A Pilot Randomized Control Trial of a Relapse Prevention Online Exposure Protocol for Eating Disorders and Mechanisms of Change - PROJECT SUMMARY/ABSTRACT Eating disorders (EDs) are chronic and disabling; most individuals never achieve full remission, even after intensive treatment, and 50% of those who access intensive treatment will relapse within 6-months of discharge. These high relapse rates occur often and contribute to the poor outcomes seen in EDs. Importantly, existing treatments to not differ from control treatments in the ability to alter cognitive ED pathology, which is the primary remaining symptomatology at discharge from intensive care. ED relapse-prevention treatments are urgently needed that can disrupt the persistent cycle of admission and discharge from intensive treatment and that are explicitly targeted at core cognitive-affective pathology. Our scientific premise, developed from our past work, is that the application of an online exposure protocol will engage fear extinction - improving outcomes, enhancing full recovery, and decreasing the likelihood of relapse. Our study goals are to (1) develop and test the acceptability, feasibility, and preliminary efficacy of a randomization of an online exposure relapse-prevention protocol that can be delivered post- acute treatment versus a writing control treatment and (2) to test if this treatment targets fear extinction, which is a core aspect of ED cognitive-affective pathology. These goals will ultimately lead to a highly deployable and accessible online treatment targeted at core ED mechanisms. The proposed research uses highly innovative methods; we will use an all remote technology- based approach, combining an online treatment with mobile technology that assesses the target of fear extinction. The combination of an online treatment with mobile assessment allows, for the first time, the creation of an engaged and targeted treatment, which can rapidly be disseminated during a critical period of care. Specific aims are to (1) collect preliminary data on the feasibility and acceptability of the randomization of two treatment conditions after discharge from intensive ED treatment: a relapse-prevention online exposure protocol (n=65; ROEP) and a control treatment writing condition (n=65) (2) To test for differences between ROEP and control treatment for the prevention of relapse and preliminary change on clinical ED outcomes (3) To examine if ROEP targets fear extinction and if fear extinction is associated with relapse and ED outcomes, and (3b) To test if baseline differences in fear conditioning relate to change in ED outcomes across treatment. The proposed research has clinical impact. Ultimately, this proposal will lead directly to the creation and dissemination of a highly user-friendly, easily accessible and deployable intervention that can prevent relapse in the EDs, which will decrease mortality, morbidity, and the high costs associated with chronic treatment.