This report presents findings from a mixed methods systematic review of the Communities That Care (CTC) prevention system, which is designed to reduce youth problem behaviours by empowering local stakeholders to implement evidence-based interventions. By synthesising evidence from experimental, quasi-experimental designs and process evaluations, this report contains robust, policy-relevant insights into the conditions under which CTC is most effective.

Methods include a multi-level meta-analysis (MLMA) of impact studies and a narrative review of associated implementation papers. The meta-analysis systematically assessed the effectiveness of CTC on reducing youth violence and offending behaviour, drawing on data from 13 studies and 41 effect sizes, and explored potential moderators that may explain variation in outcomes across studies. The meta-analyses found an overall seven percent reduction in risk of youth violence and offending behaviour for areas using the CTC interventions versus those that did not. This positive finding is substantial but not statistically significant. Given the small number of studies and resulting lack of statistical power to detect small differences, the level of certainty of this finding is low. 

There was no strong evidence to suggest that there were differences in effectiveness based on location (country) or presence of violent behaviour, though there was weak evidence suggesting that decreases in violent behaviour were larger than decreases in offending behaviour. The narrative review of implementation papers found several barriers and facilitators related to implementation success, as well as some key strategies that may lead to better uptake and fidelity. For an area to effectively implement CTC, key factors include the community’s adoption of a science-based approach to prevention, selecting areas that have a culture and history of evidence-based program use and of evaluation, as well as the foundations for an active coalition in the form of community capacity and partnerships.