The paper highlights the growing importance of involving service users and providers in designing and delivering health services to enhance quality of care. While providers offer valuable system-based insights, patients and families provide unique perspectives on service appropriateness. Studies show that involving these stakeholders improves service delivery, reduces hospital admissions, and advances care models and organizational processes. Co-design, a method that engages all stakeholders as equal partners, is increasingly used to improve healthcare. Community-based participatory research (CBPR) shares similar collaborative principles, actively engaging community members in all research phases. The authors emphasize the potential of CBPR and co-design to bridge the research-practice gap, particularly within youth opioid use treatment services, which often fail to consider the unique needs of youth and families. The ongoing opioid crisis in Canada, especially its impact on youth, underscores the urgency of improving access to and the quality of these services. Current treatment guidelines for youth with opioid use disorder (OUD) include pharmacological and psychosocial interventions, yet youth face numerous barriers, including age restrictions, provider hesitancy, and a lack of youth-friendly options. These barriers often result in lower engagement with treatment compared to adults. The paper aims to demonstrate how CBPR and co-design can be effectively integrated to address these challenges, focusing on two case studies from the Improving Treatment Together (ITT) project.

The paper reviews existing literature on patient and family engagement in healthcare, emphasizing the benefits of co-design and CBPR methodologies. It highlights studies demonstrating improvements in service delivery, reduced hospital admissions, and the development of family-oriented programs resulting from patient involvement. The review also underscores the importance of co-design's unique approach, which actively engages end-users as design partners rather than mere participants. The literature supports the use of CBPR to address health disparities among underserved populations. The authors note that although CBPR and co-design approaches are increasingly used, few studies demonstrate how to effectively integrate them and engage underserved populations in co-design, particularly within the context of youth opioid use treatment. This lack of methodological guidance makes the paper's contribution particularly significant.

The Improving Treatment Together (ITT) project combined CBPR and co-design methods to improve the experiences of youth, caregivers, and service providers in four BC communities. The study used a design thinking approach with six iterative steps: empathize, define, ideate, prototype, test, and implement. Phase 1, previously published, involved establishing partnerships with the Canadian Centre on Substance Use and Addiction (CCSA) and four Foundry centers. Youth team members with lived experience were trained and involved in recruiting participants (youth, caregivers, and service providers) for workshops. These workshops focused on understanding participants' experiences and needs (empathize) and developing problem statements (define). Participants then brainstormed ideas (ideate) and created low-fidelity prototypes (prototype). Phase 2, the focus of this paper, involved selecting three prototypes from Phase 1 for development and implementation. An internal decision-making framework assessed feasibility, affordability, sustainability, and scalability. Community champions (CCs) were hired to support local development with co-design teams. Phase 3 involved implementation and evaluation. The paper focuses on two case studies from Phase 2: the co-design of a caregiver handbook in Victoria and a virtual OAT guide in Kelowna and Vancouver. Both case studies detail the co-design process, including team composition, methods used (working groups, interviews, feedback grids), challenges encountered (COVID-19 pandemic, resource constraints, diverse sampling), and process evaluations using surveys adapted from the Public and Patient Engagement Evaluation Tool (PPEET).

**Case Study 1 (Caregiver Handbook):** A family peer supporter (CC) co-led the handbook development with an ITT project lead. A working group of 12 caregivers met regularly to develop content, illustrations, and design. Challenges included participant attrition due to various factors. The handbook underwent multiple revisions, including feedback from service providers and a provincial family advisory group. Process evaluation showed caregivers felt supported and satisfied with their involvement, believing the handbook would have a positive impact. Limitations included the mainly white, middle-class, female sample of caregivers. **Case Study 2 (Virtual OAT Guide):** Three CCs co-led the development with an ITT project lead and a youth team member. Ten youth actively receiving or having received OAT in the past five years participated. The process involved interviews with youth to identify key topics, followed by content drafting informed by clinical evidence and consultation with experts. Character personas were created through consultation with youth. An animated video series in a podcast format was created. A working group reviewed the content, structure, and design. Process evaluation indicated positive experiences and satisfaction among participants who felt supported, heard, and that the guide would have a positive impact. Limitations included difficulties connecting in person due to the pandemic and challenges engaging more youth due to the length of the process and COVID restrictions.

The case studies illustrate the successful integration of CBPR and co-design methods to improve healthcare experiences. CBPR helped establish strong community partnerships, supporting project activities across all phases. Co-design enabled creative engagement to understand stakeholders' needs and develop solutions. Community champions played a crucial role in recruiting participants, building trust, and navigating challenges, including those posed by the COVID-19 pandemic. The authors highlight the importance of establishing trusting relationships, considering power dynamics, and employing trauma-informed approaches when working with vulnerable populations. The flexibility in engagement strategies was vital to adapting to changing participant needs and project goals. Both innovations directly addressed needs expressed by youth and caregivers, aligning with existing research. The virtual OAT guide, in particular, addresses the issue of youth being dissuaded from accessing OAT.

This study successfully demonstrates the benefits of weaving CBPR and co-design methods to develop impactful innovations for underserved populations. The integration of these methods is crucial for establishing strong partnerships, facilitating engagement, and ensuring that solutions are accepted and endorsed by the target groups. While resource-intensive, this approach resulted in the creation of a caregiver handbook and a virtual OAT guide, both of which directly addressed identified needs. Future research should focus on evaluating the resources’ broader impact and exploring further strategies to mitigate the challenges posed by resource constraints and engagement of diverse participants.

The study acknowledges limitations inherent in CBPR and co-design processes, including their time and resource-intensive nature, particularly within resource-constrained settings and in the face of unexpected public health crises. Sampling bias, a common issue in co-design, may have resulted in limited representation of certain populations. The COVID-19 pandemic also presented significant challenges to the recruitment and engagement of participants. Furthermore, variations in feedback collection methods might have affected the consistency of data collected, particularly with regard to the caregiver handbook. While traditional iterative testing and redesign cycles were not fully realized due to time and resource constraints, the resources were created with the intention of reducing stigma and encouraging personal approaches to care, rather than providing one-size-fits-all solutions.