Modified Project Summary/Abstract Section External stressors have implications for the health and well-being of families and children, including increased domestic violence and harsh parenting. Despite evidence indicating that these may increase rates of interparental hostility and parent-child difficulties, little is known about the lasting effect on families, particularly how it may modulate the degree and nature of the interdependencies between family relationships or subsystems in ways that modify family functioning. Grounded in the theoretically rich conceptualizations of family systems and spillover processes, this application seeks to explore how the extra-familial perturbations modify associations between interparental hostility and discord and harsh, punitive parenting. This application builds on an existing dataset (Phase 1, N = 235 families) that was collected over a three-year period immediately and we propose to collect three additional waves of data to continue to chart longitudinal effects. The strength of this application involves the utilization of a quasi-experiment design for family functioning, and both phases (six waves in total) will utilize multi-method, multi-informant, and multi-level longitudinal design to assess ecological contexts, family dynamics, parent and child characteristics, and parenting behaviors. This study will elucidate how external stressors may influence spillover processes and may have enduring effects on family functioning and advance new process-oriented approaches through the mediating mechanism of parental neurobiological and cognitive self-regulation. Furthermore, the present application will identify the preexisting factors as risk or protective factors in the spillover processes. The results of this application will have significant implications for understanding family functioning and have high potential to generate knowledge on targets for evidence-based prevention programs.