Does Stress Predict the Development of Internalizing Symptoms in Middle Childhood? : An Examination of Additive and Interactive Effects of Early, Daily, and Physiological Stress

Stress in individuals presents in various forms and may accumulate across development to predict maladaptive physical and psychological outcomes, including greater risk for the onset of internalizing symptoms. Early life stress, daily life experiences, and the stress response of the hypothalamic-pituitary-adrenal (HPA) axis have all been examined as potential predictors of the development of psychopathology, but rarely have researchers attempted to understand the covariation or interaction among these stress domains using a longitudinal design when looking at the influence of stress on internalizing psychopathology. Further, most research has examined these processes in adulthood or adolescence with much less attention given to the influence of these dynamic stress pathways in childhood. Guided by the biopsychosocial model of stress, this study explored early life stress, daily life stress, diurnal cortisol (cortisol AM slope), and internalizing symptoms in a racially/ethnically and socioeconomically diverse sample of twins participating in an ongoing longitudinal study (N=970 children; Arizona Twin Project; Lemery-Chalfant et al. 2013). An additive model of stress and a stress sensitization framework model were considered as potential pathways of stress to internalizing symptoms in middle childhood. Based on a thorough review of relevant literature, it was expected that each stress indicator would individually predict internalizing symptoms. It was also predicted that early life stress would moderate the associations between diurnal cortisol and internalizing symptoms, as well as daily life stress and internalizing symptoms. Multilevel modeling analyses showed that early life stress and cortisol AM slope, but not daily life stress, predicted internalizing symptoms. Early life stress did not moderate the associations between daily life stress and internalizing symptoms or cortisol AM slope and internalizing symptoms. Results support independent additive contributions of both physiological stress processes and early life parental stressors in the development of internalizing symptoms in middle childhood. Future investigation is needed to better understand the sensitizing effects of early parental life stress during this developmental stage.