PROJECT SUMMARY / ABSTRACT This career development proposal will support Dr. Enrico Castillo to become an independent researcher focused on serious mental illness (SMI), incarceration, homelessness, and public mental health systems, with expertise in conducting mixed methods studies to improve the capacity of public systems to eradicate the health and social inequities experienced by individuals with SMI. People with SMI experience severe inequities, which are particularly evident within homeless populations and correctional facilities where people with SMI are grossly overrepresented. These national challenges are reflected in Los Angeles County, which has the largest unsheltered population of people with SMI in the US. The Los Angeles County jail is the largest facility in the world for the confinement of people with SMI. In the face of scarce public mental health resources and concentrations of people with mental illness in jails, some have posited that jails may serve important public health functions and have positive mental health effects on individuals with SMI. This raises important scientific questions. Dr. Castillo plans to focus his research on understanding the unmet health and social needs of individuals with SMI by studying the effects of incarceration on subsequent health and social trajectories—the jail-to-homelessness pipeline. Dr. Castillo’s proposal centers on mentored career development and research activities that will develop the skills to achieve these career goals: 1) quantitative analysis of linked administrative data, 2) qualitative research methods, specifically ethnography, archival research, and mixed methods dialogue, 3) criminal justice systems and vulnerable justice-involved populations, and 4) dissemination and translation of health services research findings to policy and practice. Given the challenges of studying individuals after jail release, relatively less is known about the precise relationship between incarceration and subsequent homelessness and its downstream effects on healthcare and social trajectories for people with SMI. Fragmented systems of care and siloed data infrastructures are additional barriers to research, coordination of care, allocation of resources, and public health planning. To address these lacunae, Dr. Castillo’s research project will 1) use an existing linked administrative database of eight public service agencies in Los Angeles County to understand whether jail is disruptive to mental health and social service use and housing stability for people with SMI; 2) conduct archival research and direct ethnographic observations in the Los Angeles County jail to elucidate the jail experiences and services and ascertain the mechanisms underlying post-incarceration trajectories; and 3) prepare for a R01 health services research grant (PAR-17-264). Building on this project’s findings about factors that lead to post-incarceration homelessness, that future multi-site R01 will employ the same mi...