Project summary/abstract Training programs in psychiatric epidemiology are increasingly critical to advance science and develop prevention and intervention efforts that positively affect public health. The events of 2020 brought into stark focus the economic, geographic, educational, and racial inequalities in the US that deeply affect mental health and wellbeing. They deepen the need to consider how the social environment and psychiatric disorders intersect with biological determinants of health, for which new data sources and technology are rapidly accelerating, and to plan for strengthening of public mental health infrastructure. Changes in recent years in the incidence and prevalence of psychiatric disorders, and accelerating data collection and technological capacity, are impacting how psychiatric research is conceptualized, research participants are recruited, and mental health data are analyzed across research domains, and these factors will inform how mental healthcare is delivered, accessed, and evaluated. Since 1972, the Columbia Psychiatric Epidemiology Training (PET) program has produced productive scientists who emerge as leading voices on how to assess etiology, epidemiology, biology, and intervention in mental health scholarship and services to respond to emerging needs. We believe that the success of this program is due to five foundational features: 1) training in theory- and hypothesis-driven scientific inquiry; 2) interrogation of multiple levels of causation with dynamic interactions; 3) development and application of methods for prediction and causal inference; 4) responding to changes in public health and mental health; and 5) training and research in ethical principles that underpin work with disadvantaged populations such as those with mental disorders. In the next five years of our program, we will continue to grow each of these areas through scholarship and training. Our focus has drawn scholars from numerous disciplines to engage with our faculty, coursework, and training—scholars who then become leaders with impact across academic and non-academic settings assessing social and biological psychiatry, service equity and delivery, and designing and evaluating evidence-based treatments. These scholars are better informed and their workforce better situated to significantly impact science and practice when trained to interrogate multi-level frameworks, causal inference, and the ways in which social factors influence etiology, diagnosis, and access to systems of care. Over the next stage of growth of the PET program, we will build upon these foundations with additional faculty, training, and expertise. By balancing growth of historical legacies and new intellectual resources, the PET program will be poised to prepare the next generation of scholars and change-makers to address critical challenges among those with mental illness across the globe. Epidemiologists trained by the PET program have the skills necessary to strength...