Abstract
Allostatic load theory hypothesizes that stress and the body's responses to stressors contribute to longer term physiological changes in multiple systems over time (allostasis), and that shifts in how these systems function have implications for adjustment and health. We investigated these hypotheses with longitudinal data from two independent samples (n = 413; 219 girls, 194 boys) with repeated measures at ages 8, 9, 10, and 11. Initial parental marital conflict and its change over time indexed children's exposure to an important familial stressor, which was examined in interaction with children's respiratory sinus arrhythmia (RSA) reactivity to laboratory tasks (stress response) to predict children's basal levels of RSA over time. We also investigated children's sex as an additional possible moderator. Our second research question focused on examining whether initial levels and changes in resting RSA over time predicted children's externalizing behavior. Boys with a strong RSA suppression response to a frustrating laboratory task who experienced higher initial marital conflict or increasing marital conflict over time showed decreases in their resting RSA over time. In addition, boys' initial resting RSA (but not changes in resting RSA over time) was negatively related to change over time in externalizing symptoms. Findings for girls were more mixed. Results are discussed in the context of developmental psychobiology, allostatic load, and implications for the development of psychopathology.