Want Teens To Smoke Less Pot? Legalize It - Evolutionary psychology predicted it, data now confirms it.

As of January 2018, twenty-nine U.S. states have legalized the use of marijuana for medical use. Another fourteen have decriminalized possession of the drug, and eight states have fully legalized marijuana even for recreational use. Critics of this trend, including Attorney General Jeff Sessions, have long argued that legalization of marijuana "will lead to more marijuana use, including among children and teens, causing all sorts of public health problems down the line." In short, those favoring strict drug laws believe that, as marijuana becomes more available and less stigmatized, teen drug use will go up. It's a straightforward and logical belief. 

The reality is that, to date, not one jurisdiction, either in the U.S. or elsewhere, has seen a marked increase in teen drug use following the relaxation of marijuana restrictions. Not one. Both Colorado and Washington, the pioneer states of marijuana legalization, have actually seen drops in teen marijuana use following legalization. The drop in Colorado was particularly dramatic. Despite the wave of legalization, nationwide, teen drug use is at a 20-year low.

Nathan H. Lents, Ph.D., in: Psychology Today, 05.02.2018

https://www.psychologytoday.com/blog/beastly-behavior/201802/want-teens-smoke-less-pot-legalize-it