In humans, the primary product of this system is the steroid hormone cortisol ( Hennessy & Levine, 1979).
One of these systems is the hypothalamic-pituitary-adrenal (HPA) axis. Human and non-human animals have an interconnected set of complex physiological systems for managing physical, cognitive, and socio-emotional challenges. In particular, the theoretically important construct of attachment to both mothers and teachers as a potential buffering factor remains relatively understudied. It is less clear whether particular child characteristics and relationship characteristics might be important for predicting which children are protected from responding to the challenge of child care with HPA reactivity.
Although a focus on stress reactivity at child care is relatively new, efforts to understand this phenomenon have demonstrated that caregiving quality is important ( Dettling et al., 2000 Sims, Guilfoyle, & Parry, 2006 Tout et al., 1998 Watamura et al., 2009).
Specifically, increasing cortisol from morning to afternoon at full-day child care, in contrast with decreasing cortisol across the day for these same children at home, has been repeatedly demonstrated for toddlers and preschoolers ( Dettling, Gunnar, & Donzella, 1999 Dettling, Parker, Lane, Sebanc, & Gunnar, 2000 Watamura et al., 2003 Watamura, Kryzer, & Robertson, 2009). Previous work has shown that full-day, center-based child care is associated with increased reactivity of the hypothalamic-pituitary-adrenal (HPA) axis for many young children in the US (e.g., Tout, de Haan, Campbell, & Gunnar, 1998 Watamura, Donzella, Alwin, & Gunnar, 2003 Watamura, Sebanc, & Gunnar, 2002).