PROJECT SUMMARY/ABSTRACT Anorexia nervosa (AN) is a serious psychiatric illness that affects ~1% of adolescents and is associated with high rates of morbidity and mortality. Family-based treatment (FBT), which involves empowering caregivers to take control of refeeding to restore the adolescent to a normative weight and eating trajectory, is postulated to operate via increasing caregiver self-efficacy related to refeeding, and decreasing adolescent distress through repeated exposure to eating- and weight-related stimuli. Although FBT is currently considered the “first line” treatment for adolescent AN, it is underutilized in community settings and is unavailable to many families for a multitude of practical reasons (e.g., costs of treatment, limited availability of trained providers in many regions of the country), particularly those from underrepresented sociodemographic groups. Furthermore, a substantial subset of families do not optimally respond to FBT, which may be due to failure of newly acquired intervention skills to generalize outside of the (typically office-based) treatment context. Home-based treatment is an alternative to traditional office-based outpatient treatment that can reduce many pragmatic barriers to treatment uptake and engagement, and may enhance generalizability of treatment skills as it is delivered in multiple naturalistic settings where refeeding often occurs (e.g., home, school, community). Although home-based models have been successfully applied to other psychiatric conditions, home-based treatments for AN have never been tested. Moreover, FBT has undergone limited investigation in “real world” settings outside of specialty academic and clinical environments dedicated to eating disorders. As a result, much of what is known about FBT is based on relatively homogeneous samples with limited representation from individuals from lower income and racial/ethnic minority backgrounds. Furthermore, it is unclear if putative FBT mechanisms apply in the effectiveness context. The proposed R34 pilot effectiveness trial will assess outcomes, implementation, and mechanisms of FBT for adolescent AN adapted for the home setting (FBT-HB), delivered in the context of two community-based behavioral health agencies that serve a primarily lower-income, racially and ethnically diverse clientele. Adolescents with AN-spectrum disorders (n=50) and their caregivers will be randomly assigned to either FBT-HB or home-based usual care (integrated family therapy approach). Caregivers and adolescents will provide data on weight, eating, and putative treatment mechanisms, including caregiver self- efficacy, adolescent distress, and generalizability of treatment skills. Implementation constructs will be measured among providers and participating families. Overall aims are to assess preliminary effects of FBT- HB on adolescent eating and weight outcomes; FBT-HB acceptability, appropriateness, feasibility, and fidelity; and caregiver- and adolescent-l...