PROJECT SUMMARY/ABSTRACT Suicide is the second leading cause of death among individuals aged 10-34 in the US, with 17% of high school-aged youth seriously considering a suicide attempt and 8% attempting suicide. There is emerging evidence to suggest that preventive interventions that do not explicitly target suicide have “crossover” effects on suicidality. However, the majority of interventions that have been examined for their impact on suicide target internalizing behaviors, which may miss a significant subset of boys, whose risk for suicidality is primarily transmitted through externalizing; this concern is echoed by calls in the recent suicide prevention literature for addressing the dearth of literature on suicide crossover effects from externalizing-focused interventions. The Coping Power (CP) program is an empirically supported, child- and family-focused preventive intervention that focuses on reducing externalizing more broadly among youth who exhibit early aggression, which makes it ideally suited to addressing the above-mentioned gaps in targeting externalizing pathways to suicidality. The proposed study will combine data from 10 randomized controlled trials (RCTs) of CP (total individual-level N = 3,201; total school-level N = 188) and utilize three measurement and data analysis frameworks that have emerged across multiple independent disciplines: integrative data analysis (IDA), meta- analysis of individual patient data (MIPD), and propensity score weighting (PSW). Using these frameworks, we propose the following aims: Aim 1: Estimate scale scores for key constructs while accounting for differential item functioning across studies, time, populations, and reporters. Aim 2: Assess comparative effect sizes for multiple forms of Coping Power (CP) using IDA-estimated scale scores for CP mechanisms of action, externalizing, internalizing, and suicidality. Aim 3: Test for potential mediators of CP effects on risk for suicidality as transmitted through CP's mechanisms of action (MoAs) and/or intermediate endpoints. Aim 4: Explore individual-, school- and study-level moderators of CP's effects on MoAs, intermediate endpoints, and risk for suicidality. If successful, the proposed study will (1) be one of the first to apply a symptom weighting framework (e.g., MNLFA, item response theory) for measuring suicidality, while accounting for measurement bias across multiple factors (e.g., time, development, demographic variables, reporters), (2) provide initial evidence for preventive effects on suicidality through gender-specific pathways (externalizing for boys, internalizing for girls), (3) illustrate evidence that CP's direct and/or indirect impact on reductions in suicidality is greater among youth who are at higher initial risk, and (4) identify the optimal conditions for CP delivery (e.g., group, individual, internet) for different youth characteristics (which could not be examined in any single RCT of CP).