Early life stress (ELS) is expected to increase reactivity of the hypothalamic-pituitary-adrenocortical (HPA) axis; however, several recent studies have shown diminished cortisol reactivity among adults and children with ELS exposure. The goal of this study was to examine cortisol activity in 10-12-year-old internationally adopted children to determine if moderate and severe ELS have different impacts on the HPA axis. Salivary cortisol and two measures of autonomic activity were collected in response to the Trier Social Stress Test for Children (TSST-C). Three groups reflecting moderate, severe, and little ELS were studied: early adopted children who came predominantly from foster care overseas (early adopted/foster care (EA/FC), n = 44), later adopted children cared for predominantly in orphanages overseas (late adopted/post-institutionalized (LA/PI), n = 42) and non-adopted (NA) children reared continuously by their middle- to upper-income parents in the United States (n = 38). Diminished cortisol activity was noted for the EA/FC group (moderate ELS), while the LA/PI group (severe ELS) did not differ from the NA group. Overall, few children showed cortisol elevations to the TSST-C in any group. The presence/absence of severe growth delay at adoption proved to be a critical predictive factor in cortisol activity. Regardless of growth delay, however, LA/PI children exhibited higher sympathetic tone than did NA children. These results suggest that moderate ELS is associated with diminished cortisol activity; however, marked individual differences in cortisol activity among the LA/PI children suggest that child factors modify the impact of severe ELS. Lack of effects of severe ELS even for growth delayed children may reflect the restorative effects of adoption or the generally low responsiveness of this age group to the TSST-C.
- Early life stress
- Group-based trajectory modeling
- Growth curve modeling
- Internationally adopted children
- Linear mixed modeling