Bullying, or peer victimization, is a particularly salient stressor that affects over 5 million adolescents in the US every year, regardless of ethnicity, gender, or socioeconomic status. During adolescence, when concerns with fitting in and gaining peer approval are heightened, experiences of peer abuse can elicit emotional distress and fear of continued harassment. Indeed, work by MPI Schacter and others implicates peer victimization as a unique prospective risk factor for anxiety during adolescence and indicates that chronic victims are two to three times more likely to develop an anxiety disorder than their nonvictimized peers. Moreover, whereas overt (i.e., physical or verbal) victimization becomes less frequent as children get older, relational victimization (i.e., damage to social relationships) remains common and becomes increasingly emotionally taxing during adolescence. Despite the strong and pervasive link between relational peer victimization and the development of anxiety during adolescence, little is known about the underlying psychobiological mechanisms that account for and maintain such associations. Given that stress-related biological alterations can predate mental health problems and current treatments for anxiety are costly and intensive, it is crucial to identify malleable therapeutic targets that can mitigate the emotional toll of peer trauma. The proposed R21 will evaluate threat sensitivity as a potential target for the prevention and treatment of anxiety in peer victimized youth. The project will be the first to examine the unique effects of peer victimization on physiological responses to threat during adolescence and evaluate the prospective effect of aberrant threat sensitivity on adolescent anxiety. In particular, we predict 1) compared to less victimized adolescents, more frequently victimized adolescents will exhibit an exaggerated physiological response to potential threat during two validated tasks; 2) heightened physiological threat responses will prospectively predict adolescent anxiety. MPI Marusak and co-I Jovanovic have used these approaches in other pediatric populations in previous and ongoing studies, and have demonstrated that threat biases (i.e., heightened arousal to potential threat) partially stem from childhood adversities, such as being the target of familial abuse or neglect. However, the proposed study will be the first to examine prospective associations among peer victimization, physiological markers of threat sensitivity, and anxiety in adolescents. This novel line of work will directly inform future investigations examining threat sensitivity as a mechanism and provide initial support for threat sensitivity as an important diagnostic tool to 1) identify peer victimized youth who are at the greatest risk for developing anxiety and may benefit from cognitive bias modification or other threat sensitivity reduction approaches, and 2) inform the design and modification of developmentally sensitive ...