Some people have feared that cannabis legalization might cause an increase in teen tokage, but it turns out that, for teen marijuana use, changes in public policy aren’t nearly as big as a factor as advertising. A study last year by the National Survey on Drug Use and Health actually showed that cannabis use among peeps aged 12 to 17 is actually at a 20-year low, even as half the states in America have legalized medical marijuana and eight more legalized it fully.

But a new study from the RAND Corporation finds that advertising for medical marijuana actually does cause more teenagers to use cannabis. The study was led by Elizabeth D’Amico, published Wednesday in the medical journal Drug and Alcohol Dependence and reported on by Leafly.

“Adolescents that reported higher than average exposure to MM [medical marijuana] ads also tended to report greater marijuana use, stronger intentions to use marijuana in the future, stronger positive expectancies about marijuana use, and more negative consequences from use,” the study said.

It also said that teen use of alcohol and tobacco increase in a similar way corresponding to an uptick in advertising for those products.

The study was taken by questioning roughly 2,500 students from 2008 to 2017, from when the participants were 11 or 12 years old in seventh grade until when they were about 19 at the end of high school. Twice as many participants took part in the study when it first started and they were very young, but over the years many of them moved away or just lost interest.

One thing RAND knows for sure is that there are more cannabis advertisements right now than at any point in history. In 2010, only 25% of teenagers had seen at least one cannabis law. In 2017, that number has shot up to 70%.

“Overall, results suggest that exposure to MM advertising may not only play a significant role in shaping attitudes about marijuana, but may also contribute to increased marijuana use and related negative consequences throughout adolescence,” the study showed.

Photo via Flickr user Petra Bensted