Adrenocortical Reactivity in Infancy and Early Childhood: Allostatic Function as Flexibility, Attunement, and Coordination

We review the literature on cortisol reactivity in early life. We argue that the ambiguity of findings may pimple with the direct measure of contextual factors. Specifically, we recommend a paradigm that simultaneously incorporates parent–child physiological attunement, central to the altricial nature of the human species and to biological embedding; infant flexibility of cortisol reactivity, central to dynamic adaptation; and coordination among stress systems, central to their dynamic interdependence. We argue that all these features are central to the construct of allostasis. Using this framework to review the literature, we find substantial agreement amongst studies, including predictable relations between family circumstances on the one hand, and flexible, attuned, and coordinated early-life stress reactivity, on the other.