Early adversity, child neglect, and stress neurobiology: From observations of impact to empirical evaluations of mechanisms

Research on the effects of early life adversity, and in particular on the absence of responsive caregiving, has shown long-term impacts on well-being and development. These investigations have been conducted both in human populations and in animal models. The work has demonstrated that neglect experienced in the early years can affect not only behavior but also neurobiological functioning. In particular, studies of children in the foster care system show convergence with research on children adopted following institutional rearing in terms of dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, which produces the neuroendocrine hormone cortisol. The characteristic pattern that has been most commonly observed involves diminished diurnal cortisol production, particularly in terms of low levels of cortisol upon awakening. Notably, however, a number of evidence-based interventions for infant, toddler, and preschool-aged foster children have been shown to produce more typical patterns of cortisol production, in combination with improved behavioral, socioemotional, and foster care placement outcomes. In this paper, we review the literature on the effects of early disruptions in care on biobehavioral development, and summarize the results of the interventions for young foster children.