The University of Colorado - Anschutz Medical Campus in partnership with a tribal Early Head Start and behavioral health program will evaluate Parent-Child Interaction Therapy Intervention (PCIT) and the Emotional Availability Caregiver Intervention (EAI) to better understand the relationship between major environmental stressors and American Indian children's early development. Specifically, the project will: (1) examine the nature, extent and developmental course of environmental stressors among American Indian children between the ages of 10 and 48 months and explore hair cortisol as a marker of toxic stress; (2) implement PCIT with and without an EAI enhancement in a tribal behavioral health setting to serve American Indian children and families enrolled in Early Head Start; and (3) test the effectiveness of PCIT with and without EAI enhancement for decreasing the chronic stress response among children and their caregivers, increasing caregiver sensitivity, and decreasing behavior problems among children experiencing environmental stressors. The study will yield information about environmental stressors for American Indian children and their impact on development, and establish an evidence base for parenting interventions that may buffer children from the impact of stressors.