Summary: Marijuana use rates are increasing in college students in states where recreational use has been legalized. Following cannabis legalization, binge drinking rates between the cohort group fell significantly.
Source: Oregon State University
Marijuana use among college students has been trending upward for years, but in states that have legalized recreational marijuana, use has jumped even higher.
An Oregon State University study published today in Addiction shows that in states where marijuana was legalized by 2018, both occasional and frequent use among college students has continued to rise beyond the first year of legalization, suggesting an ongoing trend rather than a brief period of experimentation.
Overall, students in states with legal marijuana were 18% more likely to have used marijuana in the past 30 days than students in states that had not legalized the drug. They were also 17% more likely to have engaged in frequent use, defined as using marijuana on at least 20 of the past 30 days.
The differences between states with and without legalization escalated over time: Six years after legalization in early-adopting states, students were 46% more likely to have used marijuana than their peers in non-legalized states.
Between 2012 and 2018, overall usage rates increased from 14% to 17% in non-legalized states, but shot up from 21% to 34% in the earliest states to legalize the drug. Similar trends appeared in states that legalized marijuana more recently.
Conducted by Harold Bae from OSU’s College of Public Health and Human Sciences and David Kerr from OSU’s College of Liberal Arts, this is the first study of college students to look broadly at multiple states that have legalized recreational marijuana and to go beyond the first year following legalization.
It includes data from seven states and 135 colleges where marijuana was legalized by 2018 and from 41 states and 454 colleges where recreational use was not legal.
That scope allowed Bae and Kerr to examine trends in the earliest adopting states as well as more recent adopters – though, the data for the study is stripped of state- and college-identifying information, so does not speak specifically to any one state or institution.
The data comes from the National College Health Assessment survey from 2008 to 2018, which asks about a wide range of health behaviors including drug and alcohol use and is administered anonymously to encourage students to respond more honestly. More than 850,000 students participated.
Looking at specific demographics, researchers found that the effect was stronger among older students ages 21-26 than minors ages 18-20; older students were 23% more likely to report having used marijuana than their peers in non-legalized states. The effect was also stronger among female students and among students living in off-campus housing, possibly because universities adhere to federal drug laws that still classify marijuana as an illegal substance.
“It’s easy to look at the findings and think, ‘Yeah, of course rates would increase,'” Kerr said. “But we need to quantify the effects these policy changes are having.”
Furthermore, he said, researchers are not finding increases in adolescents’ marijuana use following legalization. “So it is surprising and important that these young adults are sensitive to this law. And it’s not explained by legal age, because minors changed too.”
A recent companion study published in Addictive Behaviors in November by OSU doctoral candidate Zoe Alley along with Kerr and Bae examined the relationship between recreational marijuana legalization and college students’ use of other substances.
Using the same dataset, they found that after legalization, students ages 21 and older showed a greater drop in binge drinking than their peers in states where marijuana was not legal. Binge drinking was defined as having five or more drinks in a single sitting within the previous two weeks.
Researchers have not yet tested any hypotheses as to why binge drinking fell, but they have some ideas.
An outside study previously found that illegal marijuana use decreases sharply when people hit 21 – where there is a sharp increase in alcohol use.
“When you’re under 21, all substances are equally illegal,” Alley said.
“In most states, once you reach 21, a barrier that was in the way of using alcohol is gone, while it’s intact for marijuana use. But when marijuana is legal, this dynamic is changed.”
Binge drinking has been on the decline among college students in recent years, but dropped more in states that legalized marijuana than in states that did not.
“So in these two studies we saw changes after legalization that really differed by substance,” Kerr said. “For marijuana we saw state-specific increases that went beyond the nationwide increases, whereas binge drinking was the opposite: a greater decrease in the context of nationwide decreases.”
The magnitude of effect was much larger with marijuana than with any of the other substances, Bae added. “So the changes following recreational marijuana legalization were quite specific to cannabis use.”
Marijuana use trends among college students in states with and without legalization of recreational use: initial and longer‐term changes from 2008 to 2018
Background and aims Young adult college students in the United States are likely to be affected by marijuana liberalization trends. However, changes in students’ marijuana use following recreational marijuana legalization (RML) have not been examined in more than one RML state at a time, or beyond 1–2 years post‐legalization.
Design Cross‐sectional National College Health Assessment survey administered twice yearly from 2008 to 2018.
Setting A total of 587 4‐year colleges and universities in 48 US states.
Participants Undergraduates aged 18–26 years attending college in US states that did (n = 234 669 in seven states) or did not (n = 599 605 in 41 states) enact RML between 2008 and 2018. Measurements Self‐reported marijuana use (past 30 days) and individual and contextual covariates, institution‐provided institutional and community covariates and publicly available dates when states enacted RML.
Findings Adjusting for covariates, state differences and state‐specific linear time trends (accounting for pre‐RML trends), prevalence of 30‐day marijuana use increased more among students exposed to RML [odds ratio (OR) = 1.23, 95% confidence interval (CI) = 1.19–1.28, P < 0.001] than among non‐RML state students throughout the same time‐period; the results were similar for frequent use (≥ 20 days) (OR = 1.18, 95% CI = 1.10–1.27, P < 0.001). Interaction models supported stronger RML effects among students who were female, residing off‐campus and aged 21 years and older; sexual orientation did not moderate RML effects. In the earliest states to enact RML (2012) there were increases in use prevalence in the second through the sixth year post‐RML compared to pre‐RML. In the second legalization group (2015) there were increases in the first and second year post‐RML, and greater increases in the third year. In the later states (2016–17), increases were observed in both years after RML.
Conclusions In US states that enacted recreational marijuana legislation from 2012 to 2017 there was evidence for a general trend towards greater increases in marijuana use by college students and differential impact by gender, legal using age and campus residence.
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