Children’s Cortisol in Preschool and Aggression One Year Later in Kindergarten

Abstract

Previous research has examined associations between aggression and cortisol throughout the lifespan, with most studies concluding that individuals with lower basal cortisol exhibit more aggressive and antisocial behavior. However, studies investigating links between aggression and cortisol in young children are unclear. The purpose of this study was to examine basal and reactive cortisol in preschool and whether it was predictive of concurrent and later aggression. Preschool children (N = 189) enrolled in community child care programs served as participants. Cortisol was measured in saliva samples collected from children at child care. Samples collected on two mornings were used as an index of basal cortisol. Samples collected over the course of a series of challenging tasks and teacher-child interaction served as indices of reactive cortisol. Teachers provided ratings of child aggression in preschool and in kindergarten. Multiple models were fit using path analysis examining associations among cortisol measures, aggression during preschool, and aggression a year later in kindergarten. In a model examining basal (i.e., morning) cortisol, controlling for preschool aggression and time of saliva collection, lower morning cortisol predicted higher aggression in kindergarten a year later. In a model examining reactive cortisol, declines in cortisol over the challenging tasks was associated with higher aggression ratings concurrently, whereas increasing cortisol during teacher-child interaction predicted higher aggression ratings a year later in kindergarten. When both basal and reactive cortisol were included in the same model, only basal cortisol predicted kindergarten aggression.