ABSTRACT Suicide rates among Hispanics in the United States have increased in the last two decades; coupled with rapid growth of the Hispanic population, suicide among Hispanics is a pressing public health issue. Considering the role of culture in suicide can elucidate unique and modifiable mechanisms for suicide. The Candidate’s long- term research goal is to optimize suicide prevention interventions for Hispanics by targeting cultural determinants of health. Reaching that goal requires mentored training in three domains of suicide prevention research and completion of a research project to produce substantive, foundational results (described below). First, the candidate needs to gain expertise in randomized clinical trials methodology for suicide interventions (Objective 1) to conduct a trial with at risk Spanish-speaking adults in a reliable, valid, and ethical manner, and test target engagement with an experimental therapeutics approach. Second, the candidate needs to gain expertise in optimizing behavioral interventions to impact cultural determinants of health via human-centered design (Objective 2) to deliver a treatment protocol that is culturally-usable and optimized to increase cultural- social engagement. Third, as smartphone technology increases precision to measure mechanisms, the candidate needs to gain expertise in the use of novel smartphone technology for precise assessment of target engagement in clinical trials (Objective 3) to optimally/ethically use this technology in clinical trials research. The principal objective of the proposed research study is to use an experimental therapeutics approach to examine whether a behavioral intervention (SOCIAL ENGAGE; S-ENGAGE) can increase cultural-social engagement (intervention target) and decrease suicide risk (clinical outcome) among Hispanic adults. First, human-centered design approaches will be used to iteratively refine and optimize S-ENGAGE to alter cultural-social engagement via iterative feedback from 5 Spanish-speaking adults with low cultural-social engagement and recent ideation. Second, 60 Spanish-speaking adults who report low cultural-social engagement and recent ideation will be randomized into 10-weeks of S-ENGAGE or an expectancy-matched control. Participants will provide 2-weeks of real-time data via smartphone at baseline, post-treatment, and 3- month follow-up and complete semi-structured interviews. Research Aims are to: (1) Optimize S-ENGAGE for target engagement. (2) Test target engagement: Does S-ENGAGE increase cultural-social engagement among Spanish-speaking adults?; (3) Test clinical impact: Does S-ENGAGE decrease suicide risk among Spanish-speaking adults?; (4) To contextualize findings: What components of S-ENGAGE were most helpful? The resulting findings of this K23 project will function as the basis for a larger R01-funded study powered to examine whether the proposed target (cultural-social engagement) leads to changes in the clinical outcome (suicide i...