PROJECT SUMMARY/ABSTRACT Eating disorders (EDs) are serious mental illness, with the second highest mortality rate of any psychiatric disorder and carry high societal, personal, and economic costs. Treatment response for EDs are suboptimal, with only 50% of adults responding to evidence based treatments and no evidence-based treatment for anorexia nervosa (AN) or Other Specified Feeding or Eating Disorder (OSFED) in existence. Part of the reason EDs are so difficult to treat is the high heterogeneity in symptom presentation, making it difficult to identify what to target in treatment, as two individuals, even with the same diagnosis, substantially vary. Personalized treatments for EDs are urgently needed that can improve treatment response and minimize the suffering associated with these illnesses. Our scientific premise, developed from our past work, is that treatment personalized based on idiographic models (termed Network Informed Personalized Treatment; NA-PT) will outperform the current gold-standard treatment (Enhanced Cognitive Behavioral Therapy: CBT-E). Our study goals are to (1) develop and test the acceptability, feasibility, and preliminary efficacy of a randomization of NA-PT versus CBT-E and (2) to test if network-identified precision targets are the mechanism of change. These goals will ultimately lead to the very first personalized treatment for ED and can be extended to additional psychiatric illnesses. The proposed research uses highly innovative methods; intensive longitudinal data collected with mobile technology is combined with state-of-the art idiographic modeling methods to deliver a virtual, personalized treatment. Specific aims are (1) To collect preliminary data on the feasibility and acceptability of the randomization of NA-PT (n=40) for EDs versus CBT-E (n=40), (2) To test the initial clinical efficacy of NA-PT versus CBT-E on clinical outcomes (e.g., ED symptoms, body mass index, quality of life) and (3) To examine if changes in NA-identified, precision targets, as well as in dynamic network structure, are associated with change in clinical outcomes. The proposed research has clinical impact. Ultimately, this proposal will lead directly to the creation and dissemination of an evidence- based personalized treatment for EDs, as well as will serve as an exemplar for personalized treatment development across the entire field of psychiatry.