PROJECT SUMMARY/ABSTRACT Over half a million people in the U.S. present annually to Emergency Departments (EDs) for suicidal ideation (SI) and/or suicidal behavior (SB). After leaving the ED, their short-term risk of repeated self-harm and death by suicide are exceptionally high. Individuals with autism spectrum disorder (ASD) are disproportionally represented among those seen in the ED for suicide-related emergencies. Individuals with ASD are up to nine times more likely to experience SI and up to five times more likely to attempt suicide than the general population. Despite their increased risk for suicide and high rates of suicide-related ED visits, little is known about the experiences or outcomes of suicidal individuals with ASD seeking emergency care. The proposed mixed methods study will contribute to long-term efforts to reduce deaths by suicide by informing the adaptation and implementation of evidence-based practices for suicide prevention for individuals with ASD. The study objectives are: (a) to use a retrospective, longitudinal design to compare the experiences and outcomes of individuals with and without ASD who sought care for SI or SB in EDs nationwide; and (b) to interview key stakeholders about ways to improve ED-based suicide prevention practices and increase post-ED mental health treatment engagement for individuals with ASD. Claims records from over 100 million publicly- and privately-insured individuals will be used to ascertain and follow a diverse national cohort of patients with a suicide-related ED visit. Hospital- and county-level information will be drawn from the American Hospital Association Annual Survey Database, SAMHSA National Survey of Mental Health Treatment Facilities, and Area Resource File. Outcome variables include ED discharge disposition, outpatient mental health service utilization, SI or SB recurrence, and death by suicide (from the National Death Index). Semi-structured interviews with individuals with ASD and suicide-related ED visits, their family members, and ED physicians will elaborate upon the quantitative findings and inform potential targets for future ED-based intervention and implementation strategies. Results will help policy makers and healthcare workers across the U.S. to better understand critical points of prevention and intervention for suicidal individuals with ASD. This project is well- aligned with the Interagency Autism Coordinating Committee's objective to reduce disabling co-occurring mental health conditions and premature mortality in people with ASD, and NIMH's Strategic Objective 4 focused on strengthening the public health impact of NIMH-funded research.