The Latest Pot Myth, Smacked Down By Science
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Those opposed to the legalization and regulation of marijuana for any purpose, including the plant’s therapeutic use when authorized by a physician, often allege that the adoption of such laws will result in a significant increase in pot use by young people.
“The damage of marijuana—and these laws—is clear,” claims David Evans, executive director of the Drug Free Schools Coalition, in a recent open letter to US Attorney General Eric Holder and DEA Administrator Michele Leonhart. “Legalization of marijuana for ‘medical’ use and recreational use in those states has resulted in more marijuana use, particularly among young people.”
Adds Kevin Sabet, co-founder of Project SAM and a former senior policy advisor at the White House Office of National Drug Control Policy (aka the Drug Czar’s office), “Research shows that residents of states with medical marijuana laws have abuse and dependence rates almost twice as high as states with no such laws, and teen use rates are significantly higher in states with medical marijuana laws compared to other states. Moreover, youth perception rates of the harmful effects of marijuana have significantly decreased in states that have legalized medical marijuana.”
Sounds scary, doesn’t it? It's supposed to. But here’s the reality check: virtually every study to evaluate the potential impact of these laws on teen use rates proves these claims to be woefully false.
The most recent peer-reviewed smackdown of this stock prohibitionist claim appears online this month in the Journal of Adolescent Health. Researchers at Rhode Island Hospital and Brown University assessed the impact of medical cannabis laws over a 20-year period by examining trends in self-reported drug use by high schoolers in a cohort of states before and after legalization. Investigators compared these trends to geographically matched states that had not adopted medical marijuana access laws during this time.
Here’s what they found. “[O]ur study of self-reported marijuana use by adolescents in states with a medical marijuana policy compared with a sample of geographically similar states without a policy does not demonstrate increases in marijuana use among high school students that may be attributed to the policies.” In fact, researchers determined that in some regions of the country, the adoption of medical cannabis laws was associated with decreased cannabis use by young people, a finding that led the authors to acknowledge, “[C]oncerns about ‘sending the wrong message’ may have been overblown.”
They concluded, “Our study suggests that… the legalization of marijuana for medicinal purposes has not increased adolescent marijuana use, a finding supported by a growing body of literature.”
And what a growing body of literature it is. Here’s an overview of other, previous studies dismissing the notion that medical pot laws are a catalyst for increased drug use by either teens or adults.
Writing in 2013 in the American Journal of Public Health, researchers at the University of Florida College of Medicine evaluated the effects of medical marijuana laws on adolescent pot use rates for the years between 2003 and 2011. Investigators reported that the adoption of liberalized cannabis laws had no “statistically significant … effect on the prevalence of either lifetime or 30-day marijuana use” by adolescents residing in medical cannabis-friendly states. They concluded, “Our results suggest that, in the states assessed here, MMLs [medical marijuana laws] have not measurably affected adolescent marijuana use.”
A 2012 analysis of statewide cannabis laws and adolescent use patterns commissioned by the Institute for the Study of Labor in Germany drew similar conclusions. Economists from Montana State University, the University of Oregon, and the University of Colorado at Denver examined the relationship between the passage of medical cannabis laws and rates of marijuana consumption by high school students. Authors analyzed state and national data from the Center for Disease Control’s Youth Risky Behavior Surveys for the years 1993 through 2009, during which time more than a dozen states enacted law allowing for the production and use of cannabis for medicinal purposes. Authors determined, “[T]he legalization of medical marijuana was not accompanied by increases in the use of marijuana or other substances such as alcohol and cocaine among high school students. Interestingly, several of our estimates suggest that marijuana use actually declined with the passage of medical marijuana laws.”
A separate 2012 study by researchers at McGill University in Montreal and published in the journal Annals of Epidemiology reported virtually the same conclusions. Investigators obtained state-level estimates of marijuana use from the US National Survey on Drug Use and Health for the years between 2002 and 2009. Investigators utilized difference-in-differences regression models to estimate the causal effect of medical cannabis laws on marijuana use, and simulations to account for measurement error. "Difference-in-differences estimates suggested that passing MMLs (medical marijuana laws) decreased past-month use among adolescents ... and had no discernible effect on the perceived riskiness of monthly use,” authors reported. “[These] estimates suggest that reported adolescent marijuana use may actually decrease following the passing of medical marijuana laws."
Finally, a 2007 study conducted by a pair of researchers at the Texas A&M Health Science Center, Department of Epidemiology & Biostatistics also evaluated whether liberalizing medical cannabis use might stimulate broader experimentation among the general population. “Using the Arrestee Drug Abuse Monitoring system, data from adult arrestees for the period 1995-2002 were examined in three cities in California (Los Angeles, San Diego, San Jose), one city in Colorado (Denver), and one city in Oregon (Portland). Data were also analyzed for juvenile arrestees in two of the California cities and Portland. Data on emergency department patients from the Drug Abuse Warning Network for the period 1994-2002 were examined in three metropolitan areas in California (Los Angeles, San Diego, San Francisco), one in Colorado (Denver), and one in Washington State (Seattle).” After crunching the data, researchers reported, “[C]onsistent with other studies of the liberalization of cannabis laws, medical cannabis laws do not appear to increase use of the drug.”
So, will the publication of this latest study put to rest the false notion that medical cannabis legalization stimulates non-medical pot use? Probably not, but it is a start. Notably, government officials seem finally to be getting the message. Speaking to the Tampa Bay Times last month, the deputy director of the US National Institute on Drug Abuse acknowledged, "We cannot draw a clean link between medical marijuana and shifting drug usage rates.”