PROJECT SUMMARY/ABSTRACT Nonsuicidal self-injury (NSSI) affects an estimated 17% of adolescents worldwide. Earlier onset in adolescence is linked to more severe trajectories of NSSI, suicide plans, and poorer quality of life. Though early intervention for NSSI is critical, most adolescents with NSSI do not seek professional help, and many do not self-disclose their behaviors to anyone in person, limiting access to support and preventing pathways to treatment. While several psychological interventions have been effective in reducing adolescent NSSI, structural barriers (e.g., time, cost), attitudinal barriers (e.g., stigma, mental health literacy), and the prevalence of non-disclosure constrain their accessibility and reach. Digital mental health interventions (DMHIs) present an opportunity to reach this high-risk and non-treatment-engaged population and increase their access to evidence-based psychological strategies. Indeed, adolescents report receptivity to digital interventions and engage in NSSI help-seeking online at high rates. However, to date there are no publicly available DMHIs designed to support this adolescent population. In collaboration with Mental Health America (MHA), the nation’s largest mental health advocacy organization, the proposed K01 application will address this gap by designing and evaluating a DMHI attuned to the unique needs and preferences of adolescents (14-17 years) who engage in NSSI. This project will leverage a moment of online information-seeking through MHA’s website, to deliver a low-intensity DMHI focused on acquisition and practice of evidence-based skills to improve self-regulation and deliver help-seeking information, to ultimately reduce NSSI frequency and encourage future treatment engagement. Partnering with MHA to deliver the DMHI provides a clear dissemination pathway and access to a diverse group of adolescents who are not in treatment. To design the DMHI, I will employ user-centered design activities, which involve key stakeholders in the research and design process to ensure adolescents’ needs and preferences are reflected in the final DMHI. I will also engage MHA stakeholders in the development of a strategic implementation and dissemination plan through their website. I will then pilot a randomized controlled trial (RCT) of the DMHI with 80 adolescents (14-17 years of age) randomized on a 1:1 basis to receive the DMHI (n=40) or an active psychoeducational control (n=40) for the duration of 8 weeks. This K01 will be a critical first step in positioning me to achieve my career goal and become a leading independent researcher in digital mental health. My four training aims are designed to support this overarching goal by extending my expertise in: 1) UCD and summative methods including usability testing for DMHIs and support further development of expertise in 2) the conduct of clinical trials, 3) scalable implementation methodologies, and 4) treatment models for adolescent NSSI. Accomplishment of...