PROJECT SUMMARY Depression in youth is a recurrent and impairing disorder. Although some treatments have shown modest effects in children and adolescents [e.g., cognitive behavior therapy (CBT)], there remains a critical need to improve upon these therapies in order to reach even more youths with depression. One variable hypothesized to affect children’s interpersonal relationships, as well as how well they learn the skills taught in CBT, is their level of social cognitive development on abilities particularly relevant to social functioning and to CBT (e.g., social perspective taking, theory of mind). The first phase (R61) of the proposed project will test whether a novel intervention that aims to increase children’s social cognitive (SC) abilities (the “target”) will improve children’s SC skills, and also their uptake of the strategies taught in CBT (e.g., cognitive reappraisal), with the goal of reducing levels of depression. Youths (ages 12-17; N=42) with depression diagnoses or clinical levels of depressive symptoms (CESD ≥ 20) and a deficit in the targeted SC skills will be randomly assigned to either the social cognitive training enhanced CBT (SCT-CBT) or to a usual care (UC) comparison condition. Pre- and post- treatment evaluations will assess the target (e.g., social cognitions) and depression. “Target” engagement will be defined as a medium effect size (≥.40) in the comparison of SCT-CBT vs. UC on the target SC measure at post-test, controlling for pre-test level of SC. We also will assess the target after sessions 3 and 6 to examine dose (i.e., at what point the target is reached). In the second phase (R33), we will conduct a replication trial with a new sample of 82 youths (ages 12-17) again randomized to either SCT-CBT or usual care. Youth will be evaluated with regard to the target SC abilities, as well as their knowledge of CBT skills, level of depressive symptoms, and social functioning at baseline and post-intervention (R61 and R33), and at a 4-month follow-up (R33). All analyses will control for age, sex, and IQ. Finally, in the R33 we will test for mediation – that increases in SC abilities partially account for the relation between Condition (SCT-CBT vs. UC) and decreases in depressive symptoms, and also between Condition and increases in CBT skills. If the SCT-CBT intervention significantly improves children’s SC abilities, increases their capacity to uptake CBT strategies, decreases their depressive symptoms, and improves their social functioning, then this will provide therapists with a more efficient and personalized treatment of depression, and thereby substantially improve clinical care.