As marijuana legalization spreads across the United States, opponents have maintained that there will be negative long-term consequences, especially on young people. On Monday, for example, anti-pot activist Kevin Sabet tweeted“young adult use has skyrocketed over the past 10 years.”

There’s just one problem: The latest federal data says the opposite is true. Weed use by teens is dropping, especially in states that allow recreational marijuana use. The National Survey on Drug Use and Health, an annual nationwide survey, found declines in teen marijuana use in all but one of the five states that had legal weed from 2014 to 2016.

Colorado sold more than a billion dollars worth of weed last year, but the number of teens who reported smoking pot in the past year there dropped from around 18 percent to 16 percent, with a similar drop — from 11 percent to 9 percent — in teens reporting they’d smoked in the past month.

Other states saw similar declines or no major change in yearly use, including Washington, D.C. (16 percent  to 13 percent), Oregon (17 percent to 17 percent), and Washington state (15 percent to 13.5 percent), while underaged smoking ticked up just barely in Alaska (18.44 percent to 18.86 percent).

It’s still unclear why this is happening. It could be that teens are deciding that smoking weed is uncool because they’re seeing their parents do it, or it could be that states with recreational marijuana laws often employ public health campaigns designed to discourage young people from getting high. Or maybe it’s something else entirely. [Read more at VICE]