Development and evaluation of the efficacy of a web-based ‘social norms’-intervention for the prevention and reduction of substance use in a cluster-controlled trial conducted at eight German universities

BACKGROUND Previous research suggests that perceptions of peer substance use are associated with personal use. Specifically, overestimating use in the peer group is predictive of higher rates of personal substance use. 'Social norms'-interventions are based on the premise that changing these misperceived social norms regarding substance use by providing feedback on actual norms is associated with a reduction in personal substance use. Studies conducted in the U.S.A. suggest that 'social norms'-feedback is an effective strategy for reducing substance use among university students. It is unknown whether the effects of a 'social norms'-feedback on substance use can be replicated in a sample of German university students. The objective of this article is to describe the study design and aims of the 'INternet-based Social norms-Intervention for the prevention of substance use among Students' (INSIST)-study, a cluster-controlled trial examining the effects of a web-based 'social norms'- intervention in students enrolled at four intervention universities with those enrolled at four delayed intervention control universities. The INSIST-study is funded by the German Federal Ministry of Health. METHODS/DESIGN Eight universities in four regions in Germany will take part in the study, four serving as intervention and four as delayed intervention control universities (randomly selected within a geographic region). Six hundred students will be recruited at each university and will be asked to complete a web-based survey assessing personal and perceived substance use/attitudes towards substance use at baseline. These data will be used to develop the web-based 'social norms'-feedback tailored to gender and university. Three months after the baseline survey, students at intervention universities will receive the intervention. Two months after the launch of the intervention, students of all eight universities will be asked to complete the follow-up questionnaires to assess changes in perceptions of/attitudes toward peer substance use and rates of personal substance use. DISCUSSION This study is the first German cluster-controlled trial investigating the influence of a web-based 'social norms'-intervention on perceptions of/attitudes towards substance use and substance use behavior in a large university student sample. This study will provide new information on the efficacy of this intervention strategy in the German university context. TRIAL REGISTRATION DRKS00007635 at the 'German Clinical Trials Register' (17.12.2014).