Weed Doesn’t Cause Low IQ, Shoddy Science Does


WASHINGTON POST: Now, a new study out from the University College of London provides even stronger evidence that the Duke [study’s] findings [that marijuana causes low IQs] were flawed. The study draws on a considerably larger sample of adolescents than the Duke research – 2,612 children born in the Bristol area of the U.K. in 1991 and 1992. Researchers examined children’s IQ scores at age 8 and again at age 15, and found “no relationship between cannabis use and lower IQ at age 15,” when confounding factors – alcohol use, cigarette use, maternal education, and others – were taken into account. Even heavy marijuana use wasn’t associated with IQ. “In particular alcohol use was found to be strongly associated with IQ decline,” the authors write. “No other factors were found to be predictive of IQ change.” MORE

INTERNATIONAL BUSINESS TIMES: The findings will be presented at the European College of Neuropsychopharmacology annual congress in Berlin. The chair of the annual congress, Guy Goodwin, from the University of Oxford, told BBC News: “This is a potentially important study because it suggests that the current focus on the alleged harms of cannabis may be obscuring the fact that its use is often correlated with that of other even more freely available drugs and possibly lifestyle factors.” MORE