HPA stability for children in foster care: Mental health implications and moderation by early intervention

Research on stress-sensitive biological systems has typically focused on activation at one time, yet recent theories emphasize dynamic, context-specific adaptation. This study tested hypothesized calibration of one such system by examining both mean levels and longitudinal stability of daily cortisol—reflecting hypothalamic-pituitary-adrenal axis activation—in children exposed to high-risk versus lower-risk caregiving contexts. Context-specific effects of longitudinal cortisol profiles were addressed via relations with child psychiatric symptoms. Children from regular foster care, foster children participating in a family-based intervention, and community comparison children (n=96 total) collected saliva samples for cortisol assay at 29 timepoints across 6+ years. High-risk (regular foster care) children showed lower and more variable cortisol levels than their lower-risk (treatment foster care, community comparison) counterparts. For the high-risk children only, higher and more stable cortisol related to elevated anxiety symptoms. Implications for contextual calibration of stress systems and family intervention mechanisms are discussed.