Marijuana use is is sharply rising in the United States, but the trend is not the result of the growing number of state laws that allow legal use of recreational or medical marijuana.
That’s the conclusion of a study in the journal Addiction that was published online this week.
“Medical and recreational marijuana policies did not have any significant association with increased marijuana use,” the study found. “Marijuana policy liberalization over the past 20 years has certainly been associated with increased marijuana use; however, policy changes appear to have occurred in response to changing attitudes within states and to have effects on attitudes and behaviors more generally in the U.S.”
Researchers at the Public Health Institute’s Alcohol Research Group analyzed data from periodic National Alcohol Surveys and stacked its results on marijuana use against changes in state laws.
Twenty-nine states and Washington, D.C. have comprehensive legal medical cannabis programs, and eight states and D.C. have legalized marijuana for adults over 21 years of age.
They found that instead of being caused by policy changes, the rise in cannabis use was “primarily explained by period effects,” meaning societal factors that affect populations across age and generational groups. The authors identify a decreasing disapproval of marijuana use as one such factor potentially at play.
But they are clear that the rise in use was not caused by changes to marijuana laws.
“The steep rise in marijuana use in the United States since 2005 occurred across the population and is attributable to general period effects not specifically linked to the liberalization of marijuana policies in some states,” the paper’s abstract says.
They authors also reasoned that respondents in earlier surveys taken pre-legalization may have been less likely to admit to marijuana use because of its criminalization. If true, and people are now more likely to admit to consumption under legalization, that would even further emphasize the point that ending prohibition doesn’t necessarily increase use; it just makes people more likely to fess up to it when a stranger calls on the phone with survey questions about the drug.
The new results come one week after the latest edition of an annual federal survey found that cannabis consumption by teens is at its lowest level since 1994 despite the fact that more states are changing their marijuana laws every year.
California was the first state to legalize medical cannabis in 1996.
“Marijuana use among adolescents aged 12 to 17 was lower in 2016 than in most years from 2009 to 2014,” that survey, the National Survey on Drug Use and Health, reported.
Colorado and Washington State became the first places to legalize recreational marijuana in 2012, with sales going into effect in 2014.
Together, the results of the two studies provide a counterpoint to legalization opponents’ claims that ending prohibition leads to skyrocketing use rates.