PROJECT SUMMARY/ABSTRACT The rates of suicide and suicidal ideation and behaviors (SIB) among Black youth have increased drastically in the past decade, with the rate of suicide rising from 2.55 per 100,000 to 4.82 per 100,000 from 2007 to 2017. As compared to their White counterparts, the risk of suicide for Black youth under 13 years old has doubled in the same time period. The overarching goals of this study are to improve our understanding of the uniqueness and complex etiology of Black youth suicide and SIB through a multi-dimensional approach and to provide valuable information for future policies targeting suicide reduction among the Black youth population. To do so, I will first identify risk and protective factors for Black youth (aged 10-24 years) suicide and SIB by jointly considering individuals’ medical history, neighborhood-level social integration level, and the geographic distributions of neighborhoods and suicide rates. A large electronic health records (EHR) database from multiple healthcare systems across New York City (NYC) will be used so that I can gather enough cases of Black youth suicide and SIB along with their clinical data. Secondly, more culturally sensitive theories are needed to explain the underlying mechanism driving Black youth suicide and SIB. Suicide and SIB tend to cluster in geographic space. Prior research using US county-level mortality data has found that the geographic clustering of suicide rates is affected by both social integration and imitation. Durkheim's social integration theory suggests that the more socially integrated a person is, the less likely one is to end his/her life. Tarde’s imitation theory explains suicide as a result of humans adopting the beliefs and behaviors of others in neighboring areas, suggesting suicide as a contagion. Both the social integration and imitation theories have been tested on the general youth population as well as the aboriginal and Inuit youth population. However, whether they can explain contemporary Black youth suicide and SIB is yet to be evaluated. I will develop a composite measure to quantify neighborhoods’ social integration level, which will be used to evaluate the social integration theory along with the imitation theory on the Black youth population. Finally, the counterfactual effects of these social factors on Black youth suicide and SIB risk reduction will also be evaluated. The proposed study addresses an important public health crisis and the completion of the study will inform the design of social and clinical policies that have greater efficiency in reducing the rates of Black youth suicide and SIB. Given the array of new competencies and the multidisciplinary nature of the proposed work, this K99/R00 award is a necessary step to achieve the candidate’s career goal of leading an interdisciplinary team committed to closing the gaps of youth mental health disparities.