1. Nelson, Roxanne


Conflicting data and study methods make it hard to reach a firm conclusion.


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Marijuana is the most ubiquitous illicit drug in the country. More than half of all American adults have reported trying it at least once in their lives, and according to a recent Yahoo News/Marist poll, 14% of adults use it regularly-nearly as many as currently smoke cigarettes. Although marijuana is still an illegal drug under federal law, more than half the states have decriminalized its use in some form: currently, 29 states and the District of Columbia have legalized marijuana for medical or recreational use, or both. While the relaxation of state laws has undoubtedly affected access to the drug, it is not yet clear if marijuana legalization has affected usage among teens-particularly in states that allow its use for recreational purposes.

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Marijuana use is historically common among adolescents, and the drug has typically been easy to come by regardless of its legal status. Several studies have attempted to gauge its use among teens, but there have been contradictions in the findings as well as potential issues with the methodology.


A recent study found that adolescents residing in states with liberal marijuana laws (medical and/or recreational) were more than twice as likely to try alternative means of use-vaping and edibles-than those living in states with stricter laws. The study's lead author, Jacob T. Borodovsky of the Center for Technology and Behavioral Health at the Geisel School of Medicine at Dartmouth College, explains that this finding reinforces the idea that if marijuana is more available, teens are more likely to try it.


But Borodovsky notes that one of the problems associated with studying the effects of marijuana legalization is that laws and oversight differ by state. "New Hampshire has four medical marijuana dispensaries and one of the most restrictive medical marijuana laws in the country," he says, "while California has much looser oversight. So putting New Hampshire and California in the same analysis doesn't make sense. We have to sort this out if we want to figure out how legal dispensaries affect usage."


However, other studies have found that marijuana use among teens has not increased despite changing laws. Findings from the National Institute on Drug Abuse's annual Monitoring the Future survey, which measures drug use and related attitudes among eighth, 10th, and 12th graders, showed that past-year marijuana use is at its lowest level in over 20 years among eighth and 10th graders, and that between 2015 and 2016, the percentage of eighth and 10th graders using marijuana daily dropped from 1.1% to 0.7% and from 3% to 2.5%, respectively. Marijuana use by 12th graders remained the same, however, with 6% reporting daily use.


The survey did show, however, that past-year usage is somewhat higher in 12th graders living in states that have legalized medical marijuana (38.3%) compared with those that haven't (33.3%)-although previous research suggests these differences existed before the passage of medical marijuana laws.


Colorado and Washington. Several studies have analyzed data from Colorado and Washington, which in 2012 became the first two states to permit recreational marijuana use. The results are somewhat inconsistent, although none show a significant jump in teen use. State-level data from the National Survey on Drug Use and Health, sponsored by the Substance Abuse and Mental Health Services Administration, found that past-year marijuana use in both Colorado and Washington decreased among adolescents between the ages of 12 and 17. In Colorado, it declined from 20.8% in 2013-2014 to 18.4% in 2014-2015; in Washington, usage dropped slightly from 17.5% to 15.6% during the same period.


The 2016 Washington State Healthy Youth Survey, which included more than 230,000 students from all counties, reported that despite legalization of marijuana, usage among teens has remained steady. Six percent of eighth graders, 17% of 10th graders, and 26% of 12th graders stated they had used marijuana in the past 30 days, similar to what was reported in the 2014 youth survey. Overall, the use of marijuana among Washington teens has remained stable over the past 10 years.


Evidence exists, however, that fewer teenagers think of marijuana as a risky drug. The Monitoring the Future survey found that 31.1% of 12th graders perceived marijuana as harmful in 2016 compared with 58.3% in 2000. The 2016 Washington State Healthy Youth Survey also found a changing perception in some age groups regarding the risks of marijuana use. It reported that 48% of eighth graders felt that regular marijuana use could be risky, a decrease from the 53% reported in 2014.


A study by Cerda and colleagues in JAMA Pediatrics also found that the perceived harm of marijuana has decreased among Washington's eighth and 10th graders. But the researchers, who analyzed data from the 2010 to 2015 Monitoring the Future surveys, also found that marijuana use among Washington's eighth and 10th graders increased by 2% and 4.1%, respectively, between 2010-2012 (prior to recreational marijuana legalization) and 2013-2015 (after legalization). In Colorado, usage during the same time period had not changed despite legalization.


According to the study's lead author Magdalena Cerda, DrPH, MPH, an associate professor in the Department of Emergency Medicine at the University of California, Davis, "Across the country, use went down, which suggests that had there been no legalization in Washington, use would have been expected to decrease, rather than remain stable." She points out that their study compared Washington with other states that did not legalize marijuana, while the Washington State Healthy Youth Survey only looked at Washington. "The estimates we provided are not raw prevalence estimates for Washington and Colorado," she says, "but regression-adjusted estimates that control [for] the demographic and school characteristics of the individuals in those two states [so they are] statistically similar to the individuals in the whole country." Therefore, she adds, "we might not expect our estimates to be the same as the unadjusted prevalence numbers found when looking just at Washington."



Despite the lack of evidence of dramatic increases in teen marijuana use following legalization, it is still important to monitor how changes in the drug's legal status affect adolescents and how tailored interventions can effectively address their needs, says Denise Walker, PhD, director of the Innovative Programs Research Group at the University of Washington School of Social Work in Seattle. "I believe strongly that legalization could have a number of inadvertent impacts, including [changes in] how adults perceive and provide messages to kids regarding use," she says. For example, the frequency of referral for evaluation or treatment of cannabis use disorders might change if fewer adults perceive the drug's overuse as cause for concern. Or, school administrations might not enforce policies regarding marijuana possession-and intoxication-sending the message to teens that using it is inconsequential or harmless.


In fact, several studies have identified cognitive changes over time in young marijuana users. In a recent prospective study of 294 boys tested annually from ages 10 through 17 and again at age 20, an earlier age of onset and more frequent use of marijuana were associated with declines in verbal IQ and some executive functioning tasks.


Walker emphasizes that health care providers need to continue assessing and discussing marijuana use with teens. "There are methods for talking about it that are more helpful, such as motivational interviewing techniques, rather than confrontation or scare tactics."


Borodovsky agrees, and suggests that in the clinical setting, it's helpful to broach the topic privately with teens and reassure them that the discussion will be confidential. He adds that teens may be more apt to disclose marijuana use if they're given the chance to answer questions about it on an electronic device while waiting to be seen.


"The DARE [Drug Abuse Resistance Education] approach does not work, and threats do not work-we've moved past that," he says. "But kids have to realize that just because marijuana may be legal and has medicinal value, it's not harmless."-Roxanne Nelson