Dude, good news for the pot smokers among us: Marijuana might not make us dopey, after all. A recent study contradicts a finding from 2012 that linked heavy cannabis use to dwindling IQ. Who to trust in this reefer madness? We break down the pot-head debate.
What’s the Deal?
Marijuana has been in the news of late thanks to its legalization in states across the country. But not all press is good press: Last year, ganja drew a bad rap thanks to one study suggesting people who smoked pot on a regular basis as teenagers were more likely to see declines in their IQ by middle age.
But the new year brings new, weed-friendly findings: A study published yesterday concludes that non-pot-related factors are the real cause of a decline in smarts. The study’s authors propose that factors associated with socioeconomic status — rather than a person’s toking habits — could explain the results of the 2012 study. For example, people in lower socioeconomic classes tend to have reduced access to schooling, which can negatively affect IQ, regardless of cannabis use.
To reach this conclusion, the study’s authors simulated the 2012 study (which followed 1,037 individuals, born the same year, from birth to age 38). Instead of looking for marijuana’s impact, the new study looked just at socioeconomic factors and found the same decline in IQ.
Is It Legit?
Quite possibly. While the 2012 study wasn’t entirely incorrect (people’s cognitive performance did decline over time), it’s a big stretch to attribute those results strictly to a penchant for blowing haze — especially because several studies have found marijuana use isn’t associated with long-term or permanent declines in IQ Current and former marijuana use: preliminary findings of a longitudinal study of effects on IQ in young adults. Fried, P., Watkinson, B., James, D., et al. Canadian Medical Association Journal, 2002 April 2; 166(7): 887–891 Neurocognitive consequences of marihuana—a comparison with pre-drug performance. Fried, PA, Watkinson, B., and Gray, R. Department of Psychology, Carleton University. Neurotoxicology and Teratology, 2005 Mar-Apr;27(2):231-9. Epub 2004 Dec 9 Neuropsychological performance in long-term cannabis users. Pope, HG Jr., Gruber, AJ, Hudson, JI, et al. McLean Hospital, Harvard Medical School. Archives of General Psychiatry, 2001 Oct;58(10):909-15.
That said, some of these same studies found regular heavy users can experience temporary declines in IQ while using marijuana heavily (which perhaps might explain the "dumb stoner" stereotype). This could account for the missing link between the two studies Neurocognitive consequences of marihuana—a comparison with pre-drug performance. Fried, PA, Watkinson, B., and Gray, R. Department of Psychology, Carleton University. Neurotoxicology and Teratology, 2005 Mar-Apr;27(2):231-9. Epub 2004 Dec 9 Neuropsychological performance in long-term cannabis users. Pope, HG Jr., Gruber, AJ, Hudson, JI, et al. McLean Hospital, Harvard Medical School. Archives of General Psychiatry, 2001 Oct;58(10):909-15.
But while research lends credence to the current study’s claims that socioeconomic factors are the real cause of cognitive decline, an author of the 2012 study maintains she and her co-authors controlled for socioeconomic status before drawing their conclusions. Her team also found the IQs of adolescents who weren’t heavy users didn’t change in adulthood — regardless of their socioeconomic background. We can’t discredit the 2012 study entirely.
But the new findings are still cause for marijuana worrywarts to, you know, relax, man.
Are you convinced, or should pot smokers still fear for their cognitive health? Share in the comments below or get in touch with the author on Twitter @LauraNewc.