Unfortunately, marijuana producers have a strong incentive to hook young users. While about 9 percent of adults who use cannabis become addicted, the rate is 17 percent for people who start smoking in their teens, according to NIDA figures. And as the tobacco and alcohol industries have demonstrated, she says, such companies make the majority of their profits on a relatively small proportion of chronic users. "The minute there's a profit motive, companies tend to make a product more addictive," says Lisdahl. "I think legalization is moving ahead prematurely without considering the lessons we've learned from nicotine and alcohol prevention policy research."