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NORML Responds To Latest ‘Pot Shrinks The Brain’ Fears


marijuana creativity brainNORML’s Deputy Director today on Alternet.org addressed new media claims that cannabis use can potentially shrink the brain:

[excerpt]A new study identifying minor differences in the brain imaging of habitual marijuana consumers compared to non-users may be ideal for stimulating sensational headlines (e.g., “Regular pot smokers have shrunken brains, study says,” Los Angeles Times, November 10), but tells us little in regard to whether pot poses actual health risks.

Specifically, an MRI scan revealed less gray matter in the orbital frontal cortex of pot-smoking subjects compared to those who had never used the drug. Researchers also identified increased connectivity between certain regions of the brain in regular marijuana users compared with non-users.

So precisely what do these findings tell us in regard to pot use and health? Not much. Since the study design is not longitudinal, investigators cannot determine whether these differences are caused by subject’s cannabis use, whether these differences existed prior to subjects’ ever trying cannabis, or whether these differences persist when users’ cannabis consumption ceases.

Most importantly, investigators in this study failed to determine whether any of these differences are positively associated with any measurable adverse performance outcomes, such as cognitive performance or quality of life. It may be that these cannabis users are functioning in their daily lives in a manner that is indistinguishable from controls, in which case the imaging differences may hold little if any real-world significance. (In fact, one of the paper’s authors acknowledged, “[C]hronic users appear to be doing fine.”)

Full text of NORML’s response, “Media Leaping to Extremely Faulty Conclusions from Study on the Effects of Marijuana on the Brain,” appears online here.

Source: NORML - make a donation


About Author

Johnny Green


  1. That is ironic that you say You don’t win people over on an issue by insulting them, you have to figure out a way to connect with them” but in your previous post you streotyped all cannabis users as irrational.

    As far as the study, anyone that reads about it will conclude it was poorly done, and the original objective of the study was probably something different than what they came up with. i also find it odd to be done at UNM and UT of all places, let alone it was two different universities.

    we know about as much about grey matter as we do about alien life. what we do know is there is other evidence out there linking psychological benefit for certain functions regarding reduced grey matter. we also know on a base level neurogenesis is very good. we also know cannabis decreases inflammation throughout the body and perhaps the brain. And we know that cognitive effects were tested in this study as well with pen and paper tests, and there was no difference in that aspect.

    To me, this seems like a “counter point story”, something that came out and journalists ran with but has little credibility.

  2. Right. And you can’t persuade bigots who, because of the monstrous enabling of the fraudulent prohibition, propaganda, and demonization, have found in marijuana consumers, the perfect, state-approved scapegoats.
    Nothing can feed their hate like that, and they are loathe to give it up.

    You can only expose them, shame them, and force them back under their rocks.

  3. Captain Obvious on

    A larger brain means nothing if it is in bad health. In an inflamed brain, the anti-inflammatory effects of cannabis are much wanted. I would imagine that may come in handy if cranial pressure needs to safely be relieved too.

    Perhaps the synthetic medication and other diseases are inflaming the so called ‘healthy’ brains and the cannabis is providing anti-inflamatory/neuroprotection like so many other studies have shown?
    “Researchers also identified increased connectivity between certain regions of the brain in regular marijuana users compared with non-users.”
    “[C]hronic users appear to be doing fine.”

  4. Chess-masters, in one study, had shrinkage of gray matter, compared to non-players, suggesting evidence of increased brain efficiency.

  5. If not straight from the NIDA, then from the same source they get their funding, the ONDCP. A very large portion of their $25 billion annual budget is parceled out to fund research like this. That’s a lot of scratch to go around to pay for shoddy science.

    And I do mean shoddy — I went back to see if this paper referenced the infamous “Cannabis lowers IQ” study (Meier et al.) that has been so widely debunked. They didn’t! In fact, when they discuss the (non) results of their attempt to find correlative mediating/moderating factors in the OFC network that would predict IQ, they did not reference *ANY* paper purporting a correlation between low IQ and cannabis use — there was no citation, at all. It is, quite literally, and unsubstantiated assumption they were testing. They should have put 2+2 together when they didn’t find anything.

    Academically speaking, they pulled “cannabis lowers IQ” out of their ass, and then proceeded to test their unsupported assertion! I can’t believe any neuroscientist worth his/her salt would believe they took an accurate sampling for IQ — the way they recruited subjects was through fliers and advertisements offering financial compensation. Smarter people usually have good jobs and are not as willing to sell their time to be a research subject. Put simply, you’re not going to get an accurate sampling for intelligence if you only bring in people who need cash. Fact is, with that setup, and a fair distribution of the fliers, you’d expect the average IQ to be below 100. 100 is *the* average IQ, with equal halves of the population falling on either side of that number. Everyone with an IQ above 100 has, by definition, above-average IQ. That’s how IQ is supposedly calculated.

    I wonder if they *DID* reference that debunked paper, but removed the reference. You see, the same journal that published THIS paper is the same journal that published Meier et al. in the autumn 2012 edition, and also published the debunking of Meier et al. in the spring 2013 edition: The Proceedings of the National Academy of Sciences. Publishing the Meier paper with a blatant confound was an embarrassment for PNAS. Now, they’ve published something else that never should have made it passed a reviewer.

    Frankly, I’m seriously starting to question the validity of the peer review process at PNAS, if this is the 2nd paper in as many years that was politically motivated. I mean, the physiological differences are very interesting when examined in an ONDCP-free vacuum. It’s very interesting that the punishment/reward center of the brain is significantly more highly connected in cannabis users, while the specific part of the OFC network that emotionally evaluates punishment is SMALLER in cannabis users.

    Had the researchers done some RELEVANT cognitive measurements on the subjects instead of that ridiculous MPS (which again, their analysis implied cannabis users are happier the *earlier* in life they started smoking), they might have seen specifically how relative size of the punishment center *actually* affects cognition relative to the OFC. What if this shows cannabis users have low anxiety because of stressing rewards/benefits over punishment? Or this research *could have* shown a physiological reason why mass incarceration has not discouraged cannabis use, and never will, had they given their subjects *relevant* tests for the OFC network (not the MPS, not IQ).

    I don’t understand how this POS made it to publication. It’s as if there’s one or two people at PNAS who deliberately allow these awful papers to slip through the review process. And that drop in the IQ deviation when the alcohol users were removed from the cannabis group still bugs me. The interval dropped from plus or minus 12.2 to plus or minus 1.4 — that cannot be by accident or chance. The average IQ of cannabis users who do not use alcohol all fall within less than three points of each other by coincidence? The deviation goes from an interval almost 25 points wide to less than 3 points just by removing the alcohol users, and the mean *drops*? There’s no way!

  6. You can’t persuade or win over the people that make a living off the backs of cannabis users. These are the people that deserve scorn and need to be publicly ridiculed and shamed, over and over…

  7. I don’t oppose it and have never stated that I do, so it would be wise to keep your foul comments to yourself.
    What I am stating is the fact that educating those who aren’t on board with legalization is a much more effective option than dissing them about being uninformed or biased.
    You don’t win people over on an issue by insulting them, you have to figure out a way to connect with them. And the burden of creating an effective connection rests with those attempting to make the connection in order to change a mindset/attitude.

  8. The study’s subjects were heavy users who got stoned 3 times a day for 10 years… Want to see a picture of someone’s brain who got DRUNK 3 times a day for 10 years ?

  9. “The new findings, reported Monday in the journal PNAS, confirm findings about chronic marijuana use from rodents. But scientific evidence in humans has been more mixed” Okay if I’m not mistaken there is a substantial difference between a mouse and a human so WTF does this study have to do with anything.

  10. I like the way you think! I was thinking nearly the same thing. Perhaps the regular users have more connections that provide greater efficiency.

  11. “We should give every credible study a close look”…..yup did that and I guess I’m biased and irrational because I perceive a conclusion which makes assumptions and needs further study. So at this point I’d like to connect with those that oppose it to say: fuck off….No offense intended to the poster but I prefer to NOT keep my enemies closer than my friends.

  12. The brilliant scientist Carl Sagan wrote that his best ideas came to him while stoned in the shower. Scientist. Stoned. Brilliant. Did he smoke much weed in order to get good ideas? Would you?

  13. Blowing off the study is foolish, and failing to identify and comment on the key aspect of the study is also a failure.
    The critical aspect of the study that was conducted at the University of New Mexico is the daily regularity.
    In their study the magical regularity numbers were smoking it three times per day and doing this for a decade or longer.
    Odds are most people haven’t used it multiple times every day for years.
    We should give every credible study a close look to determine the key aspects of their findings and how/why these emerged.
    Otherwise, we’re simply “blowing smoke” and undermining the credibility of the most positive aspects of medicinal use.
    I often hear that marijuana users are biased and irrational, and in many instances this has proven to be accurate.
    Especially until rescheduling and legalization is a reality, every effort should be made to connect with those who oppose it.
    We can’t force anyone to get on board with our use preference, but we can continuously make every effort to communicate the proven medical advantages.

  14. Leonard Hester on

    It is our duty as American citizens to expose propaganda and call bullshit where it exists! Get it legal nation wide!

  15. “Two things are infinite: the universe and human stupidity; and I’m not sure about the the universe.”
    Albert Einstein

  16. Perhaps better connectivity requires less grey matter and the brain is efficiently compensating in that respect. So maybe weed smokers brains have become highly developed to do more with less. I can’t wait for the real research which will show how beneficial this amazing plant is to humans!

  17. http://rt.com/news/204311-usa-cannabis-brain-decrease/

    Under comment section:

    Jillian Galloway: “When marijuana’s been legalized we’ll be able to put warnings like these onto the sides of marijuana packets – something impossible to do today while it’s illegal.”

    Snapple: “They did a study on the brains of master chess players compared to non-players. Chess shrinks the gray matter.”

  18. Makes about as much sense as determining that large people have bigger hands… So obviously their brains are much larger than small boned people… “Why of course I can play a piano, after all, my father was a piano mover!”

  19. Great. Another mischaracterized neuroscience paper… Nobody touting this paper knows boo about the brain…. *sigh*

    Getting science filtered through journalists is usually very flawed and misinterpreted. Thanks to journalists not understanding scientists, there are still idiots out there who believe we only use 10% of our brains. That urban myth was born in the 1960s when a neuroscientist told a journalist that we know how 10% of the brain is used. The journalist flubbed that tidbit in his article horrendously, saying instead that we “only use” 10% of the brain. And thus, tens of thousands of science fiction plot lines were born. This is why it’s so important to go straight to the source.

    Fine. Let’s deal with this.

    This paper did a lot more than compare the sizes of different parts of the brain. They tested the connectivity of different regions, as well. Connectivity between different regions of the brain, it is believed, indicates those regions cooperate cognitively (not a big reach, really). A basic rule of thumb in neuroscience is that “what fires together, wires together” as well as “if you don’t use it, you lose it.” Higher degrees of connectivity implies that part of the brain is doing very, very well — the more “neural pathways” (white matter) are used, the stronger they get. Reduced connectivity implies reduced cooperation. Imaging studies with twins into the link between neural connectivity and IQ show correlations between higher IQ and higher degrees of white matter connectivity (again, not a big reach).

    From the study’s abstract: “The results showed that compared with controls, marijuana users had significantly less bilateral orbitofrontal gyri volume, higher functional connectivity in the orbitofrontal cortex (OFC) network, and higher structural connectivity in tracts that innervate the OFC (forceps minor) as measured by fractional anisotropy (FA).”

    The higher connectivity implies it’s used more frequently. We also know generally what cognitive functionality (memory, perception, language, etc.) has been “positively correlated” to activity in a given region of the brain. The OFC, for example, is generally associated with the emotional evaluation of punishment and rewards. Specifically, the lateral orbitofrontal cortex, the part of the brain we’re talking about in this study, has been associated with the emotional evaluation of punishment.

    So what does this tell us? Nothing, concretely! That’s the frustrating part. Here’s a link to the full paper:


    They had subjects fill out what’s called the MPS (Marijuana Problem Scale), a 19 item survey in which they only have three replies: no problem (0), minor problem (1), major problem (2). Your MPS score is determined by adding up those 19 numbers. Higher scores mean more problems. However, the MPS simply doesn’t appear to be a relevant measurement. Never mind the fact that its name presumes cannabis use causes problems — the fact that it’s just one degree of freedom better than a True/False test makes it almost useless, IMHO. Also, every problem the MPS asks about can be explained by cannabis prohibition (not necessarily the substance, itself): legal problems, financial problems, guilt, lack of self confidence, trouble sleeping, family issues, etc. All this is moot, however, given their findings!!! From the paper:

    “The functional connectivity of the bilateral OFC showed similar patterns where there was an inverse correlation with age of onset of use such that earlier age of onset leads to higher functional connectivity of the bilateral OFC. Finally, there was an inverse correlation between the left temporal lobe functional connectivity and problems related with marijuana use, such that the greater the functional connectivity of the left temporal cortex to bilateral OFC, the lower the total score on MPS.”

    A low score on the MPS would imply a very happy life (if we grant that the MPS is even slightly useful). The earlier in life cannabis use started, the higher the level of connectivity to the OFC. Higher connectivity is correlated with a lower MPS score. More connectivity is therefor associated with a lower MPS — a happier life.

    At best, the results of this paper tell us cannabis users have a higher degree of connectivity associated with the part of the brain responsible for the emotional evaluation of punishment (after 80 years of prohibition — go figure). Higher connectivity between the OFC and the left temporal lobe associated with cannabis were correlated with a happier life on the “Marijuana Problem Scale.” In the end, the researchers found absolutely no correlation between the reduced volume and any behavior measurement they used, *INCLUDING* intelligence quotient. That’s right — having a tiny bilateral orbitofrontal gyri has absolutely no correlation to lowered IQ when you properly consider the other factors that have been PROVEN to affect adult IQ scores, like alcohol use. From the paper:

    “Lastly, to partially address how these abnormalities are related to cognitive processes, we conducted a mediation analysis to assess whether neural abnormalities (OFC gray matter volumes, OFC/temporal lobe functional connectivity, FA/RD of forceps minor) mediate lower scores on IQ in marijuana users. We did not find that the causal variable (i.e., marijuana use) was significantly correlated with the mediator variable (i.e., OFC gray matter volume, OFC/temporal functional connectivity, and FA/RD of forceps minor) and outcome variable (i.e., IQ).”

    Overall, the paper *did* have a prohibitionist vibe to it — they were hunting for negative effects caused by cannabis from the outset. The use of the MPS is proof enough of that, but the tone of the paper is also meant to please whoever at the ONDCP funded it. They presuppose the causal link between lower IQ and cannabis use — they simply wanted to see if the ONDCP’s favorite unicorn is mediated by the parts of the brain found to be different between the control group and the cannabis group (lo and behold, the unicorn is not apparently frolicking through our OFC).

    At least they were semi-honest about the “other factors” that could account for lower IQ in their cannabis group — little things they didn’t account for, like “environmental and/or genetic factors” like, I don’t know, maybe a criminal record they got from a possession charge that landed them in a less-than intellectually engaging profession. It also bothers me that they say they removed all alcohol users from the cannabis group to do the IQ analysis, but they NEVER give the adjusted mean IQ score for the for the control group after (if?) the alcohol users were removed. In the scientific community, that’s what you might call a hole in their analysis big enough to drive a truck through. It’s a vitally important comparison to make, especially when you consider studies have implied cannabis use repairs damage done to the brain by chronic alcoholism.

    When you remove the alcohol users from the cannabis group, the average IQ changes from 105.8 ± 12.2 to 104.0 ± 1.4. Look at the change in the deviation — it drops from ± 12.2 to ± 1.4…. What accounts for that huge change? This is where the raw data would be invaluable.

  20. maybe bad weed does take it away
    but good weed brings it back
    takin it takin it takin away
    bringin it bringin it bringin it back lol

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