RecruitingEarly Phase 1Drug trialNaltrexone Neuroimaging in Teens With Eating DisordersUsing a randomized, placebo-controlled, crossover study, this study will evaluate functional magnetic resonance imaging (fMRI) as a pharmacodynamic biomarker of opioid antagonism in adolescents with eating disorders. The hypothesis is that fMRI will be able to detect acute reward pathway modulation by naltrexone (an opioid antagonist) in pre-defined regions of interest (anterior cingulate cortex, nucleus accumbens, dorsolateral prefrontal cortex).