Pediatric anxiety and Obsessive Compulsive Disorder (OCD) are prevalent and impairing, yet a significant subset of youth who receive the first-line treatment (Cognitive Behavioral Therapy; CBT) will not experience symptom remission. Youth with anxiety and OCD report high rates of sleep problems; evidence suggests that self-reported sleep-related problems predict slower improvement and poorer clinical outcomes in exposure-based CBT. Gaps in knowledge remain about the role of sleep for therapeutic learning during CBT treatment. This project aims to address these gaps by integrating multi-method sleep assessments with fear extinction learnings, which is one of the presumed mechanisms of action in CBT for anxiety and/or OCD. The research objectives are to characterize sleep problems in a sample of youth with anxiety and/or OCD and examine the association between sleep variables and psychophysiological measures of fear extinction learning. The central methodology involves multi-method sleep assessments including self-report measures, actigraphy, and night time electroencephalography, and a computer-based fear extinction learning task, which includes measuring skin conductance responses (SCR) in 84 adolescents (age 13-17) with primary anxiety or OCD entering a CBT-based intensive outpatient program. The central hypothesis is that shorter sleep quantity and greater sleep disruption are associated with psychophysiological responses indicating reduced fear extinction learning and reduced fear extinction recall in adolescents with anxiety and OCD. This project is innovative in that the use of multi-method sleep assessments in a clinical sample of youths with anxiety and/or OCD is novel. In addition, linking sleep measures with psychophysiological indexes of fear extinction learning in a clinical sample of youths has not yet been done, to our knowledge. Future research will investigate these associations with repeated measurement across a full course of CBT treatment. If successful, we will be poised to develop and test augmentation strategies that target specific aspects of sleep that contribute to sub-optimal fear extinction learning. Ultimately, results from this work may serve as proof-of-concept for identifying sleep targets to guide the augmentation of behavioral treatments for anxiety and OCD.