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College students use more marijuana in states where it's legal, but binge drink less

By Molly Rosbach, Oregon State University, Thursday, March 19, 2020

Marijuana use among college students has been trending up for years, but in states that have legalized recreational marijuana, use has jumped even higher.

An Oregon State University study published in the medical periodical Addiction in January 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 percent 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 percent 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 percent more likely to have used marijuana than their peers in nonlegalized states.

The study, conducted by Harold Bae from OSU’s College of Public Health and Human Sciences and David Kerr from the College of Liberal Arts, is the first to look broadly at multiple states that have legalized recreational marijuana and to go beyond the first year following legalization.

It includes data from 135 colleges in seven states where marijuana was legalized by 2018 and from 41 states and 454 colleges where recreational use was not legal.

More than 850,000 students participated in the National College Health Assessment survey from 2008 to 2018, which provided the data. The survey asked about a wide range of health behaviors including drug and alcohol use and is administered anonymously.

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.

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, researchers found.

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.

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