After being mostly legalized in Washington and Colorado, marijuana is becoming a trendier news topic with every passing day. And when a topic is trending in the 24-hour news cycle, you can be sure that scientific studies are soon to follow. What greater influence on those who award the grants is there?
One common argument for the legalization of pot is that it isn’t harmful to human health; or at the very least, not as harmful as alcohol, a substance that was only illegal for a brief, dark period in human history in a very backward corner of the globe.
Whether or not the substance is addictive is, to me at least, an open question. A website from the NIH reports that marijuana is addictive to about 9 percent of users, raising to 17 percent in teenage users and 25-50 percent in daily users. Then again, they also report the “withdrawal” symptoms of irritability, sleeplessness, anxiety and drug craving, all of which my wife exhibits after a couple of days without chocolate and seem less of a problem than someone going through caffeine withdrawal.
But I’m not here to make judgments or assumptions; I’m just here to report the facts. According to a recent study from Northwestern University, there is at least one health concern that might be worth taking into account when decriminalizing this controlled substance, and that’s age.
As many studies have shown, at least some of the wiring in the human brain continues to develop well into the early 20s. We are born with a massive number of jumbled connections that slowly get either strengthened or pruned as we experience the world around us. Sufficed to say, those experiences have an impact on how our wiring takes shape and the ability for it to change years later down the line. So introducing any type of chemical that might affect how these wires are crossed is an issue well worth considering.
In the new study, researchers looked at the brains of 97 individuals who partook in daily THC doses in their late teens or early twenties for several years, but had since stopped the habit. They used fMRI machines to trace the connections made deep within the brain’s white matter.
A thin layer of neurons at the surface of the brain called the cortex is where most of the actual computation is going on at any given time. Called grey matter, these brain cells are responsible for seeing, hearing, memory, emotions, speech, decision making, and self-control, to name a few, and consume 95 percent of the oxygen that is sent to your noggin.
By contrast, white matter mostly makes up the interior of your brain and acts more or less as connections between the different areas on the surface. They make crucial communication pathways between your emotional center, decision-making center and muscle control functions, for example. How else are you going to binge eat after watching the Red Wedding for a tenth time?
It is these wires or connections that the researchers mapped out. And what they found was that those who had previously used marijuana on a daily basis had distinctly different white matter patterns than those who did not. What’s more, those changes bore a striking resemblance to disparities found in those suffering from schizophrenia—a condition whose strength of affliction has been linked to marijuana use in previous studies. It has also been linked to a poor working memory, which predicts poor academic performance and everyday functioning.
Now, of course, this study is not definitive. What if the marijuana users had these subtle differences in brain wiring before they started smoking? What if these differences are actually part of the reason they started in the first place? Or maybe there’s some other confounding factor that links the dozens of subjects together?
Some sort of long-term longitudinal study would be need to tease out the exact implications, meaning they’d have to map a lot of people’s brain before they started smoking as well as years afterward and compare them to similar controls. And who knows? Maybe that might be possible if more states legalize the practice.
But for now, if I were a neuroscience graduate student studying in Colorado or Washington, I know exactly what study I’d be proposing for my thesis.
The study, “Cannabis-Related Working Memory Deficits and Associated Subcortical Morphological Differences in Healthy Individuals and Schizophrenia Subjects,” was published in the journal Schizophrenia Bulletin by senior co-author John G. Csernansky, chair of psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine and Northwestern Memorial Hospital.