When in doubt, lead with the bold claim—and worry about substantiating it, or addressing the crucial context that could contradict it completely, sometime later.
This is the trap into which “The Science of Learning” columnist Claudia Wallis, a respected veteran science journalist with impeccable credentials, falls in her piece headlined “How legalizing marijuana could hurt student achievement.”
Such an easily digestible takeaway no doubt generated many clicks and shares among those for whom the link between legal marijuana availability—not use, mind you, but the mere presence of legal cannabis in regulated storefronts as opposed to solely in the pockets of street hustlers—and poor academic performance is an irrefutable truth.
It also served as a convenient distraction from the heart of the matter, the nuance that also snares academic reviews: It is next to impossible to finger marijuana by itself as the cause of a general decline or boost in academic performance—not when there’s a host of other variables to weigh.
The test case here is Maastricht, a city in the Netherlands that in 2011 banned its 13 marijuana-dispensing coffeeshops from selling cannabis to foreign nationals. We’re not told how many of the students from other countries studying at the local university were patronizing these establishments—but at least some of them were, one assumes.
All we know is that after the ban, the percentage of foreign students passing their exams increased from 73.9 percent to 77.9 percent, according to the study, which was published in March. “A sizable jump,” Wallis writes.
At last, the neat conclusion that weed hurts students can be drawn. Rather than fall into the “correlation is not causation” traps that have weakened other studies with the necessary caveats, “we could cleanly identify the causal impact of a drug policy,” study co-author Ulf Zoelitz told Wallis.
This is an extremely bold claim—one of the boldest of them of all.
Because, parsing the publicly available abstract and summations of the study (alas, the genuine item is caged behind a paywall), it does not appear that they were able to control for a host of other factors—all of which are more encompassing and far more compounding than the availability of legal weed in the vicinity.
This is the same trap that all studies that purport to declare, with authority, what cannabis does to student performance.
Wallis does address this.
“It’s maddeningly difficult to separate the impact of cannabis from other factors, such as poverty and childhood trauma, which increase the odds of using marijuana and which themselves can directly alter the brain,” she wrote.
A 2015 Arizona State University study also encountered the problem of isolating marijuana from other, perhaps greater factors. Researchers could not weigh the impact of marijuana use independent of alcohol or tobacco consumption.
“The problem is that adolescents who use marijuana tend to also use alcohol and smoke tobacco,” psychologist Madeline Meier, who worked on the study, told Wallis.
Also unclear was whether the students were spending too much time playing video games, which might help academic performance, or wasting study hours scrolling through Instagram or looking for articles on Twitter, which apparently hurts students outcomes.
Every foray into weed and learning should lead with these disclaimers. They won’t, because nuance is boring and confusing. Get to the meat! Get to the viral headline! And so it goes.
But since you’re still here: What exactly, is the link between cannabis legalization and a drop in academic performance? Is it cognitive impairment, is it de-motivation, is it a change in brain chemistry, in reward systems—or something else?
Wallis won’t say—because she can’t. Nobody can—not even the academics studying how marijuana changes the body’s endocannabinoid system, which uses naturally-produced compounds similar to marijuana to regulate a host of human functions.
“(N)o one can say for sure that cannabis disrupts this system, and even less clear is the impact of short-term or moderate use,” she admits.
In the absence of incontrovertible fact, she opts instead for petty and ham-fisted moralizing.
“Obviously, students who are actively high in class are not doing themselves any favors,” she writes. “There’s a rich scientific literature demonstrating that learning, memory and attention all take a hit from cannabis intoxication.”
Yes, of course. This is not up for debate.
Someone stoned in class might not be at the top of their game. This is also not the issue—because this is not a phenomenon peculiar to marijuana. Someone drunk or hungover or tired or on their sixth energy drink while in class may also be similarly impaired. And yet there is a marked dearth of concerned moralizers asking us to tug the reins and slow down those wagons while halting the progress of legalization.
Buried, as well, is another takeaway that shows how damaging marijuana propaganda has been. Researchers pointed to the trend of marijuana legalization being associated with teens’ diminished perception that the drug is dangerous as some kind of trouble.
This should not be misinterpreted. Yet, it almost always is.
Remember how dangerous marijuana has been purported to be—for generations—and remember how false those claims have turned out to be.
Of course legalization should compel teens and everyone else to reconsider cannabis’s true nature; it is nowhere near as harmful as the decades of propaganda have insisted. This is the problem with telling and then attempting to maintain an obvious lie. It leads directly to response bias. If you lied about marijuana’s deadliness, why wouldn’t you lie about its negative impact on my studies?
There is at least one study whose model accounts for demographics, trauma and other mitigating or compounding factors. It, too, found that student performance dipped when cannabis use spiked. At the same time, research on marijuana and the developing brain is far from conclusive. “Significant, long-term effects” of use—including light use—is still unclear.
Suffice to say that teens should be discouraged from dabbing their faces off—nobody serious is saying this is something they should do. The legal age to use marijuana in states where it is available is 21 for a reason–the same reason why that’s the legal age to buy alcohol.
These are the best practices we cautiously employ when embarking on the experiment to legalize marijuana. (Surely, the impacts of banning the substance and arresting 1.5 million people a year for it, including parents and students, is disruptive as well!) To lead with a practiced insouciance that cannabis use by itself could be the sole reason why grades go up or down without an entire story’s worth of context—like what we present about—may make for neat copy, but it’s misleading and irresponsible.