The neurobiology of violence and trauma: Understanding the consequences of early life adversity through the study of sex differences in environment and perception

The neurobiology of violence and trauma was studied to provide support for a contextsex differences model of maltreated and nonmaltreated youth. Specifically, the three reports presented in this dissertation examine the short- and long-term effects of exposure to violent and traumatic experiences and perception of abuse on hypothalamic-pituitary-adrenal (HPA) axis function and internalizing and externalizing behavior problems during childhood and adolescence. Sex differences were considered as males and females are thought to differ in their biobehavioral response to stress (Taylor et al., 2000) and in the manifestation of health and behavior problems related to severe and chronic stress exposure (Klein & Corwin, 2002). The first study is a critical review of the stress literature pertaining to HPA axis function in children and adolescents, with the purpose of highlighting differences in HPA axis function between males and females in the context (e.g., community violence, maltreatment) in which children and adolescents develop. The second report assessed adaptation and calibration of the stress response system by examining the association between recent exposure to violent and traumatic experiences and cortisol reactivity over time in maltreated and nonmaltreated youth. The third report tested hypotheses regarding whether maltreated children's perception of abuse as their most upsetting experience was associated with the development of internalizing and externalizing behavior problems and HPA axis function in males and females, separately. The aims of these studies are to consider exogenous (e.g., environmental) and endogenous (e.g., sex, perception) factors that may explain inconsistencies in the stress literature and why some children and adolescents are resilient in the face of adversity. Data for the second and third reports were provided by the Young Adolescent Project (YAP), a longitudinal study that followed an ethnically diverse sample of maltreated (n = 303) and nonmaltreated (n = 151) children and adolescents over four waves of measurement. The studies that provided data for Reports 1 and 2 were funded by the National Institute of Child Health (NICHD) and the National Institute of Drug Abuse (Penelope K. Trickett, PI). Results for the three reports provide support for a context-sex differences model, showing that exogenous factors such as the presence of violence and endogenous factors such as sex, lead to differences in biobehavioral responses to stress. Furthermore, the findings suggest that the presence and perception of early life stressors, such as maltreatment, may set children on a trajectory for dysregulated HPA axis activity and the manifestation of health and behavior problems.