PROJECT SUMMARY SKILLS TO ENHANCE POSITIVITY IN ADOLESCENTS AT RISK FOR SUICIDE Rates of suicide and suicidal behavior in adolescents have been steadily increasing over the past two decades. Unfortunately, reviews of published randomized controlled trials (RCTs) for adolescent suicidality conclude that treatments to date have been minimally efficacious, particularly when compared to adult trials. The preponderance of interventions focus on crisis intervention, underling psychiatric disorders, regulating negative affect, and reducing cognitive distortions. However, our pilot work and other recent data suggest the importance of considering how low positive affectivity may be a mechanism that contributes to suicidal behaviors independent of other risk factors. Therefore, we developed an intervention, Skills to Enhance Positivity (STEP; MH R34101272), premised on the Broaden and Build theory of positive affect, to increase attention to, and awareness of positive affect and experiences. Results from our pilot RCT (N=52) with inpatient suicidal adolescents found that compared to a Healthy Habits / Enhanced Treatment as Usual (ETAU) condition, those randomized to STEP had 50% fewer individuals reporting a suicidal event, 50% fewer suicidal events overall, and a larger decrease in participants reporting active suicidal ideation (SI) over follow up (49% STEP vs. 19.2% ETAU). STEP also appears to have engaged the target mechanism as STEP participants had faster reaction times to positive probes on an attentional bias task compared to ETAU, and only those in the STEP condition reported significant pre-post differences on gratitude and satisfaction with life. These promising results in which we were able to demonstrate engagement of the target (positive affect) and a decrease in clinical outcomes (suicidal events) suggest the need to test the clinical effectiveness of STEP by having clinical staff implement the intervention. Furthermore, recognizing the need to speed translation, we propose a Hybrid Type I Effectiveness-Implementation design. Specifically, we propose to test the effectiveness of STEP in reducing suicidal events and ideation in 216 adolescents, admitted to inpatient psychiatric care due to suicide risk. Participants will be randomized to either STEP or ETAU. STEP involves 4 in-person sessions (3 individual, 1 family) focused on teaching psychoeducation of positive and negative affect, mindfulness meditation, gratitude, and savoring. Digital health messages with mood monitoring prompts and skills reminders will be sent daily for the first month post-discharge and three times a week for the following two months. ETAU condition will receive daily reminders to log into a safety resource app. We hypothesize that those randomized to STEP (vs. ETAU) will have less suicide events, ideation, and depression, and experience increased positive affect and attention to positive affect, and decreased negative affect, and attention to negative affect, as me...