This project responds to the need for (1) scientifically rigorous evaluations of interventions to prevent suicide in adolescents, and for (2) school-based suicide prevention programs that are suitable for rural and underserved communities where there is a scarcity of mental health services. Suicide accounts for more deaths among 10 - 24 year olds in the US than all natural causes combined;each year 5 - 9% of adolescents attempt suicide and 700,000 require medical attention. In most rural regions, adolescent suicide rates are 2 - 10 times above the US national average. This proposal seeks RO1 funding for a randomized controlled trial to evaluate the effectiveness of the Sources of Strength (SoS) intervention in reducing rates of attempted suicide among adolescents in rural communities. SoS builds social-ecological protective influences across a full population of high school students to reduce the likelihood that vulnerable youth will become suicidal and connects suicidal youth to capable adults at school and in the community. Trained 'peer opinion leaders'change the norms of students throughout their schools regarding the acceptability of suicide, help-seeking and youth-adult communication by conducting a set of well-defined messaging activities with ongoing adult mentoring. This approach draws on the major influence of adolescent peers that is powerful enough to affect drug use, sexual practices and other health behaviors. We have completed work to prepare SoS for a large scale trial, including conducting a preliminary study using a randomized design in 18 schools showing that the intervention modifies the norms of students school-wide about suicide and help seeking, with the largest changes occurring among suicidal youth. For the proposed 5-year study, 36 rural high schools in New York and North Dakota will be randomly assigned to immediate SoS or wait-list control conditions. We will survey students in the schools over 18 months to (1) compare intervention and control levels of self-reported suicide attempts, (2) determine differences in impact for low- and high-risk groups, (3) test multiple hypothesized mediators of SoS impact on reducing suicide attempts from our intervention causative model, (4) use social network methods in a subset of schools to identify network mediators of SoS impact, the extent of dissemination of peer-to-peer messages, and evaluate the efficiency of the current strategy for identifying student peer leaders. This project can have a positive public health impact through the potential to prepare a cost-effective intervention that can be implemented safely in diverse communities and is effective in reducing suicidal behaviors among adolescents. PUBLIC HEALTH RELEVANCE: This proposed 5-year project can have a positive public health impact by preparing Sources of Strength (SoS), a school-based suicide prevention intervention, for expansion as a cost-effective program that can be implemented safely in diverse communities and is effective in reducing suicidal behaviors among adolescents. The proposed study can also contribute to knowledge needed to strengthen social-ecological protective influences across a full population of high school students by peer opinion leaders to change the norms of students through their schools and reduce suicidal behaviors.