Author: Platje E, et al. (2013) Psychoneuroendocrinology.
In the current study, the researchers examined the mediating role of deviant peers in the level of hypothalamic-pituitary-adrenal (HPA) axis activity to aggression and rule-breaking. As a measure of HPA axis activity, cortisol was assessed at awakening, 30, and 60min later (the cortisol awakening response, CAR). Participants, as well as their best friend, reported on their own aggressive and rule-breaking behavior. Aggression was only predicted by a decreased cortisol level at awakening, and not by aggressive behavior of their friend. Decreased levels of cortisol at awakening predicted adolescents' rule-breaking, which subsequently predicted increased rule-breaking of their best friend. These findings suggest that interrelations between biological and social risk factors are different for the development of aggression versus rule-breaking. Furthermore, decreased levels of HPA axis activity may represent a susceptibility to selecting deviant peers.