In Colorado, 12.6 percent of 12- to 17-year-olds used marijuana monthly in the combined years 2013 and 2014, up slightly from 11.2 percent in 2012-2013. (SAMHSA combines years for state-level estimates to increase the sample size.) Similarly, in Washington, the monthly teen marijuana use rate was 10.1 percent in 2013-2014, compared with 9.8 percent in 2012-2013.
Proponents and opponents of marijuana legalization gave different interpretations of the changing teen use rates.
"This data, combined with other federally-funded research released this week, shows that what our opponents say about legalization leading to skyrocketing youth marijuana use just isn't true," Tom Angell of Marijuana Majority, a pro-legalization group, said in an email.
Another recent federal survey of drug use among high school students found marijuana use was flat nationwide this year.
But legalization opponents pointed out that due partly to decreases in use in other states, Colorado now leads the nation in monthly adolescent marijuana use. "Now that Colorado has legalized and widely commercialized marijuana, their children use marijuana regularly more than children in any other state," said Kevin Sabet of Smart Approaches to Marijuana, an anti-legalization group.
Public health experts say the latest numbers are not particularly suggestive one way or another. "Most of the legal changes have pertained only to those 21 and over, so the absence of a big increase in teens is exactly what you’d expect," said Jonathan Caulkins of Carnegie Mellon University. "So it seems to me that the non-response of teens to the non-legalization for teens really tells us very little about the effects of legalization."
Like the national survey that came out earlier this month, the state-level data show significant decreases in the percentage of teens who say there's a "great risk of harm from smoking marijuana once a month." This has traditionally been understood as a risk factor for increased marijuana use -- if kids don't think pot is harmful, they'll be more likely to try it.
But that pattern hasn't held true over the past few years. Perceptions of risk are decreasing, and use among teens is flat. "Maybe this cohort is just plain well-behaved, but not being afraid of pot doesn't seem to be leading them to use a lot of it," Kleiman said.
Caulkins noted that teens have been saying that marijuana is easily available for decades now. "The availability reported in [the Monitoring the Future Survey] was already very high 20 years ago, so the liberalization couldn’t do much more to increase availability. And it has not changed legal risk or consequences for teens," he said.