Oregon legalized medical marijuana in 1998, and in 2015 it legalized recreational use. In 2016, California followed suit, yet policymakers still know relatively little about the impact of recreational legalization.
by Oregon State University researchers and others shows that cannabis use has increased among college-aged Americans in states that legalized recreational use.
鈥淪ome people would be surprised that we didn鈥檛 already know this,鈥� said David Kerr, a psychology professor at Oregon State and the study鈥檚 lead researcher. 鈥淭here have been a number of studies that have found increases in adults, but not in young adults. So this is new and important information.鈥�
The researchers found that use among those in college only increased 1% after legalization, from 20% to 21%, while use among those not in college rose 5 percentage points, from 23% to 28%.
The study, published in the American Journal of Preventive Medicine, is based on 2008 to 2019 data from the National Survey on Drug Use and Health, which conducts an annual survey on drug and alcohol use across the country. The researchers looked at cannabis use for those 18 to 23 years old. They did not single out Oregon data or analyze the reasons behind the increased use.
Twenty-three states and the District of Columbia allow recreational marijuana use, with Colorado and Washington state the first to do so in 2012. A total of 38 states and the District of Columbia allow medical marijuana use, according to .
Previous studies have been mixed on the impact of legalization on young adults, Kerr said.
He speculated that the ready availability of marijuana and growing acceptance of its use could account for the increased use.
鈥淪ubstance use is very much influenced by what we think other people are doing,鈥� Kerr said.
on drug use showed that in 2020, about 20% of young adults believed regular cannabis use could be harmful compared with nearly 60% two decades ago.
With increased use, there has been a rise in frequent use, though not uniformly. The latest study found among non-college students a 2 percentage-point uptick in frequent use, from 12% to 14% after legalization. They defined frequent use as at least 20 times in the past month. Frequent use did not change among college students 鈥� it remained at 7%.
They found a similar trend when looking at addiction rates or cannabis use disorder, which they defined as users having difficulty stopping or having marijuana use control their lives. Cannabis use disorder stayed the same among college students 鈥� at 10%. But rates increased among non-college participants from 12% to 15%.
鈥淭hat might not be at the same level of addiction that we think about when we think about cigarettes or alcohol, but it is showing a pattern of problematic use,鈥� Kerr said. 鈥淚 think people should be concerned about that because that does mean someone is using it in a way that鈥檚 interfering with their ability to function the way that they would want to function, whether that be in school or home or work.鈥�
Kerr said because there are fewer social consequences to marijuana use now that the study might have underestimated the increases.
The study did not account for the fact that the potency of cannabis is higher in legal states, and has increased dramatically over time, nor did it not look at the effects of overconsumption of marijuana. But Kerr said the data is still useful for policy decisions on advertising, for example, limits on the ability of minors to access marijuana and the density of retail outlets in various communities.
As with any study, this one answered some questions while showing other avenues which need to be researched. Kerr said he鈥檇 like to explore the behavioral impact of cannabis. One question he has is whether increased use of marijuana leads to decreased consumption of alcohol.
鈥淲e need to understand how these policies are actually affecting behavior,鈥� Kerr said.
The research was funded by the National Institutes of Health. The other researchers included Natalie Levy, a Ph.D. student at Columbia University; Harold Bae, an associate professor at Oregon State; and Anne Boustead, assistant professor at Arizona State University.
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