Al-Muhandis and Hunter focused on the role of community education interventions [45]. They included 22 studies and reported a pooled relative effectiveness of 0.25 (95%CI 0.17–0.37). The authors reported substantial heterogeneity but no significant publication bias, and investigated causes of heterogeneity using multi-level modelling. They found that 61% of heterogeneity could be explained by two variables (whether contemporary or historic controls were used and the time from intervention to assessment). Studies using historic controls substantially over-estimated intervention effectiveness compared to studies using concurrent control groups. When restricted to those studies with contemporary controls, educational interventions still appeared to be effective, but effectiveness declined after 18 months. There was no additional value of combining educational with chemical or biological interventions. GRADE suggested very low quality evidence.