Legalization Of Cannabis For Adults, Even With Age Limit Of 18, Does NOT Significantly Increase Teen Use

Lest anyone think that the feared massive post-legalization surge in teen cannabis use somehow NOT materializing in the USA (in legalization states) was somehow due to the age limit being set at 21, a recent study found that Canada also did not see a post-legalization surge in teen use either, and their age limit was 18 in Alberta and Quebec and 19 in other provinces at the time of the study (Quebec has unfortunately since raised it to 21 as of January 1, 2020, but the study ended with the 2018-2019 school year while it was still 18).  There was no statistically significant difference between cohorts of students before and after legalization in Canada.  And while Alberta had the highest reported rate of high school cannabis use of the handful of provinces studied, both before and after national legalization in October 2018, Quebec interestingly had the lowest.  And the other two provinces studied (Ontario and British Columbia) were somewhere in between.  

Note that modest short-term increases in occasional or experimental use, by perhaps a few percentage points, are actually to be expected, if only because they will likely be more honest in surveys now.

As for the specious claim that Uruguay (age limit 18) saw an increase in teen cannabis use after legalization in 2013, that claim was based on cherry-picking two arbitrary years:  2003 and 2014, without considering more recent trends.  And even in the Netherlands, there was no increase in teen cannabis use that could be unambiguously linked to their policy of quasi-legalization for adults over 18 since 1976 (note that it was originally 16, just like the drinking and tobacco smoking age once was, in most of the country until 1996).

Point is, just like with alcohol or tobacco, teens who are inclined to use cannabis will do so whether or not it is legal or not for them (or their slightly older near-peers) to do so.  And like alcohol (but unlike tobacco), most of those who experiment with it will not become regular users, let alone problem users or addicts.  And prohibition of either for adults, including young adults, clearly does NOT stop teens from using.

Thus, there is no good reason to set the age limit any higher than 18.  Period.

UPDATE:  Looks like Uruguay actually saw a decrease in cannabis use among youth under 18 following legalization.  For 18-21 year olds, there was a modest short-term increase in 2014, followed by a decrease.  Note that Uruguay set their cannabis age limit at 18.

And back in the States, guess what?  Contrary to the doomsayers, legalization still did not cause an increase in teen cannabis use as of 2023.