PROJECT SUMMARY Youth involved in the legal system (YILS) have extremely high rates of substance and opioid use disorders (SUD/OUD) and do not have access to the resources to prevent serious use sequelae. SUD prevention and overdose prevention (harm reduction) interventions are critically important to delay escalation to synthetic opioids and prevent fatalities and health/legal consequences. Washington State is facing an overdose crisis; overdose deaths increased by 40% in a year, a steeper increase than any other state. Rural counties in this state report overdose rates that are as high or higher than urban ones. Thus, rural YILS are particularly vulnerable to overdose and lack adequate prevention services. Optimal SUD/OUD and overdose prevention for rural YILS requires a multifaceted approach, which our experienced team is ideally poised to develop, implement, and test. We have developed a successful hybrid remote-in person model in a previous grant working with the state juvenile incarceration system that is ideally suited to serving rural county court-involved YILS. We have strong support for this collaborative application from rural county court systems, who are motivated to intervene with YILS earlier in the spectrum of legal system and substance use involvement. Overall, the goal of the 2-year R61 phase will be to codesign a multilevel SUD/overdose strategy to prevent escalation to OUD/overdose among YILS in rural county juvenile court systems, and the tools needed to reliably implement this strategy. Specifically, we will collaboratively codesign components of a multilevel SUD/overdose prevention strategy with a multisector group representing state and local governments, service sector leaders, and consumer parents/YILS (R61 Aim 1). We will also codesign a reproducible implementation plan for the multilevel intervention developed in Aim 1 that can be reliably implemented in rural courts (R61 Aim 2). The overall goal of the 3-year R33 phase will be to test our codesigned strategy on implementation and effectiveness outcomes. We will do this by conducting a hybrid type 2 stepped wedge trial with 15 counties, surveying 470 youth (for an anticipated 360 complete cases) and tracking county implementation metrics every three months to understand effects of multilevel intervention including prevention education and harm reduction to reduce the harms attributable to active drug use. Outcomes will include implementation (reach and adoption; R33 Aim 1) and effectiveness (overdose and naloxone knowledge; frequency of use of overdose-associated and other substances; R33 Aim 2). This proposal is innovative, high impact, and highly responsive to RFA-24-036. With our substance use prevention experience and existing relationships with juvenile legal systems, we are uniquely positioned to be successful in engaging diverse perspectives with rural legal systems to codesign and test a multilevel substance and overdose prevention trial. The intervention and i...