A recent study, published in the Canadian Medical Association Journal, examined whether marijuana lowered intelligence levels in users. The study was largely ignored by US media, while within Canada, the results seemed to depend on which newspaper headline you read.
Most headlines about the study said something like “Potheads become dopes” (Toronto Sun) or “Pot does rot your brain” (Edmonton Sun). Yet a few papers reported the opposite, announcing that “Marijuana Doesn’t Make You A Dope” (Calgary Herald) or “Smoking Pot No Risk To IQ” (Globe & Mail).
That a single study could produce such conflicting headlines says more about the integrity of the media than it does about the study itself.
Here’s how the study was done: A group of young, middle-class adults was assembled, consisting of non-tokers, light pot smokers, and heavy users. Light users were those who smoked less than five joints a week, heavy users toked an average of 33 joints each week. Researchers used urine samples to confirm marijuana use or abstinence.
Everyone in the study had been subjected to IQ tests between the ages of nine and twelve. They subjected this crew to follow-up IQ tests to see how their lifetime use of marijuana might have affected their IQ. They found that the non-tokers IQ’s stayed the same or went up slightly. The light tokers had an average IQ increase of five points, more than the non-tokers. The heavy users had suffered an IQ loss of about four points.
The study further found that after abstaining from weed for three months the differences between the three groups’ IQ levels disappeared.
The study was led by Dr Paul Fried at Carleton University in Ottawa, who told the media that they needed to be “very cautious” about the results.
What this study would seem to show is that moderate use of cannabis produces an increase in IQ, while heavy use produces a decrease. Further, the study shows that even heavy, long term use of cannabis produces no permanent harm to IQ scores.
This study refutes most of the prohibitionist propaganda about youth and cannabis use. That the “light users” who toked five joints per week actually saw an increase in IQ scores indicates that cannabis may have enhancing effects on learning and comprehension. That both the benefit to light tokers and the deficit to heavy tokers is temporary is reassuring because it shows that the effects of cannabis on the brain are easily reversed, even among heavy, long-term users.
Meanwhile, a separate US study into marijuana use and cognition found similar results. Led by Dr Constantine Lyketsos of John Hopkins University in Baltimore, the study analyzed test results of over 1300 adults on a test called the Mini-Mental State Examination. They compared two tests given 11 1/2 years apart. In an article published in the April American Journal of Epidemiology, the authors found that the light and heavy toking groups had about the same or less age-related cognitive decline than the non-tokers.
At Cannabis Culture we’d like to see further research into the enhancement effects of cannabis use. It seems plausible that cannabis use also enhances artistic comprehension, integration of novel ideas, pattern recognition and holistic thinking.