Project Summary Suicide is an alarmingly common cause of death for people living with psychosis. Conservative estimates suggest that at least 5% of people with psychotic spectrum disorders complete suicide, accounting for approximately 11% of suicides worldwide or nearly 100,000 suicides each year. The absolute risk of suicide remains high even for people who are engaged in specialty psychosis treatment, and interventions that have been designed specifically to prevent suicide in people with psychosis have shown limited impact. One important suicidogenic factor for people with psychosis is emotion dysregulation, which is the failure to regulate emotion resulting in problematic emotional states. Emotion dysregulation is a core feature of psychotic disorders and yet this factor is commonly neglected in treatments provided to this population. Research has shown that emotion dysregulation is closely linked to suicide in people with psychosis and emotion regulation is a primary target of some of the best-established and most effective psychosocial interventions for suicidality in other populations, most notably Dialectical Behavior Therapy (DBT), but relevant clinical trials routinely exclude people with psychosis. The goal of this K23 is to conduct a prepilot and pilot randomized controlled trial of group DBT skills training (DBT-ST), an intervention that targets emotion regulation, in a sample of people with psychosis and heightened suicidality. This pilot study would allow us to determine feasibility, acceptability, and obtain preliminary estimates of the impact of DBT-ST on key outcomes. A critical component of this work is the use of a rigorous methodology for measuring emotion dysregulation. Such measurement has seen advances in recent years in the form of ecological momentary assessment (EMA) which enables the direct statistical modeling of emotion dysregulation without reliance on retrospective self-report. To further increase rigor and reproducibility, we propose to pair such ecological measurements with qualitative assessments of participant experiences of EMA data collection to aid in the construction and interpretation of sophisticated statistical models of emotion dysregulation in psychosis that account for non-random missingness as well as exogenous variables that may confound measurement of the impact of DBT on emotion dysregulation. This mixed methods approach will allow us to better assess how DBT-ST might improve emotion regulation in people with psychosis. The proposed study will pave the way for a larger trial evaluating whether treatment of emotion dysregulation can decrease suicide risk in psychosis. The above research proposal will be carried out within the University of Maryland Division of Psychiatric Services Research—an institution with a strong track record of successful clinical trials research with people with serious mental illness—and will be paired with mentorship and training in the areas of (1) the conduct of experim...