1/3/2024 0 Comments You stupid sound effect![]() After an injury at Boeing, I went back to Jr college to learn HVAC engineering. Also got the highest test score in senior physics class, as the only junior, after ditching class for the first month, (just started smoking that summer). Scored over 87%, up to 96% on all 5 GED test in high school after I starting using pot. The Takeaway: This study can’t rule out the possibility that marijuana hurts teenagers’ brains, especially in ways that show up only after decades. Also, some twins dropped out of the research if they were greater users than those who stayed, the study would have missed a possible effect of heavy marijuana use. And since the researchers didn’t measure working memory or executive function (judgment, decision-making ability, and other higher cognitive skills), they couldn’t rule out marijuana’s effect on those. If the drug has only a minor effect, this study might have been too small to find it. Second Take: Although the findings challenge the idea that marijuana use hurts cognitive ability, it’s not the final word. That is, whatever spurred teenagers to start using also hurt their IQ. Instead, it suggests that any drop in brain function is not from the drug but from “factors that underlie both marijuana initiation and low intellectual attainment” and are present in both twins’ lives. “This fails to support the implication of the study that adolescent use of marijuana causes neurocognitive declines,” the researchers wrote in PNAS. The strongest evidence against the idea that marijuana is neurotoxic was that marijuana-using twins showed no greater IQ decline than their non-using siblings. 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 reflect truancy, conscientiousness, and other factors apart from inherent cognitive ability and brain function. That also undermines the idea that marijuana impairs cognition. And measures of so-called inherent intelligence, like problem-solving, didn’t fall in users on some measures, like puzzle-solving, scores actually rose. But more frequent marijuana use wasn’t associated with greater IQ decline, as you’d expect if marijuana were toxic to brain function. Overall, users’ IQ dropped 4 points relative to non-users over the study period. In hundreds of cases, one twin smoked and the other didn’t. The twins underwent standard intelligence tests at ages 9 to 12 and again at 17 to 20, and reported whether or not they smoked marijuana (60 percent in California and 36 percent in Minnesota did). Other studies, but fewer, find no long-term association between marijuana and IQ, like this one from Canada in 2005 and this 2004 research on twins by scientists at Boston University.įirst Take: The new PNAS study is also observational, but with an important twist: It zeroes in on that “third factor” possibility by studying twins, 789 in California and 2,277 in Minnesota. Given those limitations, it almost doesn’t matter what the studies have found, but here’s a sampling: marijuana use is associated with decreased intelligence, a 2007 study from New Zealand found or with poorer memory, according to a 1996 study of Costa Rican men and a 2002 US study of long-term users or with poorer attention and verbal skills, a 2010 study reported. And all the studies have been observational - assigning some people to smoke marijuana and others to abstain would yield cleaner results but is obviously unethical. ![]() Most studies have compared marijuana users to non-users at a single point in time, and so can’t assess how marijuana changes brain function over the years any observed differences might have always existed, marijuana or not. According to 2015 government data, 15 percent of 10th graders and 21 percent of 12th graders have used marijuana in the past month. The Backstory: Research on how marijuana affects the developing brain goes back decades, but has heated up as more US states decriminalize or legalize the drug for adults. The Claim: Smoking marijuana does not make teenagers stupid, concludes a study in the current Proceedings of the National Academy of Sciences, contrary to other research that linked getting stoned to impaired cognitive function in adolescents. Gut Check is a periodic look at health claims made by studies, newsmakers, or conventional wisdom. ![]() Exclusive analysis of biotech, pharma, and the life sciences Learn More
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