Abstract: A total of 70 studies (44,958 participants) were included in the review, and 63 studies (42,784 participants) in the meta-analyses. Overall, the risk of bias assessment showed that these studies provided moderate or low quality evidence. Outcomes at four or more months post-intervention were of particular interest to assess when effects were sustained beyond the immediate short term. We have reported pooled effects across delivery modes only for those analyses for which heterogeneity across delivery modes is not substantial (I2 < 50%). Alcohol-related problems at four or more months: IFF standardised mean difference (SMD) -0.14, 95% confidence interval (CI) -0.24 to -0.04 (participants = 2327; studies = 11; moderate quality evidence), equivalent to a decrease of 1.28 points in the 69-point alcohol problems scale score. No effects were found for WF or MF. Binge drinking at four or more months: results pooled across delivery modes: SMD -0.06, 95% CI -0.11 to -0.02 (participants = 11,292; studies = 16; moderate quality evidence), equivalent to 2.7% fewer binge drinkers if 30-day prevalence is 43.9%. Drinking quantity at four or more months: results pooled across delivery modes: SMD -0.08, 95% CI -0.12 to -0.04 (participants = 21,169; studies = 32; moderate quality evidence), equivalent to a reduction of 0.9 drinks consumed each week, from a baseline of 13.7 drinks per week. Drinking frequency at four or more months: WF SMD -0.11, 95% CI -0.17 to -0.04 (participants = 9929; studies = 10; moderate quality evidence), equivalent to a decrease of 0.17 drinking days/wk, from a baseline of 2.74 days/wk; IFF SMD -0.21, 95% CI -0.31 to -0.10 (participants = 1464; studies = 8; moderate quality evidence), equivalent to a decrease of 0.32 drinking days/wk, from a baseline of 2.74 days/wk. No effects were found for GFF or MC. Estimated blood alcohol concentration (BAC) at four or more months: peak BAC results pooled across delivery modes: SMD -0.08, 95% CI -0.17 to 0.00 (participants = 7198; studies = 11; low quality evidence), equivalent to a reduction in peak BAC from an average of 0.144% to 0.135%. No effects were found for typical BAC with IFF. The results of this review indicate that no substantive meaningful benefits are associated with social norms interventions for prevention of alcohol misuse among college/university students. Although some significant effects were found, we interpret the effect sizes as too small, given the measurement scales used in the studies included in this review, to be of relevance for policy or practice. Moreover, the significant effects are not consistent for all misuse measures, heterogeneity was a problem in some analyses and bias cannot be discounted as a potential cause of these findings.

Plain-language summary: 70 studies were included in this review, with 44,958 students overall. We were interested mainly in studies with a follow-up period of four or more months to assess whether any effects were sustained beyond the immediate short term. In 43 of the trials, the social norms intervention was targeted at higher-risk students. 55 trials were conducted in the USA, with others form Australia, Brazil, New Zealand, Sweden and the United Kingdom. Delivery of social norms information included mailed feedback, web/computer feedback, individual face-to-face feedback, group face-to-face feedback and general social norms marketing campaigns across college campuses. Over the longer-term, after four or more months of follow-up, there was only a small effect of social norms information on binge drinking, drinking quantity, and peak BAC. For these outcomes, effects were not any different across the different delivery modes.Only small effects were found for web feedback and individual face-to-face feedback on frequency of alcohol consumed. Only a small effect of individual face-to-face feedback on alcohol related problems, but no effects were found for mailed or web feedback. Similarly, no effects were found for group face-to-face feedback or for marketing campaigns on frequency of alcohol consumed and typical BAC. Our reading of these results is that, although we found some significant effects of social norms information, the strength of the effects over the longer-term is very small and therefore this information is unlikely to provide any advantage in practice. Overall, only low or moderate quality evidence was noted for the effects reported in this review. Problems with study quality could result in estimates of social norms effects that are too high, so we cannot rule out the chance that the effects observed in this review may be overstated. The U.S. National Institutes of Health provided funding for just under half (33/70) of the studies included in this review. Eighteen studies provided no information about funding, and only 13 papers had a clear conflict of interest statement.