Eating disorders are common in adolescents, increase the risk of substance use, have the highest mortality rate of any psychiatric illness and are not responsive to current pharmacotherapy. The overall goal of this K23 proposal is to evaluate neuroimaging as a pharmacodynamic biomarker of opioid antagonism in adolescents with eating disorders through practical application of training in neuroimaging, pediatric randomized clinical trials and exposure-response modeling. At the completion of this proposal, Dr. Stephani Stancil will be well- positioned for an independent career as an interdisciplinary translational scientist focused on pharmacodynamic biomarker development to support early-stage drug development in pediatric neuropsychopharmacology.