Legalizing Marijuana Doesn't Lead Teens to Smoke More

A young man smokes marijuana from a pipe during the 4/20 Rally at the Civic Center in Denver on April 20, 2014. Mark Leffingwel / REUTERS

Politicians present and past—from current Maryland congressman Andy Harris to former President Richard Nixon—have argued that legalizing marijuana would increase its use among teens. That claim is false, according to the latest science.

A study published June 15 in The Lancet Psychiatry found that adolescents are not more likely to smoke weed in states where it has been legalized for medical reasons than adolescents living in states where it remains prohibited. And surveys suggest more teens are not smoking more in states where it has been outright legalized for recreational use, like Colorado. In fact, youth pot use in Colorado, for example, appears to have dipped since legalization.

The massive paper analyzed information from more than 1 million teens in the continental United States over the course of 24 years, from 1991 to 2014.

"Our findings provide the strongest evidence to date that marijuana use by teenagers does not increase after a state legalizes medical marijuana," said Deborah Hasin, an epidemiologist at the Columbia University Medical Center, in a statement.

The study did find that, on average, more teens smoked pot in states where it has been legalized. But this was true before legalization as well. In other words, the change in the plant's legal status had no significant impact on how many teens decided to light up.