Co-Designing Youth Mental Health Interventions: A Systematic Review of Practices and Outcomes.

This systematic review examined two questions regarding youth mental health intervention research: (1) how is co-design practiced? (2) what clinical and implementation-related outcomes are reported? Eligible studies were primary research published from 2008 involving youth aged 15-24 years co-designing mental health interventions. Studies were excluded if they were descriptive only, focused on prevention/screening, involved only adult perspectives, or were grey literature, conference proceedings, dissertations, or protocols. We searched seven databases (Medline, PsycINFO, CINAHL, Scopus, Global Health, EMBASE, Cochrane) using terms mapped to youth, co-design, mental health, and interventions, and conducted a narrative synthesis. Study quality was independently assessed by two reviewers with discrepancies resolved through consultation. Fifty-eight studies were included, predominantly from high-income, English-speaking settings, with a majority of qualitative (57%) and mixed-methods (36%) designs. Co-design typically involved small-group workshops with youth in consultative roles focused on adapting content or design. Over half of the studies did not report an explicit theoretical framework, and few examined relational dynamics within co-design. Only 12 studies evaluated mental health outcomes, with most reporting moderate-to-large improvements. Implementation outcomes were reported in 38% of studies, with generally high usability, engagement and improved alignment with user needs. Co-design evidence remains limited by inconsistent reporting and lack of rigorous outcome evaluation.