PROJECT 1 SUMMARY For youth receiving care in community mental health centers (CMHCs), comorbidities are the rule rather than the exception.1,2 Using measurement-based care (MBC) as the foundation of treatment for youth with comorbid problems significantly improves the therapeutic impact as it can help define the treatment focus. MBC is the systematic, routine evaluation of symptoms to inform care decisions. Especially in youth, MBC increases the rate of symptom improvement,3 detects clients who would otherwise deteriorate,4 and alerts clinicians to non- responders.4,5 Implementing MBC with fidelity requires 3 elements: (a) routine administration of measures for symptoms, outcomes, and processes before therapy sessions, (b) therapist and client score review, and (c) collaborative reevaluation of the treatment plan. But MBC is rarely implemented with fidelity; less than 15% of providers report using MBC per recommendations.6 Previous efforts to support MBC implementation have yielded suboptimal outcomes because CMHC leaders are challenged to identify and prioritize barriers and select strategies to overcome them. New methods are needed for identifying and prioritizing determinants, and matching strategies to determinants, to optimize MBC implementation and treatment quality to improve youth mental health outcomes in community settings. Project 1's optimization goals are to increase impact of MBC and align methods with preferences of practice partners. IMPACT Center methods will be piloted in six diverse CMHC clinics (three of six serve primarily Latinx populations). IMPACT methods we focus on include (a) rapid evidence reviews to uncover empirical data regarding MBC determinants; (b) rapid ethnography to identify and describe local determinants and situate them in specific organizational, social, and task contexts; and (c) design probes (e.g., kits with disposable camera, journals, maps) to allow practice partners and youth to capture and reflect on aspects of their context that are salient for MBC. These activities will result in a list of determinants that will be rated by partners from each clinic for criticality, chronicity, and ubiquity to generate priority scores. Subsequently, we will use facilitated group processes to develop causal pathway diagrams to match strategies to the top three determinants and clarify their preconditions, moderators, mechanisms, and proximal and outcomes (definitions in Methods Core) at each of the six clinics to yield a plan to optimize MBC implementation (Aim 1). We will check back with clinic-specific implementation teams to track strategy deployment for six months. We will then compare MBC treatment quality for another six months post implementation with data from two years of historical controls (Aim 2). Finally, we will co-design toolkits for each of the five IMPACT Methods for the practice and scientific communities (Aim 3). Results from Aims 1 & 2 will support an R01 testing practice partner-led efforts, u...