Delaying pot smoking to age 17 is better for teens' brains, a new study suggests

Adolescents who smoke marijuana as early as 14 do worse by 20 on some cognitive tests and drop out of school at a higher rate than non-smokers. But if they hold off until age 17, they're less at risk, and performed equally well as adolescents who did not use cannabis.
http://nouvelles.umontreal.ca/en/article/2017/01/24/-d994f54a11/