New scientific research has shown that teenage pot use may not lower IQ, as previously thought.
A recent study by the National Academy of Science compared IQ changes in twin siblings who either used or abstained from marijuana for a 10-year period. After considering environmental factors, they found no measurable link between marijuana use and lower IQ. They did conclude that any decline in I.Q. was more attributable to familial factors.
This same type of study was being done simultaneously by the University College of London with more than 2000 (non-twin) British teenagers; with a similar conclusion.
These studies are in direct opposition to a 2012 Duke University study that concluded persistent marijuana use by adolescents resulted in a noticeable decline in their cognitive therapy. (In other words, it made them stupid – just like the 1987 antidrug PSA said it would.)
So what’s a parent to do? Before giving a green light to teen toking, critics of the studies have pointed out that the studies failed to rule out other potential explanations for the decline in IQ, such as a teen’s family environment, whether they dropped out of school, or how much marijuana they actually consumed.
“While it is possible that the findings are absolutely accurate,” said Oregon Health & Science University psychiatrist Sarah Feldstein Ewing. Other shortfalls, she says included a “missed opportunity to get a truly fine-grained analysis” of the contribution of cannabis and other substances to IQ.”
And even NAS clinicians say it’s too soon to make over-arching statements about marijuana use and teens. Statistician Nicholas Jackson of the University of Southern California in Los Angeles, lead author of the NAS study, says, “emerging evidence” that marijuana does not erode IQ.”
“This does not mean that heavy use in adolescence is problem-free,” he says, adding, “We desperately need more research on the effects that marijuana has on the brain. Unfortunately these types of studies are nearly impossible due to federal restrictions.”
For now, he concludes, “I’m mostly concerned about what’s going on in the child’s environment, that a 14-year-old is seeking refuge in drugs.”