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Marijuana IQ Study: No Real Link Between Weed and Lower Intelligence in Teens

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By    |   Wednesday, 20 Jan 2016 08:32 AM

A marijuana IQ study comparing teenage twin siblings who either used or abstained from weed for 10 years found no measurable link between use of the drug and lower IQ scores.

Nicholas Jackson, lead study researcher from the University of Southern California, told Science magazine that most studies that linked marijuana to things like memory loss and low IQ were often single snapshots and not representative of the drug's impact over time.

The new study, published Tuesday in the Proceedings of the National Academy of Sciences, followed a large group of teen drug users over an extended period of time.

"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," the study stated in its abstract.

"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.

The PNAS study found little difference in the IQs of marijuana-using teenage twins and their non-using siblings, suggesting that there may have been other factors at work in past studies that implied that marijuana affected IQ.

"Marijuana users had lower test scores relative to nonusers and showed a significant decline in crystallized intelligence between preadolescence and late adolescence," the PNAS study stated in its abstract.

"However, there was no evidence of a dose-response relationship between frequency of use and intelligence quotient (IQ) change. Furthermore, marijuana-using twins failed to show significantly greater IQ decline relative to their abstinent siblings. Evidence from these two samples suggests that observed declines in measured IQ may not be a direct result of marijuana exposure but rather attributable to familial factors that underlie both marijuana initiation and low intellectual attainment," the study continued.

Another study published Jan. 6 in the Journal of Psychopharmacology stated that "modest cannabis use in teenagers may have less cognitive impact than epidemiological surveys of older cohorts have previously suggested."

"This is a very well-conducted study . . . and a welcome addition to the literature," Valerie Curran, a co-author of the Journal of Psychopharmacology study, said of the new PNAS research in Science magazine.

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A marijuana IQ study comparing teenage twin siblings who either used or abstained from weed for 10 years found no measurable link between use of the drug and lower IQ scores.
marijuana, iq, study, twins, teens
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2016-32-20
Wednesday, 20 Jan 2016 08:32 AM
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