RecruitingBehavioural interventionExercise Facilitation of Adolescent Fear Extinction, Frontolimbic Circuitry, and EndocannabinoidsAnxiety disorders commonly begin during adolescence, and are characterized by deficits in the ability to inhibit or extinguish pathological fear. Recent research has provided new understanding of how fear is learned and can be regulated in the adolescent brain, and how the endocannabinoid system shapes these processes; however, these advances have not yet translated into improved therapeutic outcomes for adolescents with anxiety. This study will test whether a behavioral intervention, acute exercise, can help to improve fear regulation by enhancing brain activity and endocannabinoid signaling. This line of research may ultimately lead to more effect treatments for adolescent anxiety, and to new preventive strategies for at-risk youth.