The hypothalamic-pituitary-adrenocortical (HPA) axis may be impaired in infants who were institutionalized during infancy; however, the peripubertal period may be an important time in child development in which improving environment supportiveness may have a substantial impact on HPA axis and stress-mediating systems, according to study results published in the Proceedings of the National Academy of Sciences.
Previous studies have shown that the unsupportive environment of an orphanage can calibrate the defensive system and the original calibration is maintained even years after adoption into supportive homes. This has led to the theory that simply removing children from deprivation and placing them in supportive, well-resourced homes does not suffice to allow recalibration of the HPA axis.
The goal of the study was to assess whether pubertal development opens a window of opportunity for changes in the HPA axis in post-institutionalized children who tend not to be seen prior to puberty when children shift from harsh deprived conditions in infancy into supportive, well-resourced homes in childhood and adolescence.
The study cohort included 129 post-institutionalized children (mean age, 11.38 years; 68.22% girls) and 170 non-adopted children (mean age, 11.20 years; 52.35% girls) who completed 3 annual sessions beginning at ages 7 to 15. At each session, trained nurses conducted pubertal staging and collected saliva samples across a 2-hour period, capturing cortisol reactivity and recovery in response to a modified version of the Trier Social Stress Test for Children (TSST-C).
Salivary cortisol reactivity and pubertal status were characterized in 299 children and adolescents.
The data provide within-individual evidence of pubertal recalibration of the HPA axis in humans. In post-institutionalized youth, within-individual increases in pubertal stage significantly predicted increased (eg, more typical) cortisol stress reactivity, as least square mean contrasts indicated that cortisol reactivity at pubertal stages 1 and 5 were significantly different in this group. However, in the non-adopted youth group there were no significant differences in cortisol reactivity at any pubertal stage.
“This suggests that intervention efforts to improve outcomes for children who have experienced early life adversity should include a focus on the prepubertal and peripubertal period in order to maximize their impact on recalibrating systems like the HPA axis,” concluded the researchers.
Gunnar MR, DePasquale CE, Reid BM, Donzella B. Pubertal stress recalibration reverses the effects of early life stress in postinstitutionalized children. [published online November 11, 2019]. Proc Natl Acad Sci USA. doi:10.1073/pnas.1909699116