Study: Cannabis Use Not Associated With Deficits In Intelligence Quotient

Moderate cannabis consumption by young people is not positively associated with changes in intelligence quotient (IQ), according to data presented this week at the European College of Neuropsychopharmacology annual congress in Berlin, Germany.

Investigators at the University College of London analyzed data from 2,612 subjects who had their IQ tested at the age of eight and again at age 15. They reported no relationship between cannabis use and lower IQ at age 15 when confounding factors such as subjects’ history of alcohol use and cigarette use were taken into account.

“In particular alcohol use was found to be strongly associated with IQ decline,” the authors wrote in a press release cited by The Washington Post. “No other factors were found to be predictive of IQ change.”

Quoted in the Independent Business Times, the study’s lead author said: “Our findings suggest cannabis may not have a detrimental effect on cognition, once we account for other related factors particularly cigarette and alcohol use. This may suggest that previous research findings showing poorer cognitive performance in cannabis users may have resulted from the lifestyle, behavior and personal history typically associated with cannabis use, rather than cannabis use itself.”

The investigators acknowledged that more chronic marijuana use, defined in the study as a subject’s admission of having consumed cannabis 50 times or more by age 15, was correlated with slightly poorer exam results at the age of 16 — even after controlling for other variables. However, investigators admitted: “It’s hard to know what causes what. Do kids do badly at school because they are smoking weed, or do they smoke weed because they’re doing badly?”

Commenting on the newly presented data, the meeting’s Chair, Guy Goodwin, from the University of Oxford, told BBC News: “This is a potentially important study because it suggests that the current focus on the alleged harms of cannabis may be obscuring the fact that its use is often correlated with that of other even more freely available drugs and possibly lifestyle factors.”

In a recent review published in the New England Journal of Medicine, the NIDA Director Nora Volkow alleged that cannabis use, particularly by adolescents, is associated with brain alterations and lower IQ. However, the IQ study cited by Ms. Volkow as the basis of her claim was later questioned in a separate analysis published in the Proceedings of the National Academy of Sciences. That paper suggested that socioeconomics, not subjects’ cannabis use, was responsible for differences in IQ and that the plant’s “true effect [on intelligence quotient] could be zero.”

A previous assessment of cannabis use and its potential impact on intelligence quotient in a cohort of young people tracked since birth reported, “[M]arijuana does not have a long-term negative impact on global intelligence.”

20 thoughts

  1. this is an unrelated issue yet id like to see an validated accomidation such as braiding seven differential strains of cannabis to develop an new age tye stick sort of program an adjust the needed individuals medications in the dark ages due to horrible tactics actual tree braiding was outlawed due to census issuances an outher belittling reasons

  2. A final sword in the Bull from prohibitionists’ last line of defense; “Oh the poor children’s brain cells.”
    I love this line:
    “It’s hard to know what causes what. Do kids do badly at school because they are smoking weed, or do they smoke weed because they’re doing badly?” Even a raccoon understands marijuana is medicine. And even recreation is a form of therapy. What doesn’t kill you makes you stronger… and apparently smarter.

    That quote reminds me of this girl I knew in high school who was asking a boy she hadn’t seen where he had been. He replied, “In High School.” She said, “Tch, you didn’t got to high school; You went to school HIGH!” I was 17 and had decided to deliberately stay away from weed because I believed all the concern about brain cells. After marijuana cut my cigarette habit, knocked me out of my depression and improved my perspective and thinking, I quickly realized how wrong I had been.
    Marijuana, especially for first time consumers, stimulates long term sub conscious thought to surface to one’s attention, such as listening to a certain type of music or reading a certain type of book we have been prohibiting from ourselves for the priority of work and school curriculum. First time users may even confront fears they have been suppressing, causing a perception of paranoia among some users. Although this is part of a natural neurological healing process (Supressing memories is bad for you) these impulsive subconscious memories and thoughts surfacing at random can be distracting when one is trying to consume and regurgitate short-term information to pass some exam… an exam, for example, designed to make us into “good” doctors by learning nothing about the endocannabinoid system by leading us into contrived careers selling pharmaceuticals for the next 30 years of our lives just so we can pay off our student loan debt.
    (Unless marijuana provides you with the adequate perspective and motivation to start your own business):-)
    I still think the ONDCP forcing Denver to create those “lab rat” anti-marijuana ads while ignoring the epidemic that pills, alcohol and heroin are causing among our youth to be another revolting example of our government’s hypocritical drug policy.

    Consuming marijuana either early before school hours our after school hours improves cognitive reasoning, abstract reasoning, stimulates social and play behavior vital to creative development and acquisition of more advanced social skills and increased overall neurological function and health. This does not even take into account what tumors or neurodegenerative diseases the marijuana could be treating that we don’t even know we were developing prior to consumption. We can’t even overdose on it!

    I recommend strains such as trainwreck, a sativa strain that contains a high amount of pinenes that stimulate alert consciousness and awareness, balanced by a fair amount of anti-psychoactive CBDs that improve overall cognitive function.
    Indica strains, are better reserved for relaxing in the evenings after study hours as they produce less of a head high and more of a body high that can cause more of a couch-lock effect. And if you’re mixing your weed with alcohol, your IQ test is void.

    The medicinal legalization and fair commercial taxation of recreation marijuana will inspire a Green Age of American innovation and socioeconomic equality that will improve the health and quality of life of the entire planet for generations to come. And we can do it all while we’re stoned.

  3. I’m a victim of the state foster care system, and the product of the insane asylums we call public schools. Where I went to school in small town Utah in the 70’s there were NO drugs whatsoever in that school I swear! Noon time hallway scene was a madhouse, wedgies and toilet head dunking’s were everyday routine, and lets not forget that old favorite the trip up from behind. Now about socioeconomic factors, because I was a drop-out.

  4. education /cannabis = thrown out of school is there answer , The authorities have a easy campaign there justice is to simply keep you form an education so they throw you out did it to me even now at work in The new England regional carpenters local 107 bunch of prohibitionist bastards don’t care if you good trade person you have to follow the rank and file asshole if not throw you out of work detail , there will continue to not allow this member employment for 4 years now .. even as I given proof drug testing does not work , jack Dohahue Jim turner are prohibitionist care not for truth ,

  5. Great to see.

    In my heart I’ve known it to only be a matter of time until the prohibitionist’s run out of legitimate concerns regarding cannabis. They’re already recycling old reefer madness myths but at least each one is promptly countered by science.

    After all… prohibs allege that cannabis is harmful to the mind of adolescents. If I’m not mistaken this was solely due to brain scans showing differences in brain activity between cannabis users and those who abstain. But what if those differences were actually beneficial?

    Mind you also, cannabis has been scientifically proven to be a potent antioxidant and neuroprotectant. See patent #6630507. Look at the related studies between reversing neurodegenerative conditions and antioxidant therapy. Consider also that as cannabis stimulates neurogenesis (creation of new neurons in the brain) and potentially, this herb becomes a great option for preserving the mind and cognition over time.

    Now for a step into the deep end, consider that cannabis is a potent antioxidant which by definition mitigates or reduces oxidative stress. Do a quick ‘net search to see which modern diseases are rooted in oxidative stress – most if not all including cancer! The implications go vastly beyond protecting the mind.

    While prohibs maintain reefer madness propaganda, science is rapidly confirming the anecdotal evidence we’ve had for years – cannabis is one of the best plant-based, healthful longevity substances on the planet.

    I cannot condone the non-medical use of cannabis in youths, however we must consider that the effects may actually be health-promoting rather than deleterious. Especially in comparison to harmful drugs, such as alcohol and tobacco.

  6. The oligarchs fear kids learning HOW TO USE cannabis effectively because it will doom the high-profit addictive nicotine $igarette format ($4000 a year in high-tax states which they want every possible kid to get hooked on).

    Using early before school hours is actually a good strategy every other day or every few days combined with skipping breakfast except water or one thorough chewing of all the calcium in an orange or grapefruit. Then think the word SMOOTH to avoid forgetting and letting some sudden outburst of concern or enthusiasm make others suspicious of you.

    In my view omitting “relaxing in the evening” tokes altogether is a good strategy because it provides an abstinence period off which the good morning tokes are more effective (measured in LEAP Long-term Episodic Associative Performance memoryprofusion). Put ingesting cannabis in front of challenging productivity and learning rather than in front of lounging.

  7. @ Julian, ““It’s hard to know what causes what. Do kids do badly at school because they are smoking weed, or do they smoke weed because they’re doing badly?” Even a raccoon understands marijuana is medicine. And even recreation is a form of therapy. What doesn’t kill you makes you stronger… and apparently smarter.”

    Look, marijuana might stimulate better cognition is some people, while depressing cognitive development in other people. No one that has a bad reaction to using marijuana needs to feel like they aren’t normal. I mean they aren’t Norml, but that’s different. Maybe they are, like you say realizing things they were trying to repress and for those people marijuana can be therapeutic on a mental/emotional level, but only if they are in a supportive environment at the time. They need to learn how to deal with their demons before going out somewhere and bugging out.

    But for some, they really just don’t like marijuana. Maybe their bodies are telling them something…?

    Look at VotR’s experience, people don’t need drugs to excuse outrageous behavior: a boorish attitude and some aggression is all it takes.

  8. Personal cannabis consumption is just that, and should not be on anyones radar, except the individuals practicing moderate and respectful interaction with one of the planet’s most diverse and useful participants.

  9. As Dr. King might have said, I Have a Scheme–

    1. Practical Service– Reforest the Planet or minister to those who do;

    2. Education– learn how to Reforest the planet, minister etc.;

    3. Art– exercise the self-Education organs, mental and physical;

    4. Therapy– relieve conditions which block exercise, Art, Education, Eco-productivity;

    5. Entertainment– relieve despair, boredom, anxiety or other conditions which block Therapy.

    As @Julian said, “Recreation is a form of therapy”– maybe it can even rise to the stature of art or education– but at very least it can do service temporarily as Entertainment when that is needed or justified. Accordingly vote YES on Nov. 4.

    Note: Dr. Mark Kleiman is having a WEBINAR Monday Oct. 27 I think mainly regarding how to structure cannabis control and regulation in the legalized systems existing in CO and WA and proposed for OR AK DC FL– and I personally selfinterestedly hope anyone who agrees with me the libertarianest way to achieve that is through moderation and regulation instructively embodied in the ingestion-related serving utensils– vaporizers or long-stemmed one-hitters– will promptly send suggestions to Dr. Kleiman and his staff.

    “Consuming… early before school hours… improves cognitive reasoning, abstract reasoning [etc.].” AGREED! but also suggest advise kids to SKIP the later-in-day “relaxing in evening” stuff in order to sharpen PAEP previous-abstinence-effect-premium the next morning! (Plus, every TWO days has advantages over every day– it takes about 47 hours to most magnificently recharge the Neuronic Creative Paranoia Batteries.)

  10. Apology for any repetitiousnessities, not seeing that the earlier comment had posted I jumped the gun.

  11. @ Dave Evans and Mexweed,

    Certainly we are all wired differently, with different physiologies, but we all need to play, laugh, love and recreate. One of the subtle yet powerful benefits of marijuana that gets overlooked, especially for those with PTSD, is that we are compelled to talk about our pain whereas we otherwise would not socialize.
    This is a vital, serious tool for people struggling with repressive memories, PTSD, or depression.
    I don’t believe marijuana gets enough credit in the way it forces us to face our demons, talk about our problems where many veterans of war would otherwise submit to painkillers, and basically get us to laugh and play, which are as vital to human emotional and intellectual development as sleeping and eating.

  12. What I find is that cannabis allows a person’s mind to remain alert and inquisitive as opposed to alcohol which dulls and reduces a person’s intellect. In this way cannabis has a positive effect on intelligence throughout life.

  13. I think your mind wouldn’t fit in a small box the size of the head, and therefore your brain isn’t how we think and exhibit more or less intellect than another person. So, why care what weed does to the brain?

  14. This proves the prohibitionists are the ones with the low IQ. I smoked from 15 to 35 & scored highest IQ on the education counsel test ever when I was 32. It increased my creativity & kept my tension under control.

  15. Sounds like alcohol does affect mental performance, but marijuana does not.

    That sound about right to me.

  16. I had consumed small amounts of cannabis responsibly for 32years. Cannabis has eased times of tension and anxiety as well as quelling bouts of a.d.d I have dealt with since my childhood. It has brought me great peace while increasing my ability to complete many tasks that normally I would not be able to focus on long enough to complete. I have a great, loving family as well as a good job of 37years. I have excellent credit and own my home as well as two vehicles.
    Their are millions of good, successful, happy people who consume cannabis ( and it does not take money to be successful). I hope someone who is looking for a good reason to feel differently about cannabis will read real life stories from those of us who have had a great adult life while consuming a great part of life given free to grow from the green earth! Peace to you all!

  17. There have been countless studies regarding the impact of marijuana use, and most prove that there aren’t that many negative effects. Why is there such a stress on marijuana use? Alcohol is a drug, and even has a worse effect than marijuana does. The war on drugs needs to end now.

  18. Yeah Mexweed,

    The media messages people everyday, telling them that marijuana is used for being lazy. It is such a pervasive attitude that even some potheads believe it and even internalize the endless negative propaganda.

  19. The media are paid for by adverti$ers who want everyone to be propagandized into maximum laziness so they will PAY some corporation to make them “vicariously” happy instead of turn off the TV and enjoy some CREATIVE REUSE HANDWORK in a wood(/word)working studio.

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