Teen marijuana use fell sharply in Colorado in the years 2014 and 2015, after the opening of that state’s recreational marijuana market, new federal survey data show.

The state-level data from the National Survey on Drug Use and Health showed that 18.35 percent of Coloradans ages 12 to 17 had used marijuana in the past year in 2014 or 2015, down sharply from 20.81 percent in 2013/2014. (In this survey, years are paired for state-level data to provide larger sample sizes). That works out to roughly a 12 percent drop in marijuana use, year-over-year.

Year-over-year teen marijuana use fell in most states during that time period, including in Washington, the other state to open recreational marijuana markets in 2014. But that drop wasn’t statistically significant.

Conversely, adult marijuana use rose significantly in Colorado over the same time period. Among Coloradans ages 26 and older, past-year marijuana use rose from 16.80 percent in 2013/2014 to 19.91 percent in 2014/2015. Annual adult marijuana use was up in most states during the same time frame. The legal marijuana markets in Colorado, Washington and elsewhere feature strict age and purchasing limits. [Read more at Washington Post]