A marijuana IQ study is questioning the long-held belief that use of pot leads to a decline in young people’s IQ. While studies have previously reported on the link between marijuana use and a decline in intelligence, a new study from the University of Southern California shows that the relationship may not be as clear-cut as once believed.
Reports Healthy Day on Jan. 18, via MSN News: “Confounding family issues that lead a kid to try pot in the first place may be to blame for any brain drain, according to the new study. The researchers did report that marijuana users had lower IQ test scores, on average, when compared to those who didn’t indulge in pot. But they also discovered that a twin who uses pot winds up with about the same IQ as a twin who doesn’t.”
The study, published Tuesday in the Proceedings of the National Academy of Sciences, stated in its abstract: “Marijuana is one of the most commonly used drugs in the United States, and use during adolescence — when the brain is still developing — has been proposed as a cause of poorer neurocognitive outcome.”
However, researchers found that in the case of teenaged twins, other factors likely contributed to differences in the IQs. “Nonetheless, research on this topic is scarce and often shows conflicting results, with some studies showing detrimental effects of marijuana use on cognitive functioning and others showing no significant long-term effects,” the study continued.
Statistics show about half of all American youths will try pot at some point in their teenage years, and although there are multiple studies that suggest the drug will interfere with a maturing adolescent brain, USC researchers point out that most studies are a snapshot of time only, and fail to look at the long-term effects of put use.
Scientists have now analyzed the impact of long-term marijuana use in teens, focusing on nearly 800 pairs of twin siblings and using one, non-pot using twin as a control group, over a period of ten years, to measure their cognitive abilities. Researchers found no measurable link between marijuana use and a lower IQ.
Statistician and lead author Nicholas Jackson from the University of Southern California said previous studies often made it impossible to determine which came first – pot use or the decline in one’s IQ. “It’s a classic chicken-egg scenario,” Jackson said, according to Science Magazine.
Adds ScienceMag.org: “Marijuana users lost about four IQ points over the course of the study. But their abstinent twin siblings showed a similar pattern of decline, suggesting that the loss of mental sharpness was due to something other than pot.”
According to Jackson, “this ‘something else’ is related to something about the shared environment of the twins, which would include home, school, and peers,” although he did add that “this does not mean that heavy use in adolescence is problem-free. We desperately need more research on the effects that marijuana has on the brain.”