- College students in states with recreational marijuana laws are 18 percent more likely to have used cannabis within the past 30 days compared to students in states where it remains illegal.
- Across the country, rates of overall usage rates for marijuana had a modest increase of 3 percent growing from 14 to 17 percent.
- In states with legalized recreational marijuana there was a marked decline in rates of binge drinking.
College students in states with legalized recreational marijuana are more likely to smoke marijuana and smoke it more frequently than in states where the drug remains illegal.
But, they are less likely to binge drink.
The research is a substantial addition to prior literature on the subject, as much of it only looked at changes in drug use within the first year after legalization. This research included data for up to 7 years following legalization from seven states and 135 colleges from states where recreational marijuana is legal and 41 states and 454 colleges where it is not.
“Our study was motivated, in part, because there was a lack of studies examining the effects of [recreational marijuana legalization] on marijuana use and other substance use even after 7 years of passage of these laws,” Harold Bae, assistant professor of biostatistics, College of Public Health and Human Sciences, Oregon State University, and author of the research, told Healthline.
Perhaps unsurprisingly, marijuana use went up.
College students in states with recreational marijuana laws were 18 percent more likely to have used cannabis within the past 30 days compared to students in states where it remains illegal.
Frequent use, defined as using marijuana at least 20 of the past 30 days, was also more prevalent. Students were 17 percent more likely to have used frequently where the drug is legal.
Looking across the country, rates of overall usage rates for marijuana had a modest increase of 3 percent (growing from 14 to 17 percent). However, when compared to the earliest states to legalize marijuana, overall usage surged 13 percent, climbing from 21 to 34 percent.
Dr. Scott Krakower, assistant unit chief of psychiatry at Zucker Hillside Hospital in Glen Oaks, New York, said the results of the study were not surprising. Dr. Krakower wasn’t affiliated with the research.
“When you’re looking at rates of legalization it is sending messages to people that they can readily go in and obtain a substance,” he said.
But according to Bae and his colleagues, their research offers more insight into the effects of marijuana legalization than just demonstrating that liberalization of marijuana laws leads to more marijuana use — a point many might just consider common sense.
A notable finding from the research was that in states with legalized recreational marijuana there was a marked decline in rates of binge drinking, defined as drinking five or more alcoholic beverages in a single session within the last 30 days.
Over a 10-year period, in states with recreational marijuana, students were
While the study authors speculate somewhat on why this association appears, they say it is far too early to conclude that marijuana legalization leads to less binge drinking.
“We were not able to examine causation between these two patterns,” said Bae. “These two findings do not establish any temporal link or causation. More substantial longitudinal data is necessary to clarify the association.”
Other experts say that the data is in line with other research on the relationship between marijuana legalization and alcohol use.
“These findings are consistent with prior evidence indicating that in some populations cannabis appears to be a substitute for, rather than a compliment to, alcohol,” said Paul Armentano, the deputy director of NORML (National Organization for the Reform of Marijuana Laws).
“It is also notable that this study failed to identify any parallel uptick in young adults’ consumption of other controlled substances, once again refuting the allegation that cannabis is a supposed ‘gateway drug’ and reenforcing the concept that, for some people, it acts as an exit substance,” he added.
While the findings on the association between binge drinking and and marijuana legalization have garnered the lion’s share of publicity, Bae says that his work has more substantial, practical implications.
For example, rates of marijuana use differed based on groups. Increases in use were more pronounced among women, students age 21 years and older, and individuals who lived off campus.
A better understanding of individuals more likely to be affected by marijuana legalization could lead to more informed public health messaging and care for higher-risk groups.
“As an example, a college that ordinarily conducts marijuana use prevention programming only in the residence halls might, as a result of this study, devote additional resources to reach off-campus students who were found to be more sensitive to legalization,” said David Kerr, associate professor, School of Psychological Science, Oregon State University, and a co-author of the research.
Krakower agrees, noting that this kind of demographic data for marijuana use could help lead to better screening for individuals with certain common comorbidities with substance use such as anxiety and depression.
“If you can see that marijuana use is increasing among that age group then we would certainly look for that in terms of targeting more questions towards people of that age group about marijuana,” he said.