A novel approach to assess descriptive and injunctive norms for college student marijuana use

Descriptive and injunctive norms are traditionally assessed using different metrics. Following an innovation in the alcohol field, we examined a novel measure of perceived descriptive and injunctive marijuana norms (i.e., Marijuana Norms Grid, MNG) to characterize how these normative perceptions relate to one's own use of marijuana. The present study addressed three research questions: (1) Do college students overestimate descriptive/injunctive marijuana norms of typical college students and close friends? (2) Are descriptive/injunctive norms uniquely related to marijuana frequency and quantity? (3) Are injunctive norms related to marijuana frequency and quantity above and beyond how injunctive norms are traditionally assessed? College students (n = 7000) were recruited from 9 universities throughout the US, including 2077 past month marijuana users. Participants completed an online, cross-sectional survey that included measures assessing marijuana use, marijuana consequences, and descriptive and injunctive marijuana norms using traditional and novel assessments, among other assessments. The results revealed robust self-other discrepancies using the MNG such that participants overestimated how often and how much college students use marijuana. We also found that both descriptive and injunctive norms related uniquely to one's own marijuana use. The MNG injunctive norms explained about 19% of additional variability in marijuana outcomes beyond injunctive norms assessed using the traditional method. The findings of the present study support the utility of the novel assessment of injunctive marijuana norms. Implications for norms-based interventions are discussed.