New Study Questions Link Between Heavy Cannabis Use and Declining IQ

A newly published study contradicts the findings from a previous study that suggested that heavy cannabis use as a teenager lowers the person’s IQ by middle age. The new study is titled, “Correlations between cannabis use and IQ change in the Dunedin cohort are consistent with confounding from socioeconomic status” and is published in the current issue of Proceedings of the National Academy of Sciences.

Ole Røgeberg, lead author of the new study and a labor economist at the Ragnar Frisch Center for Economic Research in Oslo, used simulations to show that an alternative confounding model based on time-varying effects of socioeconomic status could explain the previous study’s results. For example, low-income people have reduced access to schooling, regardless of cannabis use.

Røgeberg notes three studies in which cannabis use is not associated with declining IQ, while the previous study’s researchers note that they controlled for socioeconomic status and found that in all socioeconomic categories, the IQs of children who were not heavy users remained unchanged from adolescence to adulthood.

For now, researchers agree that both studies have merit and that more research should be done to further explore the relationship between heavy cannabis use and declining IQ.

To read more about this topic you can view the original story at Nature.

Reference: “Correlations between cannabis use and IQ change in the Dunedin cohort are consistent with confounding from socioeconomic status” by Ole Rogeberg, 14 January 2013, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.1215678110

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