Project Summary/Abstract Suicide is the 10th leading cause of death in the United States and has increased by 35% in the last two decades. Emergency Departments (EDs), often serving as the only clinical contact for individuals at risk for suicide, are a critical point for initiating suicide prevention interventions. Limited availability of psychiatric beds and challenges with linking to, or sustaining, post-ED care exacerbate the already heightened risk for suicidal behavior among discharged individuals. Best-practice guidelines for EDs recommend providing individuals at elevated suicide risk with brief interventions that include safety planning—emphasizing coping strategies to mitigate suicidal crises—as well as post-discharge contacts, however busy EDs often lack adequate resources to offer these interventions consistently or with fidelity. New approaches that can provide accessible, personalized, and resource-efficient continuity of care are urgently needed to prevent suicidal behavior during the high-risk post-ED period. Leveraging accessible technologies, we propose to develop and pilot an ED- initiated intervention package that incorporates an electronic safety plan (ESP) and adaptive text-based support to facilitate effective post-discharge coping and safety plan use, and ultimately reduce suicidal behavior in high-risk adults. Adults presenting to an ED for suicide-related concerns (N=120) will be randomized to ESP (n=40) or ESP + text-based support program (n=80) delivered for a month after discharge. The ESP + text-based support condition will include an embedded micro-randomized trial (MRT), with twice- daily randomizations over the month-long intervention, to optimize the frequency, timing, and content of messages and to inform the design of a just-in-time adaptive intervention (JITAI) for suicide prevention. Follow- ups will occur at 1 and 3 months, as well as twice-daily for the first month after discharge. The specific aims are to: (1) Develop and refine ESP and text-based support with stakeholder input; (2) Demonstrate feasibility, acceptability, and explore initial impact on mechanisms (coping self-efficacy, motivation for safety plan use) and distal outcomes (e.g., suicidal ideation severity), assessed at 1 and 3 months, for ESP with text-based support compared to ESP alone; and (3) Conduct a pilot MRT to inform the optimization of adaptive text-based support (JITAI). Specifically, through the series of micro-randomizations, we will explore if provision of (a) any coping message, (b) a specific type of coping message (untailored vs. ESP-tailored; with or without dynamic personalized feedback based on daily-level functioning), and (c) message timing (e.g., morning vs. evening) influence daily-level proximal mechanisms (e.g., safety plan use, coping behavior, self-efficacy) and distal outcomes (suicidal ideation). With potential for high public health impact, this proposal addresses a critical need for effective and scalable continuity of care during the high-risk post-ED period to improve suicide-related outcomes. The impact of the proposed intervention will be strengthened by stakeholder input to inform future implementation, and tailored remote delivery that can be integrated with existing health system technologies.

PROJECT NARRATIVE The proposed project will address a critical need for effective and scalable intervention approaches for adults presenting with suicide-related concerns to Emergency Departments (EDs), many of whom remain at high risk for suicidal behavior following ED discharge. Using a two-arm randomized controlled trial with an embedded micro-randomized trial (MRT), the project will obtain key data on feasibility, acceptability, and initial impact on hypothesized mechanisms to inform an effective technology-augmented intervention package, including ED- initiated safety planning and adaptive post-discharge text messages. Findings from this study will provide the necessary groundwork for a scalable and resource-efficient intervention targeting reduction in suicidal behavior during the high-risk transition after ED care.