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

Abstract

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 laboratorybased challenge tasks from children (mean age = 12.9 y) raised in deprived institutional settings in Romania randomized to a highquality 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.childhood adversity | early-life stress | HPA axis | autonomic nervous system | stress reactivity D isruptions in stress response system functioning are thought to be a central mechanism by which exposure to adverse early-life environments influences human development. This idea is borne out in rodent models, where the effects of early-life adversity on the development of stress response systems have been well characterized. Exposure to early-life adversityinvolving repeated and prolonged separation of a pup from its mother-results in hyperreactivity of the sympathetic nervous system (SNS) and the hypothalamic-pituitary-adrenal (HPA) axis in adolescence and adulthood and elevations in anxiety, fearful behaviors, and hypervigilance (1-4). Stress exposure in mature rodents is associated with immediate, but not lasting, changes in stress response systems (5, 6), suggesting the presence of an early sensitive period when exposure to adverse environments results in long-term changes in physiological stress response system functioning.

HPA axis dysregulation in adult adoptees twenty years after severe institutional deprivation in childhood

“…Group differences in the CAR with a complete lack of a response in the most severely deprived and an attenuated pattern in the group with short duration of deprivation are consistent with the fairly uniform observation of a pattern of hypocortisolism in institutionalized and postinstitutionalized children at much younger ages. Our findings are also consistent with a previous finding that late removal from institutions (between 18 and 24 months) is associated with hyporeactivity in response to stress, while the same is less apparent with earlier removal (Koss et al, 2016;McLaughlin et al, 2015).…”

“…It cannot be ruled out that disturbed cortisol regulation is a late appearing consequence of institutional deprivation. However, given findings by other groups who have prospectively assessed HPA axis function in institutionalized and post-institutionalized children (Koss et al, 2016;McLaughlin et al, 2015), and given our own findings of early appearing deprivationspecific problems which are highly persistent and are not eradicated by the overall very positive post-adoption experience, it is likely that HPA axis dysregulation also constitutes an early appearing and stable phenotype associated with institutional rearing. In light of the evidence of decreased cortisol activity and reactivity in adults and children with experience of early adversity (Carpenter et al, 2007;Elzinga et al, 2008;Lovallo et al, 2011;Miller et al, 2007;Power et al, 2012;Schwaiger et al, 2016), it has been proposed that sustained periods of chronic stress, such as psychosocial deprivation and neglect, are initially associated with high levels of circulating cortisol, followed by counter-regulation which eventually results in decreased HPA axis re-/ activity.…”

“…Koss et al found blunted HPA axis reactivity in deprived and adopted one to three year old infants relative to non-adopted controls during the transition to adoptive family care − effects that persisted for a number of years post adoption (Koss et al, 2014;Koss et al, 2016). The Bucharest Early Intervention Project reported a blunted cortisol response in children who remained in institutional care compared with children randomized to foster care before (rather than after) age two yearsproviding evidence of a relationship between deprivation dose and HPA effects (McLaughlin et al, 2015). One long-term follow-up into adulthood found lower morning cortisol levels and flatter diurnal slopes in adoptees who experienced severe neglect or abuse compared to nonabused individuals (van der Vegt et al, 2009).…”

EEG Correlation during Social Decision-making in Institutionalized Adolescents

“…Also, it has been found a generalized lower alpha power which is positively related to social skills according to a maturational patter found on institutionalized children placed on a foster care home before 20 months of age [16]. Finally, it has been demonstrated that the more time for children living in institutional settings, the more affectation this population suffers [17].…”

“…Also, it has been found a generalized lower alpha power which is positively related to social skills according to a maturational patter found on institutionalized children placed on a foster care home before 20 months of age [16]. Finally, it has been demonstrated that the more time for children living in institutional settings, the more affectation this population suffers [17].In relation with behavioral and cognitive consequences, diverse studies have found that the institutionalized children present impulsivity [18], social problems and delinquent behavior [19], as well as, affectation in cognitive functions like working memory, inhibitory control, memory for faces and visual attention [2,5]. Talking about social abilities, it has been demonstrated that children that was previously institutionalized and were randomly assigned to a foster care intervention program have better social abilities with less social communication problems compared to institutionalized children [20].…”