A new analysis is challenging a report that suggests regular marijuana smoking during the teen years can lead to a long-term drop in IQ.
The author of the new paper says pot might not have anything to do with the mental decline seen in the original study, and that other factors may be to blame.
The original study included more than 1,000 people who’d been born in the town of Dunedin, New Zealand. Their IQ was tested at ages 13 and 38, and they were asked about marijuana use periodically between those ages.
Participants who said they were dependent on pot by age 18 showed a drop in IQ score between ages 13 and 38, according to researchers at Duke University and elsewhere. Their report, which got wide attention last August, suggested pot is harmful to the adolescent brain.
Not so fast, says the new analysis, published online Monday by the Proceedings of the National Academy of Sciences.
Ole Rogeberg of the Ragnar Frisch Center for Economic Research in Oslo, says the IQ trend might have emerged from differences among the study participants in socioeconomic factors like income, education and occupation.
He based his paper on a computer simulation. Drawing on results of earlier research, It traced the potential effects of those socioeconomic factors on IQ. He found patterns that looked just like what the Duke study found for smoking marijuana.
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