The effects of Positive Youth Development interventions on substance use, violence and inequalities : systematic review of theories of change, processes and outcomes

Background Positive Youth Development (PYD) delivered outside school aims to enable young people to develop positive assets such as relationships and confidence, rather than to merely address risk. Existing reviews of PYD effects on substance use or violence are old and unsystematic. Objectives To systematically review evidence to answer the following questions: what theories of change inform PYD interventions addressing substance use and violence? What characteristics of participants and contexts are identified as barriers to and facilitators of implementation and receipt in process evaluations of PYD? What is the effectiveness and cost-effectiveness of PYD in reducing substance use and violence? What characteristics of participants and contexts appear to moderate, or are necessary and sufficient for, PYD effectiveness? Data sources A total of 21 bibliographic databases; 35 websites and contacting authors. Review methods We included reports published in English since 1985 and reporting on theories of change, as well as process, outcome and economic evaluations of PYD targeting 11- to 18-year-olds and addressing substance use or violence. References were screened on title/abstract and, where appropriate, on full report. Data extraction and quality assessment used Critical Appraisal Skills Programme, Evidence for Policy and Practice Information and Co-ordinating Centre and Cochrane tools. Theories of change and process evaluations were qualitatively metasynthesised. Outcome evaluations were synthesised narratively and meta-analytically. Results 32,394 unique references were identified and 48 were included. A total of 16 reports described theories, 13 (10 studies) evaluated processes and 25 (10 studies) evaluated outcomes