Recent research suggests that more than 60% of adults with bipolar disorders experience the first onset of their illness prior to age 18. Early onset of bipolar disorder is a risk factor for more severe course (e.g., more frequent episodes, greater comorbidity, greater suicidality) over lifetime. Moreover, adolescence is a period of normative changes in reward-relevant brain structures and reward processing, i.e., functioning of behavioral approach system (BAS). However, relatively little is known about mechanisms leading to bipolar disorder symptoms during adolescence. This project examines what in the normative development of reward processing/BAS functioning goes awry in adolescents with bipolar disorders. A variety of measures are used including task-based functional as well as structural magnetic resonance imaging (MRI), behavioral tasks, and self-report measures. Furthermore, the project aims to identify the specific BAS functioning indices that can predict prospective changes in bipolar symptom severity during adolescence and the course of illness over time. This project has been funded by the National Institute of Mental Health, K01 MH093621, awarded to Snežana Urošević.