Latest Teen Brain and Cannabis Study More Smoke than Fire

The scary-sounding headline from a few weeks ago in USA Today reads, "Marijuana caused more damage to teens' brains than alcohol, study finds".  Yes, there was a study that claimed to find such results, but there is less here than meets the eye.

In other words, there's more smoke than fire.

The actual study itself is predictably behind a paywall, and we will not dignify such questionable research by paying for it, so we couldn't find the actual numbers and thus could not quantify any effect sizes or how long the reported effects lasted, but the abstract and several news articles summarize qualitatively the main findings.  The study, which involved nearly 4000 students from 7th through 10th grades in the greater Montreal area, longitudinally following them for those four years, asking questions about both alcohol and cannanis use and giving tests on memory and response inhibition.  Statistically significant correlations were noted between increased cannabis use and reduced performance on such tests, while interestingly for alcohol such correlations failed to reach statistical significance.

Again, no information about the size of such reported effects, and guess what?  SIZE MATTERS.  And so does duration.  Also, it say nothing about any such correlations beyond 10th grade, nor clearly distinguish between lighter and heavier use.  (The article did note that there were many more daily users of cannabis than alcohol, despite the fact that there were many more drinkers than tokers overall the sample.)  And it is very curious that the typically pro-21 mainstream scientific community are so willing to practically exonerate alcohol in such a study of teens--or perhaps they are simply alcohol supremacists.  And while the sample size and longitudinal nature of this study puts it head and shoulders about most other studies on the matter, given the aforementioned concerns it should still be viewed with caution in terms of causation.

Additionally, the study seems to be silent on the real "dark horse of drugs"--tobacco/nicotine.  Nicotine is a known neurotoxin, particularly during early adolescence, and is far more correlated with cannabis than alcohol use.  Thus, at least some of the reported effects in the study could in fact be due to tobacco, and/or perhaps other substances as well.

Keep in mind that the infamous 2012 study that reportedly found persistently reduced IQs among adults who used cannabis before age 18, was debunked by 2014 study that found no correlation between adolescent cannabis use and IQ or exam performance (though heavy use beginning before age 15 was associated with slightly poorer exam results at age 16).  This latter study did control for tobacco, alcohol, and a host of other factors.  So it is very likely that soon another study will come a long and refute the first study discussed in this article, or perhaps find that any such effects are limited to the heaviest users, particularly those who began before age 15 or 16.  In fact, a 2018 systematic review of 69 studies of adolescent and young adult cannabis use and cognitive functioning found that reported adverse effects were much smaller in size than the prohibitionists like to claim, and generally tend to be temporary rather than permanent, even for frequent and/or heavy use.  And interestingly, no correlation with age of onset, though the mean age of study participants in these 69 studies was significantly higher than in the aforementioned Montreal study.

Other studies as well cast serious doubt on the scary claims of cannabis neurotoxicity as well, and most studies find weed safer than alcohol.

So what is the best takeaway from such studies?  It would seem that while occasional or moderate cannabis use is basically a non-problem, heavy and/or daily/near-daily use (unless medically necessary) should probably be avoided at any age, but particularly for people under 18 and especially under 15.  And while delaying the onset of use, or at least regular use, for as long as possible is probably wise for people under 18 and especially under 15, there is no hard scientific evidence that cannabis is any more harmful at 18 than it is as 21, 25, or even 30 for that matter.  Thus, there is no good reason to keep it illegal or set the age limit any higher than 18.  And even for people well under 18, the criminal law is still far too harsh a tool to apply to something like this that more likely than not turns out to be a non-problem.