Recreational marijuana legalization (RML) went into effect in the state of Oregon in 2015. A recent study compared changes in rates of marijuana use among college students in Oregon before and after RML to rates of use among college students in states where RML did not occur. Data on self-reported past-month marijuana use and frequency of heavy alcohol use were collected from the Healthy Minds Survey (HMS). Participants in the experimental group were students at a public Oregon university who completed the HMS in 2014 (n = 588) and in 2016 (n = 1,115). Participants in the control group (n = 9,221) were students at six U.S. universities in states were recreational marijuana was illegal who completed the HMS in 2016 and at least once between 2012 and 2015. Average participation rates for the pre- and post-RML HMS were 31.2% and 26.3%, respectively. Results indicated overall past-month marijuana use rates increased from 21.7% to 23.8% (p = 0.03) throughout the study period, although use rates varied by campus, while rates of heavy drinking decreased (p = 0.005). Among Oregon students who reported recent heavy alcohol use, RML was associated with 73% greater odds of past-month marijuana use, adjusting for secular trends in use, correlation, and potential covariates. This relationship was not observed for Oregon students who did not report heavy alcohol use.
Take away: Past-month marijuana use rates significantly increased following the legalization of recreational marijuana among Oregon college students, but only among those who reported recent heavy alcohol use.