Not Smoking Marijuana Does This You You Funny
Does smoking pot really make you stupid?
Gut Cheque is a periodic look at health claims made by studies, newsmakers, or conventional wisdom. We ask: Should you believe this?
The Claim: Smoking marijuana does not make teenagers stupid, concludes a study in the electric current Proceedings of the National University of Sciences, contrary to other enquiry that linked getting stoned to impaired cerebral function in adolescents.
The Backstory: Research on how marijuana affects the developing brain goes back decades, only has heated upwards as more US states decriminalize or legalize the drug for adults. According to 2015 government information, xv per centum of tenth graders and 21 per centum of twelfth graders have used marijuana in the past month.
Most studies have compared marijuana users to non-users at a single betoken in time, then can't assess how marijuana changes brain role over the years; any observed differences might take e'er existed, marijuana or not. And all the studies take been observational — assigning some people to fume marijuana and others to abstain would yield cleaner results just is obviously unethical. Given those limitations, it about doesn't matter what the studies take institute, but here'southward a sampling: marijuana utilize is associated with decreased intelligence, a 2007 study from New Zealand constitute; or with poorer memory, co-ordinate to a 1996 study of Costa Rican men and a 2002 US written report of long-term users; or with poorer attention and verbal skills, a 2010 study reported. Other studies, but fewer, notice no long-term association between marijuana and IQ, similar this one from Canada in 2005 and this 2004 research on twins by scientists at Boston University.
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In a key paper from 2012 — it was the largest and longest-running study to date, testing ane,037 people at age 13 and 38 — scientists at Duke Academy found a dramatic drop in intelligence among long-term marijuana users "suggestive of a neurotoxic event of cannabis on the adolescent brain," they wrote in PNAS.
Every bit is ofttimes the case, even reputable researchers publishing in reputable journals run cruel over the deviation between correlation (two phenomena become together) and causation (one causes the other). One 2015 paper declared that "regular cannabis use in adolescence approximately doubles the risks of … cerebral impairment." No: At nigh, such utilize is associated with impairment. Observational inquiry cannot rule out the possibility that a tertiary factor causes both cognitive decline and marijuana use.
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First Take: The new PNAS study is also observational, but with an of import twist: It zeroes in on that "third cistron" possibility by studying twins, 789 in California and two,277 in Minnesota. The twins underwent standard intelligence tests at ages nine to 12 and again at 17 to xx, and reported whether or non they smoked marijuana (60 percentage in California and 36 per centum in Minnesota did). In hundreds of cases, one twin smoked and the other didn't.
Overall, users' IQ dropped four points relative to non-users over the study period. But more than frequent marijuana use wasn't associated with greater IQ decline, as yous'd expect if marijuana were toxic to brain function. And measures of so-called inherent intelligence, similar problem-solving, didn't fall in users; on some measures, like puzzle-solving, scores actually rose. That also undermines the thought that marijuana impairs cognition. Instead, said co-author Joshua Isen of the University of Minnesota, it suggests that something was going on "in how much information they were absorbing," which can reverberate truancy, conscientiousness, and other factors apart from inherent cerebral ability and brain part.
The strongest bear witness against the idea that marijuana is neurotoxic was that marijuana-using twins showed no greater IQ reject than their non-using siblings. "This fails to support the implication of the [2012] written report that adolescent use of marijuana causes neurocognitive declines," the researchers wrote in PNAS. Instead, it suggests that any drop in encephalon office is non from the drug but from "factors that underlie both marijuana initiation and low intellectual attainment" and are nowadays in both twins' lives.
That is, whatever spurred teenagers to start using also injure their IQ.
Second Accept: Although the findings challenge the idea that marijuana use hurts cognitive ability, it'south not the final word. If the drug has but a minor effect, this written report might have been likewise modest to discover information technology. And since the researchers didn't measure working memory or executive function (judgment, decision-making power, and other college cognitive skills), they couldn't rule out marijuana's event on those. Besides, some twins dropped out of the inquiry; if they were greater users than those who stayed, the report would have missed a possible event of heavy marijuana employ.
The Takeaway: This written report can't rule out the possibility that marijuana hurts teenagers' brains, especially in ways that prove up only after decades. But it undermines claims that information technology does.
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Source: https://www.statnews.com/2016/01/19/marijuana-pot-weed-intelligence/
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