What happens to marijuana use when states legalize it

Green on the ballot. (Reuters/Robert Galbraith)
Green on the ballot. (Reuters/Robert Galbraith)
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The debate over marijuana regulation has been picking up steam, and 2016 may be a landmark year for marijuana legalization in the United States. In November, five states–Arizona, California, Maine, Massachusetts, and Nevada–will consider measures to legalize marijuana for recreational purposes on their ballots. Four other states–Arkansas, Florida, Montana, and North Dakota–are set to vote on medical marijuana initiatives.

The support for marijuana legalization has been steadily growing in recent years and an April 2015 survey by Pew Research found that 53% of Americans think that the drug should be made legal. The dramatic growth in the industry has been likened to a gold rush, with legal marijuana sales in 2015 reaching $5.4 billion.

Opponents of measures to legalize marijuana have long argued that such legislation would cause marijuana use to spike. A recent study carried out by the Cato Institute, a libertarian think-tank, looked at the impact of marijuana legalization in Colorado, Washington, Alaska and Oregon, for clues on how the policy plays out. Colorado and Washington legalized recreational use in 2012 while Alaska and Oregon did in 2014.

Using data from the National Survey on Drug Use and Health Results for Colorado, Washington and Oregon, the study examined changes in rates of marijuana consumption per month. The rate of increase in marijuana use didn’t change significantly after legalization in Colorado, Washington and Oregon. Marijuana use has been steadily increasing in all three states since the early 2000s.

Opponents of marijuana legalization are especially concerned that young people would use more marijuana if it’s legalized.  The study looked at surveys of health behaviors conducted in middle schools and high schools as part of the Youth Risk Behavior Survey in Colorado and Alaska, and found that there was no significant change in trends of youth marijuana use post-legalization. The data was not available for Washington and Oregon.

It could be that marijuana legalization occurs as marijuana use increases.  “All those observed patterns in marijuana use might provide evidence for a cultural explanation behind legalization: As marijuana becomes more commonplace and less stigmatized, residents and legislators become less opposed to legalization,” the authors wrote. “In essence, rising marijuana use may not be a consequence of legalization, but a cause of it.”

The authors of the study are Angela Dills, professor of regional economic development at Western Carolina University, Sietse Goffard, a researcher at the economics department at Harvard University and Jeffrey Miron, director of undergraduate studies in the economics department at Harvard University.