Study: Cannabis Use Not Predictive Of Lower IQ, Poorer Educational Performance

cropsMarijuana use by adolescents is not associated with lower IQ or poorer educational performance once adjustments are made for potential confounders, specifically cigarette smoking, according to longitudinal data published online ahead of print in the Journal of Psychopharmacology.

British investigators assessed the relationship between cumulative cannabis use and IQ at the age of 15 and educational performance at the age of 16 in a cohort of 2,235 adolescents.

After researchers adjusted for potentially confounding variables, such as childhood depression and cigarette use, they reported, “[T]hose who had used cannabis [greater than or equal to] 50 times did not differ from never-users on either IQ or educational performance.”

By contrast, teen cigarette smoking was associated with poorer educational outcomes even after researchers adjusted for other confounding variables.

Researchers concluded, “In summary, the notion that cannabis use itself is causally related to lower IQ and poorer educational performance was not supported in this large teenage sample.”

A widely publicized New Zealand study published in 2012 in The Proceedings of the National Academy of Sciences reported that frequent use of cannabis by those under the age of 18 was associated with lower IQ by age 38. However, a separate review of the data published later in the same journal suggested that the changes were likely the result of socioeconomic differences, not cannabis use.

More recently, the results of a 2015 study in the journal Drug and Alcohol Dependence reported that the effects of persistent adolescent cannabis use on academic performance “became non-significant after controlling for persistent alcohol and tobacco use.”

Full text of the study, “Are IQ and educational outcomes in teenagers related to their cannabis use? A prospective cohort study,” appears online here.

17 thoughts

    1. Conservatives in particular have been poorly served by the Limbaugh/FOX News inspired image of the perpetually incensed, uncivil lowbrow curmudgeon stubbornly clinging to his delusions, eg,:

      1) Climate Change is a hoax perpetuated by a vast, multi-lingual international conspiracy of scientists.

      2) There’s a war on Christmas.

      3) Marijuana is a dangerous Schedule 1 narcotic.

      Persisting with these kinds of delusions serves neither the party or the country. It virtually guarantees wasting money on wild-goose-chases and Ghostbusters.

  1. Not the least surprised by the results of this study. It simply shows what so many of us have already known for years while our Govt has largely ignored us.

  2. The holey moley pall mall war on cannabis alias drugs has posed an inhibiting factor on intellectual development which is the Burden of Secrecy imposed on cannabis users, especially teeners over whom some officious groanups have a domineering supervisory function.

    Using cannabis at all, let alone frequently, imposes a rigamarole of absenting oneself from places (like schools) where the groan-ups are (and thus missing out on some mentoring assistance) and also very cautiously secretly getting to and from the secret place without getting “busted”.

    A child obsessively watchful not to be detected or found out has that much less time left to Investigate, Learn, Practice, Express anything– and a characteristic education deficit Demeanor develops which makes the groan-ups suspicious anyway, leading to bust, prosecution, lifelong individual career blackli$ting, intra-family antagonism and other misfortune opportunisticly blamed on the cannabis by the Paid Prohibitors.

    By the way everybody knew, consciously or not, all this time, that the word “Cigarette” meant $ecret, and a toxic combustion Joint is Easier to Hide From Your Mom or The Cop (up to point of use) than proper vapor-inhalant equipment. $ecrecy itself is a kind of transactional carbon monoxide that dumms everyone and everything down.

  3. So even if the kiddies do get ahold of some, its not going to hurt their brains!?!?!?! Who would’ve thought except all the people who smoked and didn’t get suddenly bad at math.

  4. Marijuana makes me smarter. It got me through college! But the whole time I was growing up, marijuana was the boogy-man: it was going to give you cancer, it was going to give you brain damage, it was going to make you sterile. For every bit of bad judgement or ordinary mistakes I’ve ever made, there was always someone there, shaking their head, saying “must be the marijuana.” For every bit of bad luck I had, someone was there saying “well, that’s what you get for smoking that stuff.” That predudice against me continues to this day! I’ve often joked that if I ever got hit by an asteroid, there would be those who blamed my destruction on my own marijuana use.

    Now it turns out that smoking pot was a really smart move!

    So now where are all those people who, for all those years, said that the single most important thing a person must do is to give up pot? Do they now admit they were wrong? Are they sorry for ruining my career? Fuck no, no they don’t want to talk about it anymore.

    Who’s the dumbass now?

    1. Perhaps what we need is a movie that shows more sophisticated, brilliant career marijuana consumers demonstrating neurogenesis, and not the same old degenerative story we all know about getting drunk and stoned or mixing bad habits like tobacco or crack or whatever.
      I can’t believe looking back that I once thought as a teen that weed “kills your brain cells” because Morgan Freeman said it to a teen in the movie “Lean on Me.” Now Mr. Freeman advocates publically that he uses marijuana to treat his fybromyalgia. Go figure.

      Comedy always seems to try and dumb it down for us like the movie Pineapple Expressway, and there’s certainly a time for Seth Rogan’s level of humor, but we end up with exaggerations of the truth. The only intelligent movie I can recall watching someone smoke a joint to calm down and make a wise decision was Meryl Streep in some movie where shes stressed out and finds a joint in her desk and smokes it. And that’s embarrassing! Not that theres so few intelligent movies about weed, but that I actually admitted watching a movie with Meryl Streep in it.
      We need smart weed movies! Smart can still be funny!

      @Don M; I concur on marijuana improving one’s chess game. Marijuana improves creative strategy, abstract reasoning, and provides vital perspective.

  5. Many of the smartest people I’ve know have been regular cannabis users. Speaking for myself, I have played chess for years but it wasn’t until after using cannabis regularly that I really started to see my ability improve dramatically. It is as though I am now able to see the big picture more clearly in order to more accurately guide my decisions. It’s pretty amazing and probably seems impossible to those that haven’t ever tried it.

    That said, it is important to note that I am an educated responsible adult. I don’t abuse the herb. I use it wisely in small amounts; approximately 1/4 to 1/2 of a joints worth per day to achieve positive results. In addition to increased insights and creativity, I also get the benefit of reduced stress! Experts have said that stress can cause numerous health problems which is why I started using it regularly. As I approach age 60, I am in better than average physical and mental condition!

  6. Recently, the FBI complained because they weren’t able to hire the best computer programmers because they all use marijuana!!!

    Imagine that 🙂

    I used to be a programmer myself. Most of us used it. Honestly, I did much of my best work under the influence; usually in the afternoon after having indulged during lunch break!

  7. Teens playing football should be allowed to consume marijuana. If were going to cheer their concussions we can damn sure provide them the safest most effective neuroprotectant and American pastime.

    With that said, if you have to study or go to school, consume marijuana early in the morning like before a jog, farm work or a long commute. Give yourself a break during work and study hours. Then consume again at the end of the day to reflect on what you have learned and enjoy solving complex problems.

  8. @DonM, Thanks for important chess testimony!

    Note that 1/4 to 1/2 Joint is 125-250 mgs, you are a Candidate for Legalized Possessor and/or Maker of a 25-mg-$ingle-$erving Vape Toke Utensil. 5-10 tokes a day may even be more than most of us need, but by timely SUBSTITUTING for a $igarette Pak-a-day habit–182 “puffs”* a day– it could save 400,000 American lives a year (including some friend of yours or mine).

    * a December 2001 Pall Mall Fool Page Ad in Time Magazine claimed a Pall Mall would deliver 10.8 “puffs” on average, a Marlboro just 9.1. Multiply by 20.

    PS1 The flexdrawtube one-hitter is a hybrid instrument that can be used both to $moke and to Vape, but via the Easy-Learn Heat-Not-Burn Lighter-Management Technique you can at least 90% Vape, the only Combustion is at the end of the toke, burning off some tasty cellulose left over after the Vapors have been orally diligently exvaporized out.

    PS2 Nonviolent tracksport involving the traditional ovoid football but no battle uniforms, helmets etc. Teammembers run along 2-4 parallel tracks, passing and catching the football as they go. They might do a certain distance unit while successfully passing the pigskin 28 or 56 times, for example. It can be made into a dance form and combined with tRackmusik.

    PS3: Consider making SETS of large outdoor chesspieces out of Sanded $crap lumber and deadwoodharvest logs/sticks (some plastic “Staunton” sets sell for $500 on line). See Essential Preschool Eco-Engineering-Eduation Toys for an opensource diagram-cartoon showing a standardized design for constructing the wood chesspieces so each of the 12 (WB x PNBRQK) piece types is infallibly distinguished from the 11 others.

    Customer for above product might be the officer in charge of the Garden at your nearby Public Library, install something for very little kids to do between computer times.

  9. Marijuana seems to attract misfits and people who think different. These people never do well on conventional tests that seem to test conformity as much as anything else. Still I don’t believe marijuana makes them this way it is just that these people get most benefit from it and are willing to do things others consider unacceptable (such as breaking the law).

  10. Cannabis use historically leads to increased socialization, healing therapies, homeostasis, and unfortunately, institutional theft and enslavement.

  11. Now what will SAM do? How can they convince us that rehab is essential since the IQ argument is now proved to be poor propaganda? Let’s see… how about that weed causes man boobs? Yeah, it’s an old one but I can’t think of anything for poor Kevin to use on scared parents. Kevin just needs to switch to a harmful substance and leave cannabis to us adults.

    1. Kevin agrees with those of us who oppose Big Tobacco and Sneakotine addiction, we have to help Kevin understand that the 700-mg Burn-it-all-now Combustion $igarette is the Big Tobacco, the 500-mg Combustion Joint is Big Marijuana, and that both can be replaced with a 25-mg Single Vapetoke flexdrawtube one-hitter Dosage Regulation utensil.

  12. Our city of Modesto CA has just passed regs banning the growth of cannabis in the city. I have conflicting thoughts on the subject. I think there are good benefits medically, my experience in the construction business gives me second thoughts. In 1983 we built a ski condo/commercial project near Purgatory north of Durango CO. 90% of our carpentry crew were college grads. Almost all smoked a joint on break.
    One walked off the second story of a unit onto the first floor.
    Didn’t hurt him, but it was within 20 minutes after the break.
    Two carpenters moved an aluminum ladder away from a building after a break and were electrocuted when, not paying attention, moved a ladder into a power line. One died, the other didn’t work for a year. Our foreman, after coming off a break, cut an $8K glue lam 3 feet short. Three native Americans on the job smoked joints while waiting for their pay checks, went down the road, decided to pass a car on a two lane road and never pulled over when approached by a pickup from the opposite direction. Two of the Indians were killed and two in the pickup. This just one job where I think cannabis contributed to accidents. There are many other stories over the years. My own son smoked in high school and his grades were C’s and D’s. After I tried tough love and sent him packing, he ended up with his mother and her new husband. He stayed off the weed and his grades went to straight A’s. It didn’t hurt his IQ though. He has smoked as an adult and when he does he gets a little nasty. I personally have had a couple of weird experiences and will not use it. We have a friend in his late fifties who smokes quite a bit and it doesn’t seem to bother him. He’s a psychologist. There are other adults we know who smoke weed and are very lackadaisical and not motivated to better themselves and to hold steady jobs.
    So I think this stuff has different effects on different people, but I still won’t hire anyone who uses it.

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