Abstract:

The purpose of the present study was to investigate how family influences, including parenting quality, sibling relationship quality, and the family environment, and children's temperament, specifically negative affectivity, relate to children's stress response physiology. The current study tested two competing theories, Evolutionary Developmental Theory (EDT) and the linear theory. Multiple family influence and temperament measures were used, both questionnaire and observational in nature, to assess predictors of children's salivary cortisol levels in a sample of 459 pairs of twins originating from the Wisconsin Twin Project. A multi-level growth curve analysis accounted for twin interdependence and modeled change in cortisol levels over time. Findings indicated that none of the family influence or temperament variables significantly predicted either a growth curve intercept or slope in cortisol. Therefore, this study failed to find support for either EDT or the linear theory. However, this nonassociation may be adaptive from an evolutionary perspective such that stress hormone systems are not related to broad family influences but to more context specific events. Additionally, children who reside in extremely risky environments maybe most influenced regarding cortisol levels where children living within a more typical or normal range of environments are less affected.