The point is, I have been, at times, a total stoner. So, I mean: I get weed. I get it. But I quit smoking awhile ago, and now I think it sucks. Smoking weed all the time is a huge drain on your finances. And what do you do when you smoke weed? You sit on the couch, watch a movie or play a video game, and spend more money on a bunch of gross food that you later feel gross about. What did you get out of it? Impaired motor abilities?
Short-term memory loss? I guess. I dunno. Thus, studies comparing smokers with nonsmokers at a moment in time are of limited use: Maybe pot caused the cognitive effects you might find, or maybe some other factor explains the difference.
To truly tease out the effect of marijuana alone, researchers have to follow people over time, ideally gathering information about their cognition and intelligence before they began using pot. Only a handful of studies have done this so far. The first, published in the journal Neurotoxicology and Teratology in , found that being a current regular user of marijuana led to deficits in memory, IQ, processing speed and memory, but people who had used the drug in the past but had since stopped did not show long-term effects three months after quitting.
However, that study followed teenagers who used marijuana for an average of only two years. A bigger, longer-term study, published in the journal Proceedings of the National Academy of Sciences in August , did not bode well for pot connoisseurs. Researchers followed 1, New Zealanders from birth to age 38, assessing their cognitive function at age 13 before any participants had started using cannabis and again at age Participants reported their cannabis use at age 18, 21, 26, 32 and 38, giving researchers an opportunity to determine whether cognitive effects differed depending on when a person started using marijuana and how long he or she continued to use it.
That study found global declines in cognition, including an average drop in IQ of about 6 points in people who had used marijuana. The biggest effects were seen in persistent users — people who reported having consumed marijuana in at least three interviews between the ages of 18 and Notably, the deficits were not found in people who started using marijuana as adults, but were strong in people who took up the habit as teens.
The researchers also had participants' close friends or family members fill out questionnaires on the participants' daily functioning, and found that those who had used marijuana were worse off than those who had not.
Not all of the longitudinal data agrees, however. For a study published in the Journal of Psychopharmacology in January , researchers followed 2, British teenagers, about a quarter of whom had tried pot at least once by age The researchers found no link between cumulative marijuana exposure at age 15 and IQ or educational performance at age The study was based on a short time frame, but even longer-lasting investigations returned conflicting results. In February , researchers published the results of a study following marijuana users and nonusers into middle age.
About 84 percent 2, had used marijuana at some point, but only 11 percent had used it in middle age. The study showed that after the researchers accounted for other factors that could have affected the results, such as other drug use and demographics, cumulative pot use was linked to worse verbal memory.
For every five years of marijuana use, a person would remember one less word, on average, from a list of 15 they were asked to memorize. However, no declines in executive function or processing speed were found.
Although all of these studies controlled for factors that might influence cognition — demographics, other drug use, education — those statistics aren't an exact science. Jackson, along with University of Minnesota Twin Cities researcher Joshua Isen, came up with a way to control the comparison.
The researchers were working with two data sets of more than 3, identical twins, meaning they had the same genetic makeup and the same home environment.
Sign up. Password recovery. The Fresh Toast The most trusted name in cannabis. Monday, October 25, Here's What Experts Say. Does Marijuana Make You Stupid? By: Al Olson. July 14, Tags cannabis highway marijuana medical marijuana science.
Heart disease is the leading cause of death in the U. The reality is that studies suggest little likelihood of a connections between cannabis consumption and decreased IQ.
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