In this Dec. 5, 2013 photo, a worker processes marijuana in the trimming room at the Medicine Man dispensary and grow operation in northeast Denver.Ed Andrieski/The Associated Press
Marijuana has momentum on its side. In the United States, Colorado, Washington and Oregon have already voted to legalize pot. More than a dozen other states could line up to follow suit, through bill, ballot initiative or executive order. In Canada, too, there's a growing discussion over liberalizing the laws.
Colorado opened its pot shops this year, so it's far too early to tell what the impact of legalization will be. In Canada, legalization is playing out as an election issue – with Liberals and Conservatives weighing in on the morality of legalization. What Canadians should be paying more attention to is the science around the effects of marijuana – particularly on the teenage brain.
Those who favour legalization are not proposing to sell pot to teenagers, but there's conflicting data on whether the legal sale of marijuana to adults would lead to increased use by minors. There are arguments on both sides: It could signal to kids that smoking a joint is just as acceptable as having a drink. Would that lead to wider use? Or would the greater regulation that accompanies legal sales make it harder for minors to get marijuana?
Also uncertain are the medical effects of marijuana on the teenage brain. Adolescence is a crucial period of brain development. Some studies have shown early marijuana use permanently alters its course. In extreme cases it has been tied to depression and anxiety. But there are a lot of unknowns, and researchers admit there's still much work to be done.
In the U.S., the conservative right hinged its opposition to legalization on the risk marijuana poses to teens. In several states, they failed to persuade a majority of voters, and so far the sky has not fallen. It remains to be seen whether Stephen Harper's Conservatives will succeed by striking a similar tone. Liberal Leader Justin Trudeau favours legalization; the Tories are running ads saying that poses a threat to kids.
It would be far more useful to focus on what actually matters: Whether it would be possible to liberalize the rules on pot, and simultaneously reduce use, especially teenage use. The experiments going on in Colorado and other U.S. states will offer Canada some clues. Let's use evidence to decide.