Efficacy of Social Norm Interventions on Addictive Behaviours—A Systematic Review and Meta-Analysis of Randomised Controlled Trials

Mental health-related behaviours including addictive behaviours contribute significantly to the global burden of disease. Social norm interventions appear to be a cost-effective means of reducing addictive behaviour. We conducted a systematic review and meta-analysis of the efficacy of social norm interventions for addictive behaviours. We searched the databases Medline and PsycInfo from inception to April 2024 as well as reference lists of eligible studies and related systematic reviews for randomised controlled trials (RCTs) comparing the efficacy of social norm interventions for addictive behaviours to control conditions. Out of the 11,515 potentially eligible RCTs, 52 trials with a total of 31,764 adult participants met inclusion criteria, with 45 trials targeting alcohol consumption, three trials targeting Marijuana use, two trials targeting other substance abuse and two trials targeting gambling. Overall, 37 trials were included in the random-effects meta-analysis. The comparison of social norm interventions to control conditions at posttreatment showed a small but statistically significant effect (g = −0.12; 95% CI = −0.22 to −0.02; p < 0.01). Risk of bias was rated low in 37 RCTs, 14 RCTs were rated as having some risk of bias concerns and one RCT was rated as having high risk of bias. Social norm interventions can be an effective intervention method for reducing substance abuse and gambling. Yet, data is largely derived from studies targeting alcohol consumption and current trials suffer from methodological and practical limitations. The small effect sizes need to be appraised in the context of cost-effectiveness of these interventions.