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Study Shows Marijuana Use In Teens Correlates To Decreasing IQ 626

Posted by timothy
from the news-for-long-term-nerds dept.
retroworks writes "The BBC reports on a paper published in the U.S.'s Proceedings of the National Academy of Sciences showing a correlation between persistent, regular cannabis use and risk of lower IQ. The study finds the risk particularly correlates use of cannabis by teenagers who use the drug "four times a week year after year." The more people smoked, the greater the loss in IQ. Reviewers of the study at King's College Institute of Psychiatry states that the data and methodology are exceptional, but she also cautions that there may be another explanation, such as depression, which could lower IQ while stimulating marijuana use. The study does not mention or rule out 'nocebo' effects, i.e. just feeling stupid for spending your teens hanging out with potheads."
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Study Shows Marijuana Use In Teens Correlates To Decreasing IQ

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  • Mods (Score:3, Insightful)

    by Anonymous Coward on Tuesday August 28, 2012 @08:14AM (#41147513)

    Tag news article 'Propaganda'

    • Re:Mods (Score:5, Insightful)

      by i kan reed (749298) on Tuesday August 28, 2012 @08:31AM (#41147711) Homepage Journal

      Propaganda by whom, and for what purpose? How do you identify it as propaganda instead of legitimate science? You have to answer these basic questions and support your answers with evidence before anybody is going to buy into your conspiracy theories.

      • Re:Mods (Score:5, Funny)

        by jeffmeden (135043) on Tuesday August 28, 2012 @08:37AM (#41147815) Homepage Journal

        Propaganda by whom, and for what purpose? How do you identify it as propaganda instead of legitimate science? You have to answer these basic questions and support your answers with evidence before anybody is going to buy into your conspiracy theories.

        Propaganda; n. Any material which proposes to sway a reader to form a conclusion that conflicts with your own.

      • Re: (Score:3, Interesting)

        The knee-jerk is a conditioned response from seeing a host of studies that clearly are propaganda. Nearly every study that says something bad is. This one is legit, but I can understand how it'd be easy to miss; the main reason I feel it's on the level is that it succeeds in muddying its own stance.
        • Re:Mods (Score:4, Informative)

          by TheRealMindChild (743925) on Tuesday August 28, 2012 @12:05PM (#41151277) Homepage Journal
          No. First, let us look at this little tidbit:

          Having taken into account other factors such as alcohol or tobacco dependency or other drug use, as well the number of years spent in education...

          So there was manipulation of the data to exclude the effect of these "other factors", which completely throws out any correlation that these could/would/should have. It would be akin to testing if teen pregnancy lowered IQ, but they threw out data belonging to private school girls.

          they found that those who persistently used cannabis - smoking it at least four times a week year after year through their teens, 20s and, in some cases, their 30s - suffered a decline in their IQ.

          This is plain bad science. These people they are studying are CHRONIC users. They are likely using right up to the morning of their "interview". It is like the kid who started smoking cigarettes at 8 years old vs. someone starting at, say 23. The former is most likely to smoke 2+ packs a day. The latter usually smokes less than one pack. Also, nothing has been done to show what happens when they would stop.

          I get my data through observation of people throughout my life from all sorts of geography. I absolutely believe that my retort has as much of a proper sampling as 1000 people from New Zealand
      • by betterunixthanunix (980855) on Tuesday August 28, 2012 @10:07AM (#41149313)
        Scientific conclusion: heavy marijuana use amongst teenagers is correlated with decreasing IQ.

        Propaganda: MARIJUANA LOWERS IQ

        The difference is in how this is presented. A scientific presentation cannot possibly say that marijuana is a causal factor until at least all of the following are addressed:
        1. What can cause IQ to change over time? As someone else pointed out, it is entirely possible that sitting around doing nothing all day will lower IQ, and so marijuana's role may just be in discouraging teenagers from participating in activities that maintain or increase their IQ. Marijuana can increase appetite -- it is possible that eating too much junk food lowers IQ.
        2. There may be a particular trait that attracts some teenagers to smoke pot heavily, which also causes them to have lower IQs later in life.
        3. Teenagers who smoke marijuana may be participants in a subculture that involves other activities that cause lower IQ.
        4. Marijuana may be produced using fertilizers or pesticides that are also absorbed when the drug is used, and those might cause lower IQ.
        5. Marijuana smoke may contain chemicals that cause lower IQ; maybe other methods of taking the drug will not have such an effect (or maybe other methods are even worse).

        There are a lot of things that can cause the results the scientists saw -- which is good news for them, since it means they have plenty of questions to answer. Unfortunately, the media will see this, ignore the part about heavy users, spend no time discussing confounding factors, and jump right on the "marijuana is bad" bandwagon. Typical, unsurprising, propaganda-driven approach.

        • by Belial6 (794905) on Tuesday August 28, 2012 @11:11AM (#41150343)

          As someone else pointed out, it is entirely possible that sitting around doing nothing all day will lower IQ, and so marijuana's role may just be in discouraging teenagers from participating in activities that maintain or increase their IQ.

          I have always heavily suspected that this is the single biggest issue with "marijuana making you dumb". We see the same kinds of effects with people who have other, non-intellectual hobbies that they over indulge in. (sleeping, reading romance novels, playing sports, etc..., etc..., etc...) I'm pretty sure that we have some strong evidence that mental stimulation makes people smarter than they would be without it.

        • by tobiah (308208) on Tuesday August 28, 2012 @11:19AM (#41150465)

          Perhaps it's just that low IQ is correlated with answering "yes" on a marijuana survey.

      • Re:Mods (Score:5, Informative)

        by composer777 (175489) * on Tuesday August 28, 2012 @11:24AM (#41150547)

        You should study the history of anti-drug research. One of the original studies that claimed marijuana caused severe brain damaged basically put face masks on monkeys and had them inhaling nothing but smoke for a significant period of time. The cause of the brain damage was CO poisoning and general hypoxia, which should have been obvious to anyone with half a brain. No one breathes nothing but smoke when they smoke. That's what a lot of studies do, they give a subject 100x the dose that is used, or use some unusual delivery method, and perform the study on it, drawing absurd conclusions that aren't event remotely scientific.

        The purpose? Funding, plain and simple. Studies that are anti-drug get lots of funding, and those that aren't, don't get approved (by the DEA when performed on humans) or funded. Why? Because the government funds the studies and the drug war is a political tool that they need evidence to support. A huge amount of science is shaped and steered through funding, and it absolutely biases the results.

        If you are reasonably intelligent, this shouldn't surprise you. We've had quacks for the entire history of science and medicine, and many of them have used science to explain what is clearly a politically motivated status quo. Just look at all the studies that assumed minorities were inferior, and proposed to find out why (by measuring brain volume and other anatomical characteristics), without first checking the assumption that minorities were inferior.

  • News Flash (Score:4, Insightful)

    by Lumpy (12016) on Tuesday August 28, 2012 @08:15AM (#41147521) Homepage

    Drinking Wine or Beer 4 times a day year after year will reduce your IQ. Over use of ANYTHING will cause problems.

    • Re:News Flash (Score:5, Insightful)

      by sonamchauhan (587356) <sonamc@noSPam.gmail.com> on Tuesday August 28, 2012 @08:19AM (#41147567) Journal

      4 times a week, not 4 times a day.

    • Re:News Flash (Score:5, Interesting)

      by TemperedAlchemist (2045966) on Tuesday August 28, 2012 @08:37AM (#41147821)

      Do you have any evidence to support that assertion?

      The medical community has known for some time that marijuana has adverse effects. For one reason or another, the pot smoking community seems to get all defensive and denies all allegations backed by science almost as fiercely as denial of global warming or evolution.

      It would be nice to see more studies like this and see if these results can be replicated.

      • Re:News Flash (Score:5, Insightful)

        by CanHasDIY (1672858) on Tuesday August 28, 2012 @09:37AM (#41148783) Homepage Journal

        Do you have any evidence to support that assertion?

        The medical community has known for some time that marijuana has adverse effects.

        Lol, it never fails to amuse me when someone lambastes another for making an un-backed statement without citing any evidence... moments before they themselves make an un-backed statement without citing any evidence.

        To that end, who is this 'medical community' of which you speak, and what are these 'adverse affects' you so ambiguously refer to?

        • Maybe he meant TFA?
      • Re:News Flash (Score:5, Insightful)

        by mikael_j (106439) on Tuesday August 28, 2012 @09:45AM (#41148915)

        In my experience most of those in favor of cannabis legalization aren't blind to the adverse effects, it's just that they're sick to death of seeing time and time again how some study proclaims "Teenagers who are genetically predisposed to end up with severe mental illness may have slightly earlier onset of their condition if they smoke marijuana on a daily basis" and how the media and those who fervently hate cannabis turn that into "POT MAKES YOU CRAZY!".

      • Re:News Flash (Score:5, Informative)

        by schlachter (862210) on Tuesday August 28, 2012 @09:45AM (#41148917)

        The pot smoking community has released their official response to this study, saying, "dude, chill with the anti pot stuff."

      • Re:News Flash (Score:5, Insightful)

        by Hatta (162192) on Tuesday August 28, 2012 @10:15AM (#41149449) Journal

        For one reason or another, the pot smoking community seems to get all defensive and denies all allegations backed by science almost as fiercely as denial of global warming or evolution.

        We don't deny that there are adverse effects. We deny that the adverse effects are sufficient enough to justify imprisioning people. Life is full of risks, and the fun parts even more so. A country that allows people to ride motorcycles [wikipedia.org] for recreation has no place telling us Cannabis is too unsafe for recreation.

    • Re: (Score:2, Funny)

      by Anonymous Coward

      If it makes you less intelligent, it probably makes you happier too. Ignorance is, after all, bliss.

    • Re:News Flash (Score:5, Insightful)

      by Radres (776901) on Tuesday August 28, 2012 @09:05AM (#41148251)

      But pot use after age 18 doesn't have long-term affects on IQ, only for the time immediately after consuming the drug. This was an important point lost in the summary. So, marijuana should be illegal for young kids to smoke. If marijuana were legal and regulated like alcohol, we would see less young people abusing the drug.

      • by mooingyak (720677)

        But pot use after age 18 doesn't have long-term affects on IQ, only for the time immediately after consuming the drug. This was an important point lost in the summary. So, marijuana should be illegal for young kids to smoke.

        Agreed.

        If marijuana were legal and regulated like alcohol, we would see less young people abusing the drug.

        So we should change things to that it's no longer legal to sell marijuana to minors?

      • Re:News Flash (Score:4, Insightful)

        by slim (1652) <john AT hartnup DOT net> on Tuesday August 28, 2012 @10:01AM (#41149213) Homepage

        So, marijuana should be illegal for young kids to smoke

        It *is* illegal for young kids to smoke marijuana (and for anyone else).

        The problem here is that there isn't a direct link between "it's illegal" and "people cease to do it". Prohibiting drug use has demonstrably failed to stop people wanting to use drugs, and has demonstrably failed to prevent them from doing so. It's even possible that prohibition has made it *easier* for people to get hold of drugs, since production, distribution and retail is in the hands of people who aren't beholden to the usual rules.

        Make it legal, such that illicit supply is no longer profitable. Regulate and educate, so that kids (and adults) generally don't want to use, kids that want to can't find a supply, adults that want to have a trustworthy supply and a society that encourages sensible usage levels.

  • Updated for a new generation.

  • Ya buddy (Score:5, Funny)

    by Metabolife (961249) on Tuesday August 28, 2012 @08:19AM (#41147571)

    I was gonna go to class, before I got high
    I coulda' cheated and I coulda passed, but I got high
    I'm taking it next semester and I know why, (why man) 'cuz I got high
    Because I got high
    Because I got high

  • Work ethic... (Score:5, Interesting)

    by shakezula (842399) on Tuesday August 28, 2012 @08:20AM (#41147575) Homepage
    I'd say the biggest drawback to pot smoking in teenage years is a lack of ability to find and keep a job. Being a loaf isn't conducive to paying the bills, which is the skill teenagers need to learn first and foremost. Self-sufficiency is paramount to heading off to college, or work, or simply moving on in life and I'd wager is more important than grades, social status, or if they are pot-heads or not. Its possible to smoke weed and still have a reasonable income, but the desire to be self-sufficient needs to come first or the stoner mentality wins over.
    • by DogDude (805747)
      What does smoking pot have to do with employment?
      • Re:Work ethic... (Score:5, Informative)

        by Dr_Barnowl (709838) on Tuesday August 28, 2012 @08:46AM (#41147947)

        It demotivates you. I've lived with stoners and they were some of the most lackadaisical folks I've met. If you're not going to get up off your ass and get a job, and prove that you want to keep it, you're not going to be employed, simple as that.

        My POV on the IQ loss is that there's probably a heavy component of just not exercising the mind, because you can't be bothered.

  • Confounding (Score:4, Interesting)

    by Anonymous Coward on Tuesday August 28, 2012 @08:21AM (#41147583)

    Does smoking pot as a teen lower your IQ, or are stupid teens more likely to smoke pot?

    • Re:Confounding (Score:5, Informative)

      by stranger_to_himself (1132241) on Tuesday August 28, 2012 @08:55AM (#41148059) Journal

      It was a longitudinal study. First assessment was before anybody had smoked anything, and it was the change in IQ that was tracked.

    • Re:Confounding (Score:5, Informative)

      by radtea (464814) on Tuesday August 28, 2012 @09:11AM (#41148355)

      Does smoking pot as a teen lower your IQ, or are stupid teens more likely to smoke pot?

      From the abstract; "Impairment was concentrated among adolescent-onset cannabis users, with more persistent use associated with greater decline. Further, cessation of cannabis use did not fully restore neuropsychological functioning among adolescent-onset cannabis users. Findings are suggestive of a neurotoxic effect of cannabis on the adolescent brain and highlight the importance of prevention and policy efforts targeting adolescents."

      A randomized controlled trial is by far the best means of proving causality, but a strong dose-response curve is a good secondary indicator. In this case, the data don't seem to support the contention of the abstract very well. Here they are from Table 1 in the paper:

      Persistence of regular cannabis use
      Never used | 242 | 38.84 | 99.84 (14.39) | 100.64 (15.25) | 0.05
      Used, never regularly | 508 | 50.59 | 102.27 (13.59) | 101.24 (14.81) | â'0.07
      Used regularly at 1 wave | 47 | 72.34 | 101.42 (14.41) | 98.45 (14.89) | â'0.20
      Used regularly at 2 waves | 36 | 63.89 | 95.28 (10.74) | 93.26 (11.44) | â'0.13
      Used regularly at 3+ waves | 41 | 78.05 | 96.00 (16.06) | 90.77 (13.88) | â'0.35

      Where the columns are: MJ usage category, # of people in category, %male, Avg(SD) IQ at 7- 13 years old, Avg(SD) IQ at 38 years old, size of effect.

      There are a couple of striking things: the percentage of males jumps markedly as the regularity of cannabis use goes up, and the initial IQ drops. So this study shows that young men with slighlty lower than average IQ are more likely to engage in regular cannabis use, and this may or may not result in a further decrease in their IQ over time.

      Also, the numbers in the regular use categories are quite small: a few dozen.

      I've not read the paper in detail, but superficially this looks exactly like the kind of research that led to hormone replacement therapy being touted as a good thing for post-menapausal women. Selection effects amongst the population of HRT users in the early days resulted in apparently dramatically improved health outcomes, whereas when applied to the general population the results were just the opposite.

      While the data are plausibly suggestive that cannabis is bad for the adolescent brain, it is also plausibly suggestive that the lower-IQ male adolescent is more at risk for cannibis use and IQ decline.

    • by Baloroth (2370816)

      Probably both, but the study shows the former. From the abstract:

      Persistent cannabis use was associated with neuropsychological decline broadly across domains of functioning, even after controlling for years of education. Informants also reported noticing more cognitive problems for persistent cannabis users. Impairment was concentrated among adolescent-onset cannabis users, with more persistent use associated with greater decline. Further, cessation of cannabis use did not fully restore neuropsychological functioning among adolescent-onset cannabis users. Findings are suggestive of a neurotoxic effect of cannabis on the adolescent brain and highlight the importance of prevention and policy efforts targeting adolescents.

      They followed individuals for several decades, and frequent users showed a decline of neuropsychological functioning that non-pot-smokers did not. In other words, pot damages your brain. Note that they were specifically testing adolescent-onset users: in other words, people who used it as teenagers. Whether it would have the same effects on an adult who didn't smoke it as a teen isn't answered (although probably yes, I'm guessing the effects

  • ... bears shit in the woods, the pope is a catholic, ect ect.

    Persuading the kids is another matter of course.

  • by HungryHobo (1314109) on Tuesday August 28, 2012 @08:21AM (#41147603)

    Those who started after the age of 18 did not have the same IQ decline.

    "It's such a special study that I'm fairly confident that cannabis is safe for over-18 brains, but risky for under-18 brains."
    -King's College professor Terrie Moffitt.

  • by Anonymous Coward on Tuesday August 28, 2012 @08:26AM (#41147665)

    Yeah, well, that's just, like, your opinion, man.

  • Passed every exam at school with flying colours and had my first experience of failing an exam at university.

    Of course that could also be explained by going into an exam hung over and sleep deprived. It's hard to say.

  • by Shirgall (110235) on Tuesday August 28, 2012 @08:33AM (#41147773) Homepage

    Breaking the law on a regular basis with a decent chance of being caught and treated harshly by the system probably correlates with a low IQ too, doesn't it?

    • by v1 (525388)

      needs more 'correlationisnotcausation" tagging methinks.

      if A and B appear together (correlation) it doesn't mean A causes B, or even that B causes A. It just means that the two tend to occur together for some possibly very indirect reason.

      I think in this case pot doesn't cause stupidity, but that generally speaking, stupider people tend to do more drugs. Nothing surprising nor valuable to hear about that.

  • by slashmydots (2189826) on Tuesday August 28, 2012 @08:52AM (#41148033)
    But what about all the alleged positive effects like eating a whole bunch and becoming a lazy fast ass and getting arrested...oh wait...
  • by gallondr00nk (868673) on Tuesday August 28, 2012 @08:56AM (#41148081)

    IQ tests are incredibly subjective anyway, and have innate cultural biases. Essentially all an IQ test calculates is how good you are at the test. It has very little to do with "intelligence", however loosely defined.

    • Even if this is true, and the tests are bad, your conclusion is entirely counterproductive to the point of the test. If the tests are bad, the IQ scores would go up the more you take the tests, because you'd know the tests, but Potheads IQ's went DOWN when they took the tests repeatedly over their teen years. So in a way even if the tests are bad, it only understates the problem that Pot has on teenage brains.
  • by mug funky (910186) on Tuesday August 28, 2012 @09:27AM (#41148601)

    correlation does not imply.. um...

    wait, wait...

  • by swb (14022) on Tuesday August 28, 2012 @11:35AM (#41150733)

    As far as I'm concerned, this study really doesn't matter -- even if it *is* right from a methodology and execution perspective, which I'm kind of questioning based on my reading of the news article about it where the only comments were from the Partnership for a Drug Free America, and the fact that it involves self-reporting from surveys.

    Regardless, at a gut level, it seems risky to *encourage* teens to use mind-altering drugs, be it pot, booze or Adderall (it's funny, we never hear these people want to run studies showing the risk of putting developing brains on anti-depressants or stimulants).

    But all of this seems to miss the point -- it seems like people opposed to marijuana legalization point to studies like this with a "SEE!!! IT"S BAD FOR YOU!" attitude, as if the only result that would rationalize legalization is the impossible one (for pot or anything else), where chronic, daily smoking of pot results in nothing more serious than an urge to drink more water.

    This won't happen, and it's tiresome to see these kinds of studies used as some kind of justification for continuing a criminal justice empire costing billions of dollars a year that undermines the constitutional rights of everyone that has utterly failed to accomplish its goal.

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