Abstract
Animal and human research indicates that the early environment can exert effects on hypothalamic pituitary adrenal (HPA) axis functioning across the lifespan. Using data from the National Study of Midlife Development in the United States and the National Study of Daily Experience substudy, we identified curvilinear relations between adult reports of parental affection in childhood and adult diurnal cortisol rhythms. Reports of both very affectionate and very unaffectionate parental relations in childhood were associated with flatter diurnal rhythms, suggesting potential dysregulation of the HPA axis at both extremes of family environment. Participants in the bottom tertile showed more signs of HPA axis dysregulation than those in the top tertile. We discuss processes that may underlie these effects, with reference to the theory of allostatic load.