Cannabis has been consumed for thousands of years, and scientific research of its physiological effects on the brain has been going on for decades. So why should one particular Feinberg School of Medicine psychiatry study on marijuana use be published and set off a media storm just days before 4/20, or “Weed Day?” It would be remiss to deny a certain uptick in marijuana use on this day, but I wouldn’t be so quick to predict a massive surge of brain damage across the country, and, as it turns out, neither would the research paper, “Cannabis Use is Quantitatively Associated with Nucleus Accumbens and Amygdala Abnormalities in Young Adult Recreational Users.”



A close reading of the study in question reveals some serious limitations that significantly reduce the generalizability of any results found by the researchers. Co-senior study author Dr. Hans Breiter has stated in his interviews to mainstream media outlets like Fox, USA Today and Time that findings of “alterations of the neural matrix of core reward structures” from his study “raises a strong challenge to the idea that casual marijuana use isn’t associated with bad consequences.”

However, no “strong” conclusions can be made at all from the tiny sample size of 40 participants, only 20 of whom were cannabis users. Experimental subjects were deliberately selected to be just as healthy as control subjects, creating a nonrandom sample, and no consideration was given to the possibility that existing brain differences can predispose certain individuals to smoking pot in the first place, serving as the cause of marijuana use instead of the effect. Furthermore, Dr. Breiter’s definition of “casual use” is highly suspect, considering the group of marijuana users studied smoked an average of 11.2 joints per week, an amount that probably hasn’t been casual since Woodstock in the 1960s. Before even examining the results, we should be worried about the researchers’ ability to design a controlled study.

Digging into the data, we confirm that cannabis affects the same limbic dopamine system targeted by alcohol and all other drugs. However, their findings here don’t exactly warrant “severe worry.” The limbic structures in question only exhibited minor changes in shape and density, including some that occasionally even help the brain. We already know from previous research that the brain alters its shape to respond to a changing environment, and such changes of plasticity tend not to be permanent. More notable is that even though these alterations may in fact have unaccounted negative effects on the brain, there is no evidence at all in the study results that any notable structural changes, much less any cognitive abnormalities, were found in the most casual users, those only using marijuana 1-2 times per week. In its conclusion, the paper is right to suggest that any implications arising from the data are highly speculative and require much more robust, longitudinal research before any long-term implications can be identified.

The paper’s generally unexciting results leave us to question in awe the incredible media frenzy that surrounded its publication. I believe this may stem from America’s longstanding distrust of science, which is only exacerbated when drugs like marijuana are involved. We ignore and misinterpret scientific findings at our own peril. Dr. Breiter expresses “worry (that) we haven’t studied this compound,” when, in fact, we do know a fair bit about cannabis after years of research both inside and outside of the U.S., from which we’ve learned many good and bad things about this ancient plant. Even more worrisome, though, is that we routinely forget the most important lesson in science and statistics: Correlation does not equal causation. Dr. Breiter is not justified in saying “People think a little recreational use shouldn’t cause a problem if someone is doing OK with work or school. Our data directly says this is not the case,” because the study does not establish that marijuana causes anything, and the press fails to recognize these glaring limitations of the study.

So now it falls upon us to be the discerning readers and “weed” out the faulty science from the valid and rigorously tested science, the sensational media from the cautious and skeptical media. Even if some scientists may be opinionated and try to grab undeserved headlines from a scientifically illiterate press, not all of them are, and we as a public need to recognize the differences. With regards to marijuana, we know a good deal about the positives (relaxation, appetite stimulation) and the negatives (memory loss, potential for dependence), so using involves a calculated risk. If you do smoke next 4/20, know what you’re doing, drink lots of water and just to be safe, try to stay under 11.2 joints.

Rex Tai is a Weinberg junior and the co-president of Students for Sensible Drug Policy. He can be reached at [email protected]. If you would like to respond publicly to this column, send a Letter to the Editor to [email protected].

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