Background: This fellowship application is from a 4th year clinical health psychology PhD student studying HIV, syndemic theory, and behavioral health in international settings. The research component takes place in S. Africa, which has the highest number of HIV/AIDS cases globally,1 a high prevalence of comorbid mental health problems with HIV, and where structural problems (e.g., food insecurity2, poverty3) interact with mental health and further contribute as barriers to HIV care. Few studies have examined the effects of syndemics among people with HIV (PWH), where outcomes such as adherence and viral suppression are important. In addition, none have done so in S. Africa, where drop-offs in the treatment cascade are common,4 and only first and second line ART regimens are easily available. Research Strategy: This fellowship would be the first to examine effects of psychosocial and structural syndemic problems on HIV viral load and engagement in care (i.e., HIV treatment retention and adherence assessed through pharmacy refill) among PWH receiving care at public primary care clinics in S. Africa (N=175). Linked to a carefully considered training plan of mentoring, coursework, and workshop experiences, the research project will advance the candidate’s trajectory of becoming an independent investigator in HIV, syndemic theory, and global mental health. It will leverage an existing NIMH R01 (PIs: Safren/O’Cleirigh, R01MH103770) studying patients receiving HIV care at primary care clinics in Khayelitsha, a peri-urban settlement outside of Cape Town, S. Africa. The parent study assesses clinic patients for psychosocial and structural conditions, and other behavioral variables. Accordingly, the following aims are proposed. Aim 1 will innovatively examine the interrelationships between syndemic problems via network analysis. This will allow for developing hypotheses about how these syndemic indicators specifically interact, potentially a methods breakthrough in the literature on how to best analyze syndemic interactions. Aim 2 will estimate both the additive and interaction effects (specified based on the pattern of interrelationships between syndemic problems in aim 1) of syndemic problems on engagement in care and viral load over 12 months. Lastly, Aim 3 (exploratory and tied to biostatistical training) will examine, using structural equation modeling, whether engagement in care over one year mediates the effects of syndemic problems at baseline on viral load at 12 month follow-up. Training Plan: The training plan will allow for acquisition of the necessary skills, through formal coursework and individual meetings, to employ advanced and novel statistical and assessment methods to examine the effects of syndemic problems on HIV outcomes over time. The training plan also serves as the foundation for the next steps (e.g., K23) in creating a research program to improve mental health and HIV outcomes among PWH globally and domestically. Next Steps: The ...