College of Public Health and Human Sciences

Background

Oregon students' rates of marijuana use have increased following recreational marijuana legalization (RML), but the relation between RML and students' perceived peer use of marijuana - or descriptive norms - is unknown.

Objectives

This study examined whether perceived peer use of marijuana changed more following RML for college students in Oregon than in states without RML.

Methods

Repeated cross-sectional data were collected from the National College Health Assessment-II surveys from 2008 to 2016 to assess changes in descriptive norms ("Within the last 30 days, what percent of students at your school used marijuana?") among 18-26 year-old undergraduates from two Oregon institutions and 123 institutions in non-RML states (N = 280,006; 66.23% female; 33.19% male) following Oregon RML (7/1/2015). Mixed-effects regressions were used to account for clustering at the institutional level; models controlled for covariates and secular changes in descriptive norms.

Results

RML was associated with higher perceived rates of marijuana use by peers [Percent Increase = 3.09, p < .001]. The effect was significant for respondents who had never used marijuana [Percent Increase = 3.72, p < .001], but not for respondents who recently or ever previously used marijuana. Respondents who had recently used marijuana had higher descriptive norms than those who had never used [Percent Increase = 12.83, p < .001].

Conclusions

Given the association between descriptive norms and personal use, RML-related increases in descriptive norms among non-using students could contribute to future marijuana use initiation and may be one mechanism linking RML with higher rates of marijuana use among college students.