Hypophyseal System - physiology; Infant; Longitudinal Studies; Nervous system; Pituitary-Adrenal System - physiology; Rodents; Romania; Social Sciences; Stress response; Stress, Psychological - physiopathology; Stress, Psychological - psychology; Time Factors; Romania; Romania, Bucharest; stress reactivity; HPA axis; autonomic nervous system; early-life stress; childhood adversity
• DOI: 10.1073/pnas.1423363112
• ISSN: 0027-8424; 1091-6490

Significance Disruptions in stress response system functioning are thought to be a central mechanism by which exposure to adverse early-life environments influences human development. Although rodent models support this possibility, results from human studies have been decidedly mixed. Using data from an experimental study examining whether random assignment to a caregiving environment alters development of the autonomic nervous system and hypothalamic–pituitary–adrenal axis in humans, we provide causal evidence for persistent effects of the early caregiving environment on stress response system functioning in humans with effects that differ markedly from those observed in rodent models. We also provide evidence of a sensitive period in human development during which the environment is particularly likely to alter stress response system development. Disruptions in stress response system functioning are thought to be a central mechanism by which exposure to adverse early-life environments influences human development. Although early-life adversity results in hyperreactivity of the sympathetic nervous system (SNS) and hypothalamic–pituitary–adrenal (HPA) axis in rodents, evidence from human studies is inconsistent. We present results from the Bucharest Early Intervention Project examining whether randomized placement into a family caregiving environment alters development of the autonomic nervous system and HPA axis in children exposed to early-life deprivation associated with institutional rearing. Electrocardiogram, impedance cardiograph, and neuroendocrine data were collected during laboratory-based challenge tasks from children (mean age = 12.9 y) raised in deprived institutional settings in Romania randomized to a high-quality foster care intervention ( n = 48) or to remain in care as usual ( n = 43) and a sample of typically developing Romanian children ( n = 47). Children who remained in institutional care exhibited significantly blunted SNS and HPA axis responses to psychosocial stress compared with children randomized to foster care, whose stress responses approximated those of typically developing children. Intervention effects were evident for cortisol and parasympathetic nervous system reactivity only among children placed in foster care before age 24 and 18 months, respectively, providing experimental evidence of a sensitive period in humans during which the environment is particularly likely to alter stress response system development. We provide evidence for a causal link between the early caregiving environment and stress response system reactivity in humans with effects that differ markedly from those observed in rodent models.