Animal studies reveal that early deprivation impairs regulation of the hypothalamic-pituitaryadrenocortical (HPA) axis, potentially increasing vulnerability to stressors throughout life. To examine early deprivation effects on basal HPA axis activity in humans, basal cortisol levels were examined in 164 internationally adopted children who had experienced varying degrees of preadoption deprivation. Duration of institutional care, age at adoption, and parent ratings of preadoption neglect indexed a latent factor of Deprived Care. Adoption measures of height and weight standardized to World Health Organisation norms indexed a latent factor of Growth Delay that was viewed as another reflection of deprivation. Cortisol samples were collected 3.3-11.6 years postadoption (Md = 7.3 years) at home on 3 days approximately 30 min after wakeup and before bedtime. Both early a.m. levels and the decrease in cortisol across the day were examined. A structural equation model revealed that preadoption Deprived Care predicted Growth Delay at adoption and Growth Delay predicted higher morning cortisol levels and a larger diurnal cortisol decrease.Children who are neglected and abused early in life are at heightened risk for physical and mental disorders (Cicchetti & Toth, 1995). There is currently considerable interest in understanding how adverse early care influences brain development and contributes to individual differences in vulnerability (e.g., Cicchetti & Tucker, 1994). Animal studies of the impact of early adverse experiences on the hypothalamic-pituitary-adrenocortical (HPA) system provide a compelling explanatory model (e.g., see Graham, Heim, Goodman, Miller, & Nemeroff, 1999;Heim, Owen, Plotsky, & Nemeroff, 1997). However, their applicability to human development remains uncertain. Glucocorticoids (cortisol in primates, corticosterone in rodents) are hormones produced by the HPA axis that are essential both for maintaining homeostasis and adapting to physical and psychological stressors (de Kloet, Rots, & Cools, 1996;Sapolsky, Romero, & Munck, 2000). Although increases in glucocorticoids above basal levels are typically examined in research on stress, basal levels also contribute importantly to stress vulnerability and resilience (Sapolsky et al., 2000). According to the allostatic load model (McEwen, 1998), the HPA system supports adaptation to stress through increasing or decreasing its basal set points and responsiveness. These changes, although permitting individuals to continue to function, carry a risk or allostatic load that increases vulnerability to physical and mental disorders. Indeed, both Address correspondence and reprint requests to: Megan R. Gunnar, Institute of Child Development, 51 East River Road, University of Minnesota, Minneapolis, MN 55455; gunnar@umn.edu. HHS Public AccessAuthor manuscript Dev Psychopathol. Author manuscript; available in PMC 2018 March 22. Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript chronically elevated and chronically suppressed basal gluco...