PUB - Publikationen an der Universität Bielefeld

## Background and research questions Licit and illicit substance use (i.e., using alcohol, tobacco, cannabis and other illicit drugs) is a key public health concern among university students in Europe. The delivery of normative feedback based upon the so called ‘social norms approach’ has shown promising results regarding substance use reduction. The approach stems from previous international research indicating that incorrect perceptions of high rates of peer substance use are predictive of an increased personal use. North-American ‘social norms’-intervention studies show that providing feedback on actual peer consumption rates to students leads to a reduction of social pres-sure on the individual and may consequently reduce personal substance use. To date, work on this issue has largely been restricted to the North-American college system and little is known about the peer influence on personal substance use in European, particularly in German students. Therefore, it remains unclear if social norms-interventions may be a viable method to reduce substance use in European students. The key research question of this thesis is: Are peers a relevant factor for personal substance use of European, particularly German students, and, do basic requirements for the implementation of social norms-interventions to reduce substance use exist in Europe? ## Methods Social learning theories were used to explain modifications in substance use behaviour among university students. In this regard, associations between internal and external locus of control and licit and illicit substance use were evaluated. As a basis principle of the social norms ap-proach, discrepancies between estimated peer and personal substance use behaviour were as-sessed, and associations between perceptions of peer and personal substance use among Euro-pean university students were examined. Data were collected in the context of a German multicentre cross-sectional study (Gesundheitssurvey NRW) and an EU-funded study conducted in seven European countries (Social Norms Intervention for the prevention of Polydrug usE (SNIPE)). ## Results The results of the German survey showed that licit and illicit substance use are not associated with high internal locus of control and that high social-external locus of control is associated with low illicit substance use. Considerable discrepancies were observed between personal licit and illicit substance use and perceived peer use among European students. The majority of students across all seven participating European countries thought that their peers use licit and illicit substances more frequently than themselves. In addition, higher perception of peer licit and illicit substance use was associated with higher odds for own substance use. For instance, the perception that the majority of peers had consumed illicit substances at least once in their lives was associated with an odds ratio of 1.97 (95% CI: 1.53-2.54) for own lifetime use of illicit substances. ## Conclusion Students perceive substance use of peers to be higher than their personal use. Given the association between perceptions of substance use and personal substance use, basic requirements for the implementation of social norms interventions in European student populations exist. These findings lead to the conclusion that interventions addressing perceived norms, already widely used in the North-American educational system, may be a viable method to change substance use among European students. To gain knowledge about the feasibility and efficacy of interventions based upon the social norms approach in European societies, prevention approaches which take the phenomenon of misperceived norms into consideration should be designed and tested.