WASHINGTON - A rise in marijuana use among U.S. teens over the past 20 years has no significant tie to the legalization of marijuana for medical use in many states, according to a new research paper.
Comparing surveys of marijuana use by adolescents conducted annually by the federal Centers for Disease Control and Prevention, researchers found the probability that a high schooler had used pot in the last 30 days was no more than 0.8 percent higher in legal states compared to states that had not approved medical marijuana.
"Our results are not consistent with the hypothesis that the legalization of medical marijuana caused an increase in the use of marijuana among high school students," D. Mark Anderson of Montana State University, Daniel Rees of the University of Colorado and Benjamin Hansen of the University of Oregon wrote.
Twenty-one states and the District of Columbia have legalized the use of marijuana for medical purposes, while two states, Colorado and Washington, now allow recreational use. Alaska and Oregon are set to vote on legalization for recreational use in November, while supporters of full legalization in the nation's capital say they have enough signatures to put the measure on the ballot.