Hypothalamic pituitary adrenal activity and autonomic nervous system arousal predict developmental trajectories of children's comorbid behavior problems.

The combined effects of hypothalamic-pituitary-adrenal (HPA) axis activity and autonomic nervous system (ANS) arousal were examined on developmental trajectories of children's comorbid internalizing and externalizing problems. Participants were 394 urban dwelling, primarily African American, youth (50% male, age 11-12 years). Parent-reported child behavior problems were obtained initially, 3, 6, and 12 months later. Saliva samples (collected at the initial assessment) were assayed for cortisol (HPA) and alpha-amylase (ANS). Cross-domain latent class growth analysis identified a stable comorbid trajectory and four other distinct short-term developmental trajectories of internalizing and externalizing behavior problems. ANS arousal was negatively associated with the probability of stable comorbidity, but only among youth who also had high levels of HPA axis activity. Findings underscore the predictive value of the interaction of HPA axis activity and ANS arousal in differentiating children with stable comorbidity and have important implications for etiological theories and treatment outcome research.