Marijuana’s Impact On Brain Function “Minimal,” New Study Says

[Editor’s note: This post is excerpted from this week’s forthcoming NORML weekly media advisory. To have NORML’s media advisories delivered straight to your in-box, sign up for NORML’s free e-zine here.] The consumption of cannabis, even long-term, has a “minimal” impact on brain function, according to a systematic literature review just published online by the journal Psychological Medicine.
An international team of investigators from the United Kingdom, Spain, Brazil, Australia, and Switzerland conducted a systematic review of the effects of cannabis on brain structure and function.
Authors wrote, “We reviewed literature reporting neuroimaging studies of chronic or acute cannabis use published up until January 2009. … Sixty-six studies were identified, of which 41 met the inclusion criteria. Thirty-three were functional (SPECT/PET/fMRI) and eight structural (volumetric/DTI) imaging studies. … Only three of the structural imaging studies found differences between users and controls.”
Investigators concluded, “Minimal evidence of major effects of cannabis on brain structure has been reported,” noting that marijuana users and controls perform similarly on cognitive tasks.
According to a 2001 study published in the journal Archives of General Psychiatry, long-term cannabis smokers who abstained from pot for one week “showed virtually no significant differences from control subjects (those who had smoked marijuana less than 50 times in their lives) on a battery of 10 neuropsychological tests.” Investigators added, “Former heavy users, who had consumed little or no cannabis in the three months before testing, [also] showed no significant differences from control subjects on any of these tests on any of the testing days.”

0 thoughts

  1. It doesn’t matter what effect Marijuana has on cognitive ability, health, or tax income. Keeping it illegal benefits the prison lobby enormously. Incarceration is profitable, scalable, and a damn strong growth industry. We build new prisons, and train prison guards, it’s great for the local economy. It’s more profitable to arrest Marijuana smokers and put them in prison than tax a dime bag at the local green apothecary. As long as there are draconian laws for us to enforce, and politicians we can lean on for our cause, You smoke pot, you are getting incarcerated. You think that just because we have more people in prisons than anywhere else in the world that we don’t want more? Do you think we only have control over people within our razor wire walls and cages? Have a problem with that? If you speak up too much, we can guarantee that your stay with us will be your final destination.

  2. To Rick Seymour:
    Ummm…do you understand how science works? Comparing high and non-high groups is the only way to have a valid study.
    It’s a concept from somewhere around 7th grade science, a control group.

  3. “Minimal evidence of major effects of cannabis on brain structure has been reported,” noting that marijuana users and controls perform similarly on cognitive tasks.
    After reading the article, I have made my own conclusion that marijuana obviously does effect the brain, because the comment above makes no sense at all.
    I have personal issues with cannabis as my 15 year old son, is becoming increasingly more reliant on the stuff. I have contacted the police, ask FRANK, social services and no one wants to help me, many of you have made maverick comments about the use of cannabis and that it should be legalised etc etc, but I can tell you that from personal experience, it effects your personal status, drive, enthusiasm, attitude.
    Those of you who are Pro-cannabis are exactly the idiotic peers that my son is aspiring to be.

  4. #49 AGJ Says:
    July 29th, 2009 at 6:32 pm
    I would take your complaint one step further:
    I would love to see public health care rationed
    to the point where the uninsured are only provided
    the barest of essential services.
    I would love to see an America where citizens are
    held accountable and responsible for the choices they make.
    That said, it is my body and I will do with it what I please.
    The issue here is that the policy in place for the control
    of substances is both unconstitutional and egregiously
    dim-witted. Studies (such as the topic of this posting)
    showing scientifically what we all already know to be
    true ought to be the basis for policy, not propaganda
    stemming from racist, greedy businessmen from the 1930s.
    RE: AGJ,
    – Which complaint are you referring to???
    — If it was the ones about public-health-care and those
    who are over-burdeneing it with their
    “lavish, self-indulgent lifestyle”,
    that was #42 Kasado, making general asumptions about
    everyone here, (on NORML-blog),
    “heart clogged, lung diseased, artery hardened,
    high cholesteraled, tumor riddled” lives.
    – The uninsured are ALREADY only provided
    “the barest of essential services”,
    unless it’s for some immediate, life-threatening emergency,
    then you still have to wait, and wait and wait…
    – I know how to live a healthy life, of which,
    America’s health-care system
    plays VERY LITTLE role in maintaining it…
    – It actually comes down to SYNTHETIC vs. NATURAL, (both medicine and food).
    The UNhealthier, synthetic, compromised options are less expensive, yet, are more
    agressively-promoted, even mandated, over healthier, natural ones,
    (that’s what I hate about this world! ).
    – Why should only “YUPPIFIED” flower-children
    be able to afford to eat healther organic-foods,
    drive more-reliable, fuel-efficient vehicles,
    live in more energy-efficient houses?
    – Why should heart-healthy, plant-based oils, be drastically more expensive,
    (such as olive), or even suppressed / illegal, (such as hemp),
    while heart-clogging, hydrogenated-oils are still widely-used?
    (Only showing as zero trans-fats on food-packaging,
    (via tricky, truncated-math),
    whereas the actual numbers,
    (to the Right-Hand Side of decimal-point),
    are still significant, albeit, hidden).
    – Why should healthier plant-seed based drinks,
    such as soy and hemp milk be 2 to 4 times MORE expensive
    than unhealthy, sickening, bovine-lactations? (dairy-cow milk).
    – Why should more effective, natural-medicines, nutritional-support and non-invasive
    medical-procedures be more expensive, downplayed or even suppressed / criminalized?
    (Ever notice that the majority of so-called “illegal-drugs” are of natural origin, yet,
    ONLY the less-unhealthy plant-sources, themselves, are unavailable / truly-suppressed?).
    – – – – –
    to #42 Kasado’s list of of disease-conditions:
    Heart clogged, artery hardened, high cholesterol?
    PLANT-BASED oils,
    (Including hempseed-oil).
    Plant-based OILS neither contain, nor raise cholesterol,
    UNLIKE animal-FATS…
    A certain percentage of cholesterol is actually NECESSARY…
    in limited amounts…
    for nerve-fiber-insulation and vitamin D production…).
    Lung disease?
    INEXPENSIVE VAPORIZERS for ALL who would ordinarilly smoke…
    (Not fertilized with radioactive, polonium-bearing phosphates),
    ADDITIVE-FREE herbs,
    Not containing flavor-enhancer chemicals, (i.e. cigarette-tobacco);
    Nor contaminants, (i.e. gas-tank-flavored, Mexi-Schwag brickweed…).
    – The only role which the FDA ought to have concerning herbs is
    is ensuring product-quality and truthful-labelling, nothing more…
    – No ‘schedules’ against naturally-occurring plants;
    Only apply such towards synthetic-compounds and
    chemically-modified plant-derivatives…
    Tumor riddled?
    Antioxidant Phytocompounds,
    including all naturally-derived cannabinoids,
    not just THC…

    Cannabinoids PROMOTE NEUROGENESIS, and vice-versa…

  5. I smoked pot and it cause me a depersonalization. Pot in high doses isnt so safe as people say it is. It makes you depressed,depersonalized and it causes anxiety.
    If someone wants to talk about depersonalization and weed please add me to msn its

  6. The statements that Pot affects everyone differently, as does alcohol. however alcohol has lasting physical affects on the body. This study is showing there that there is no lasting effects

  7. Eat, drink, and be merry. Just take the responsibility when you become ill and don’t ask society for a healthcare bailout.

  8. Vaporizers are great, but seldom used. Lack of portability.
    No one will ever convince me that a life time of breathing ultra hot smoke into ones lungs is healthy for you. Whether tobacco, marijuana or even sage.

  9. Someone send this to the US Drug Czar. That guys a totally ignorant douche. It boggles the mind that weed is still illegal, and some people(who almost definitely have never used) think that’s right. This is good news though

  10. 54 jayliggitt
    If your son is 15, he’s, by nature, rebellious. The more you say don’t, the more he will say do. That’s the nature of the beast. You could allow him to speak, while you listen. By the way…if you’re going to lecture him…be sure you know what you’re talking about, because he simply won’t listen to anymore misinformation, or misinformed parents, or
    authorities. Just my opinion…and…perhaps one you will reject…but…if it helps…well…so much the better.

  11. This is good but old news to people who have been smokers for years like I have. I saw the coolest movie called “Super High Me” which basically illustrates this point short term but first hand. Check it out, it’s good. I am now unfortunately currently on probation for a driving offence and get tested monthly, so I don’t smoke anymore, but I’m sure I’ll get back into it in a few months when I’m off probation. However, unfortunately, legalizing it is just going to be the first step in the battle, and while obviously, and important one, not the whole battle. The next phase is one I am also currently involved in, and that’s job searching. As I said, I don’t smoke now, so I have no problems with this right now, but it is hard to find a job these days that doesn’t drug test and not hire when you piss dirty for Marijuana, which I think is total bullshit. And I have a feeling that won’t change with most of the jobs just because it becomes legal to use, hopefully I’m wrong. I mean I know there are all these ‘cleasers’ and whatnot out on the market these days, but it always seems a crap shoot. I have had one work, and one fail. And the point is, whether or not I smoke pot on my own time should have nothing to do with whether or not you hire me, and this study just reiterats that point….

  12. I just happened to notice that those in favor of marijuana usage, which I assume to be marijuana users, have terrible grammar, lousy spelling, and don’t seem especially coherent. I think the “studies” are junk science, probably designed by marijuana users.

  13. #61 Kasado Says:
    July 30th, 2009 at 10:34 am
    Vaporizers are great, but seldom used. Lack of portability…
    RE: Kasado,
    – I strongly-disagree.
    Have you ever heard of,
    are you aware of the
    VaporGenie vaporizer?
    (VaporGenie is the worlds first vaporizing pipe,
    I don’t work for VaporGenie,
    (NOR am I being compensated by them…),
    I completely agree with their

    SELECTED INFO and TEXT from their website:
    The VaporGenie: The worlds first vaporizing pipe!
    The VaporGenie vaporizer pipe is dramatically safer
    and more pleasant to use than a conventional combustion pipe.
    It vaporizers your herbal blends or tobacco instead of burning them,
    thereby greatly reducing tar and particulate inhalation.
    The VaporGenie vaporizing pipe gently heats your tobacco
    so that it does not burn.
    Tar and toxic smoke are greatly reduced.
    The VaporGenie pipe provides super-smooth vapor.
    There is no coughing or burning throat.
    It feels like you are inhaling warm, flavored air.
    The VaporGenie pipe is used with a lighter and is completely portable.
    You can take the VaporGenie pipe anywhere. It fits in your pocket.
    The VaporGenie pipe is not electronic. It is simple to use and reliable.
    The VaporGenie pipe is guaranteed against product defects for life.
    The VaporGenie pipe is a high-quality,
    durable product that will provide you with
    many years of satisfying vaporization.

    Cannabinoids PROMOTE NEUROGENESIS, and vice-versa!!!

  14. #69 Justin Says:
    July 30th, 2009 at 4:37 pm
    “I just happened to notice that those in favor of marijuana usage,
    which I assume to be marijuana users, have terrible grammar,
    lousy spelling, and don’t seem especially coherent…”
    RE: Justin,
    – It’s not just marijuana-users, those in favor of marijuana-usage,
    who have poor-grammar, atrocious-spelling…ad-infinitum…
    – It’s America in general;
    Stoners, drunks and the so-called “drug-free”.
    – The American public-educational-system is far
    more to blame.
    – We’re a third-world nation, intelligence-wise,
    compared to Japan and certain, selected European-countries…
    Very sad, INDEED!!!

    Cannabinoids PROMOTE NEUROGENESIS, and vice-versa!!!
    BBCode is the GATEWAY to HTML, Javascript and Klingon…
    (NOTE: This comment-post was HAND-CODED,
    without use of web-dev “helper-applications”).

  15. 69 Justin
    You obviously have an external disorder of a internal manifistation.

  16. #72 Rebel with a cause
    What’s a maniFISTation??? 😆
    Did you mean to type “maniFESTation???”

    Cannabinoids PROMOTE NEUROGENESIS, and vice-versa!!!
    BBCode is the GATEWAY to HTML, Javascript and Klingon…
    (NOTE: This comment-post was HAND-CODED,
    without use of web-dev “helper-applications”).

  17. HogWash Bull…Marijuana makes people lazy, creates mood swings, and creates an urge for other drugs. I have seen it with my own eyes, also Marijuana makes the girls undress quickly for fornication and adultery.
    Save the lies for the comic central or the comedy channel, clown researcher probably was smoking weed during their research.
    Weed Kills!

  18. 73 Neurogenesis1:29
    You’re correct…I meant “fest.” But…”FIST” must be on my mind.

  19. #74 Anthony P. Says:
    July 31st, 2009 at 8:04 am
    HogWash Bull…
    Marijuana makes people lazy,
    creates mood swings, and creates an urge for other drugs.
    I have seen it with my own eyes,
    also Marijuana makes the girls undress quickly for fornication and adultery.
    Save the lies for the comic central or the comedy channel,
    clown researcher probably was smoking weed during their research.
    Weed Kills!
    RE: Anthony,
    Are you effin’ joking?!?
    (vocal-inflections of sarcasm
    don’t translate well to print / text,
    so I assume you’re NOT joking),
    No laffin’ matter, ashwype!!!
    – Cannabis has varied effects upon individuals,
    depending upon specific-ratios of THC to cannabidiol,
    and the particular individual, as well.
    (Some people are “lazier”,
    more disfunctional WITHOUT IT!!!).
    – The lack, (rather than presence of), cannabis creates
    the urge for other, more dangerous substitutes.
    (INCLUDING ALCOHOL, as well as crack, meth and opiates),
    make the girls, (women), undress far more quickly than pot!
    – Alcohol / strong-drink, is always the specific disinhibitor mentioned
    (for purpose of more easily-enabling fornication / adultry),
    in Scripture…
    Not to be extrapolated to milder relaxants…
    – Please, learn the truth about cannabis,
    or else, may you die at the hands of,
    as a result of, alcohol / drunks!!!
    Initial, deliberate orthographical-erratum,
    courtesy of Miss Spelling Intentional. 😉
    Cannabinoids PROMOTE NEUROGENESIS, and vice-versa!!!
    BBCode is the GATEWAY to HTML, Javascript and Klingon…

    (This comment-post was HAND-CODED,
    without use of web-dev “helper-applications”).

  20. #76 Kasado Says:
    July 31st, 2009 at 9:10 am
    No way am I paying $55 for a pipe
    – Neither am I, Kasado.
    – If I had the extra $55,
    I would,
    (for this specific design),

  21. #75 Rebel with a cause Says:
    July 31st, 2009 at 8:42 am
    73 Neurogenesis1:29
    You’re correct…I meant “fest.”
    But…”FIST” must be on my mind.
    RE: That’s what I figured, Rebel…

  22. 74 Anthony P
    You say…”I have seen it with my own two eyes.”
    What two eyes? Did you have your glasses on? Did you see it with eyes that couldn’t see…or…hear it with ears that couldn’t hear? You’re certainly talking with a mouth that has no meaning.

  23. BULLSHIT!!!!! Smoking cannabis makes you MUCH cleverer. This article could even be misconstrued to imply that the difference was the other way round. (By non-smokers).

  24. Ah 74)”Marijuana makes the girls undress quickly for fornication and adultery.”
    Well what the hell is wrong with that? Are you gay or hate sex? God wants us to have sex you know…
    Alcohol really is better for getting chicks in bed you know. Pot really doesn’t work that well for that but if you think its “bad” well what can I say? You would rather people go to jail for a harmless plant? Ugh!

  25. well, as a 30 year pot smoker. I know that there is a definate differance between the thirty yrs i smoked pot and the now as of Nov. 5th / 2009. 6 yrs i have NOT done any drugs other than perscribed by a Dr. and I always hated pills (still do). there is a definate improvement in my memory functions !!! I used to look for things I had in my hand for hours and couldn’t find. (untill I looked in my hand) would lay something down and Never find it again. put things up so they would NOT get lost. (and never see them again) and now this dosen’t happen to me any more? so you decide whats the differance? I’m not against smoking a lil pot but anyone that somkes pot (that will admit the truth) will tell you that the same things happen to them all the time. I dont think that hurts you but it does affect your short term memory alot. that is where they should spend their government grant money so they can fix the short term memory problem and then legalize it for all to enjoy !!! OH but they can’t do that because they make too much money off of those court cost, fines, legal fee’s, and puttin people in jail for something that was here when we came to this OVER TAXED, OVER POLICED, OVER RULING, FREEDOM LOSING, RIGHTS REMOVING, COUNTRY WE CALL The United States Of America. DAMN I THOUGHT WE LEFT A PLACE JUST LIKE THAT TO START A FREE COUNTRY

  26. Hey America, wake up!!!! Marijuana is the least harmful drug out there, certainly better than any of those nasty prescription drugs that doctors hand out right and left leaving those who take this crap feeling worse than they did before they took them. There are no side effects from marijuana as compared to the chemical based drugs which has many.marijuana should be legalized, it’s a natural herb put here by God for crying out loud. I trust God before I trust any pharmaceutical company or doctor. The United States Gov’t. needs to wake up.

  27. wow, science finally proves what the public already knows. Give it 10-15 years, and I bet the government will prove it with their studies!

  28. #42 what the fuck is public financing to pay ones medical bills ? I dont think you have the slightest idea what you,re yappin about! Oh you mean welfare ? Nationalized death care? Fuck you and your high horse I,ve been in the health care industry for years and have never seen anyone w/mj caused hardening of the arterys ,and have never seen anyone that has (fallen apart) due to mj consumption ! Id gladly sign a waver cause you can take my place in line @ the local VA where I get sub standard care for my service connected disability ! No one here is intrested in abusing their bodys Thats why we choose mj over BIG PHARMYS poison !From your mean spirited post its obvious you are probably suffering from some mental disorder ! so fuck off! And you too #74 Moron ! !!! weed never killed anything ! the only dope arround here is you !

  29. P.S. to post 80
    74 Anthony P. I tried with everything in me to forget what you said…”Weed Kills.” The only thing that kills is your post…”IT KILLS ME WITH LAUGHTER.” Please, make some more posts…I need a good laugh today. HA! HA! HA! In your face.
    Forgive me Lord…Anthony has a right to his opinion…
    he just needs a blessing.

  30. steveyboy
    Who really knows what causes disease or any other other malady? You say that mj never causes any of them. How do you know? Does anyone ask about past drug use of their patience during examinations? And if they do, why would anyone risk loss of health insurance, employment, or even their freedom by telling the truth?
    Sorry, but your shrill, irrational, hateful ranting does nothing for the cause of legalization.
    Oh also, I don’t want to pay for your medical bill when you have a brain aneurism due to your crazy blustering.

  31. Hey krassado ,I dont have all the answers like you , but all you have to do is open your eyes to the side effects of these pharacecuticals ,they’re worse than the (cure ) I have seen the devastating effects from rushing these drugs to market ! And again from my own experience, has had very little adverse side effects ! How many of these (mainstream drugs ) have been recalled ? too many to list here ! If mj has no medicinal value then why do the pharma companys try to make synthetic versions of this god given herb? For the money ! In God I trust ! not this government , not big pharma , not pola-trick-sters ! And dont worry about paying my medical bills , I dont ask for anybodys help in any way ! Hows that for blustering?

  32. Hey Krassada P:S Please dont try to tweek the conversation by mis-quoting posts , I dont believe I every said the phrase (NEVER CAUSES ) I said, I’ve never seen ! So lets be specific ! Shall we ?

  33. 88 Kasado
    There are now something like 17,000 studies on cannabis. What does it take to get it in your thick skul…17,001. I don’t think any of us are going to get through to you. You have a closed mind…and
    …that’s your WALL. You really don’t seem to be an advocate…but…you are entitled to you opinion…as ridiculous as it is. I don’t mean to insult you…but
    …open your mind and let some fresh air in.

  34. All this ranker over a call for responsiblity for ones actions. I love it! Maybe it will force some to drop their Cheetos, stop watching brain numbing TV, get off their couchs and fight for their freedoms.

  35. #81 Rebel with a cause Says:
    August 1st, 2009 at 7:57 am
    74 Anthony P
    You say…”I have seen it with my own two eyes.”
    RE: Rebel,
    Sad to say, it sounds like Anthony’s
    THIRD-EYE is atrophied and / or calcified…


  36. 93 Kasado
    Now your talkin’…and…now I’m listening..and…
    you’re absolutely right. We must take responsibility for the results of our actions. If we don’t…we become the beast…trying to defeat the beast.

  37. 94 Neurogenesis1:29
    RE: 94 your post…93 Kasado…95 my reply.
    I don’t know yet. I think he’s got the picture.
    At first I thought he had occulo-colanitis…you know…when your eyeball gets attached to your asshole…and you get a shitty outlook on life.
    We’ll see.

  38. 94 Neurogenesis
    First…I meant 74 Anthony P.
    Second…I mean colonitis…with an “O.”
    Third…I’m not clicking on any cylinders this morning. Too much information to process this a.m.

  39. Its not just the “government” who wants to keep it criminalized, its the police, the lawyers, even areas like agriculture, drug and clothing industries benefit from the prohibition of marijuana.
    Its against their best interest because they either get funding from the government to enforce pot laws, or are benefiting as pot could run their products out of business.
    heres a great video why pot should be decriminalized, and goes into what i talked about above.

  40. the government is bullshit completely they are simply faces to the power the power is big bis. pharma…, insur…, tobbaco, oil, and even the milk industry. these companies are running our country we have lost our rights and freedoms and they have wiped their ass with the constitution so many have fought and died to build and protect now what are going to do about it play games talk shit and hope they make laws to our wants well keep trying i wish itd work they wont money talks and we dont have the money so why would they listen even if all us pot heads pulled our monthly stash money to put into a congressman’s pockets it still would be enough these people or i should say coperations control theser people and will continue to do so as long as we continue on the current path we are on only way we will ever change anything is for the mass to stand up and say no more and take back our country fuck the goverment long live the consitution

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