PROJECT SUMMARY This application establishes a new T32 training program in embedded mental health services research in health systems leveraging the resources of the NIMH-funded Mental Health Research Network (MHRN). MHRN is a consortium of 21 health systems across 16 US states serving more than 30 million patients per year. Established in 2010, the network provides unique data infrastructure via a common data model, including all electronic health records, insurance claims and administrative records organized using the same variables and data definitions across sites enhancing efficient mental health services research. Importantly, each of the MHRN health systems includes embedded research centers with experienced mental health services researchers with long histories of NIMH funding. MHRN is a practice-based research network leveraging close relationships between these embedded scientists and health system leaders, clinicians, and patients to facilitate an iterative research-practice-policy ecosystem focused on studying key mental health clinical and research questions. This strong relationship drives mental health care transformation. The proposed program will include 2 MHRN health systems serving as postdoctoral training host sites, Henry Ford Health System (Michigan) and Kaiser Permanente Northern California, and provide access, data, and resources across all MHRN sites. This T32 will support 10 total postdoctoral fellows for 2-year training programs during the 5-year award period. The program will use a novel training approach with virtual and in- person training and mentorship embedded within the established infrastructure across the entire MHRN. The program will integrate an external University-based faculty advisory committee and additional external senior scholars. The program is interdisciplinary and expects to recruit doctoral-level trainees from many disciplines. The core training and mentorship model will include the following aims for all postdoctoral trainees: 1) Didactic training in health services research methods and mental health disorders etiology, prevention, and treatment tailored for embedded health system research settings, 2) Individualized training and mentorship in grant writing, dissemination, project management and leadership, professional development, and multi-site study collaboration and coordination, and 3) Participation in all applicable MHRN health system activities. Our long- term goal is producing independent scientists, who can engage in practice-based research through the pursuit of early career funding opportunities for mental health services research.