Improving student mental health through a universal trauma-informed intervention: Testing effectiveness and implementation of RAP Club - ABSTRACT. The COVID-19 pandemic exacerbated adolescent mental health problems and worsened disparities in their prevalence. While universal evidence-based school mental health programs are an effective way to reduce and prevent youth mental health issues, few such programs are, in fact, used in schools. Translation of research into practice averages 17 years, and most evidence-based programs are never sustainably adopted in real-world settings due to implementation barriers. RAP (Relax, Aware, Personal rating) Club is an evidence-based intervention to improve mental health among 8th grade students. Due to its trauma- informed approach and combination of mindfulness and cognitive behavioral skills, RAP Club is appropriate for 8th graders who have been exposed to chronic stress and trauma. Our team’s randomized control trial (RCT) in 29 urban public schools showed that, compared with an active control condition, RAP Club reduced symptoms of post-traumatic stress (PTSD), depression, and anxiety, as well as behavior problems, during the transition into high school. In the RCT, RAP Club sessions were delivered by research staff, which is not a sustainable or scalable delivery model. Thus, the objective of this type II hybrid effectiveness-implementation study is to test RAP Club’s delivery by school personnel, using a randomized factorial experiment to identify the most effective implementation approaches. We will examine the performance of two factors: (1) facilitator expertise (school personnel with versus without mental health expertise) and (2) supervision level (standard versus enhanced). Using a 2x2 factorial design, we will test four conditions that represent all combinations of these two factors. This design will allow us to identify the conditions that improve student mental health, strategically balanced by data on their implementation constraints (e.g., cost). We will test the impact of each of these four conditions on student PTSD symptoms (primary outcome) and anxiety symptoms, depressive symptoms, and behavior problems (secondary outcomes) at post-test and 4- and 12-month follow-ups (Aim 1: Effectiveness outcomes). For each of the four conditions, we will also evaluate cost, cost-effectiveness, and fidelity of implementation, as well as feasibility and acceptability (Aim 2: Implementation outcomes). Potential moderators of the effectiveness and implementation outcomes will be explored for each of the four conditions, including characteristics of schools (size, % low-income students), students (sex, trauma exposure), and facilitators (sex, years in profession) (Exploratory Aim 3: Potential Moderators). Findings will be used to create a toolkit that presents effectiveness and implementation data for each of the four conditions to guide education leaders in selecting strategies that maximize their current resources. Use of a factorial design to test program implementation strategies offers a novel and efficient model for streamlining translation of research into school- based practice. Findings will advance the science on school mental health interventions and will boost RAP Club’s potential for widespread adoption.