Heavy marijuana use shrinks brain parts

By Heretic.Ape. · Jun 5, 2008 · ·
  1. Heretic.Ape.
    Heavy marijuana use shrinks brain parts - study

    By Will Dunham

    WASHINGTON, June 2 (Reuters) - Long-term heavy use of marijuana may cause two important brain structures to shrink, Australian researchers said on Monday.

    Brain scans showed the hippocampus and amygdala were smaller in men who were heavy marijuana users compared to nonusers, the researchers said. The men had smoked at least five marijuana cigarettes daily for on average 20 years.

    The hippocampus regulates memory and emotion, while the amygdala plays a critical role in fear and aggression.

    The study, published in the American Medical Association's journal Archives of General Psychiatry, also found the heavy cannabis users earned lower scores than the nonusers in a verbal learning task -- trying to recall a list of 15 words.

    The marijuana users were more likely to exhibit mild signs of psychotic disorders, but not enough to be formally diagnosed with any such disorder, the researchers said.

    "These findings challenge the widespread perception of cannabis as having limited or no harmful effects on (the) brain and behavior," said Murat Yucel of ORYGEN Research Centre and the University of Melbourne, who led the study.

    "Like with most things, some people will experience greater problems associated with cannabis use than others," Yucel said in an e-mail. "Our findings suggest that everyone is vulnerable to potential changes in the brain, some memory problems and psychiatric symptoms if they use heavily enough and for long enough."

    Among the 15 heavy marijuana users in the study, the hippocampus volume was 12 percent less and the amygdala volume was 7 percent less than in 16 men who were not marijuana users, the researchers said.

    The researchers acknowledged that the study did not prove it was the marijuana and not some other factor that triggered these brain differences. But Yucel said the findings certainly suggested marijuana was the cause.


    While about half of the marijuana users reported experiencing some form of paranoia and social withdrawal, only one of the nonusers reported such symptoms, Yucel said.

    The heavy marijuana users, average age 40, said they had used other illicit drugs less than 10 times, the researchers said.

    A U.S. group supporting legal sales and regulation of marijuana took issue with the findings, particularly because they were based on men who were such heavy, long-term users.

    "These were people who were essentially stoned all day every day for 20 years," Marijuana Policy Project spokesman Bruce Mirken said by e-mail. "This study says nothing about moderate or occasional users, who are the vast majority -- and the (study) even acknowledges this."

    "The documented damage caused by comparably heavy use of alcohol or tobacco is just off-the-charts more serious, and you don't need high-tech scans to find it," Mirken added.

    Yucel said the researchers have begun new research on the effects of both short-term and long-term and moderate and heavy use of marijuana. (Editing by Maggie Fox)


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  1. Greenport
    That doesn't mean anything. People who have been smoking marijuana heavily for 20 years have a smaller hippocampus and amygdala...does that state that this has any kind of severe, major impact on the person?

    At worst it says that 20 years of heavy pot use (7 to 10 bowls a day, or 5 joints a day) can make us feel more scared, aggressive, less social, and have a harder time memorizing things. That's not saying much for those who only use it occasionally.

    Of course smoking 5 marijuana cigarettes a day for 20 years will do SOMETHING, and personally I think that proves the effects of pot use are rather minimal.

    What would 20 years of cocaine abuse do to you? Prolly some pretty fucked up stuff. Alcohol? Would destroy your kidneys and liver. Cigarettes? Destroy your lungs and give you cancer. Food? Make you obese and put you at risk of heart attack and other diseases...

    Pot? Oh well you have to write reminders to yourself to do stuff. That's why we invented the pocket book :) And as far as feeling more scared, emotional, aggressive, or antisocial -- not only are there ways to combat all three, but they're just states of mind. Not to mention most stoners I know are LESS aggressive, and while they may be less social regarding people they don't know as well, they likely form very tight bonds with those who they do know well and that's all that really matters.

    And that's after 20 years of smoking 5 joints a day. Are these people still pot smokers? I would like to see a study done where the people quit smoking pot for a year after 20 years of smoking like that -- How much do you guys want to bet that those antisocial/emotional problems start to wane anyways?

    Again, this one says nothing. It's another hypocritical media scare tactic designed to frighten people away from drugs, and again, does a bad job of it. just look at the title -- it's designed to catch your attention. Marijuana use shrinking brain parts sounds bad -- but in all actuality, as the article clarifies (but not to those who don't analyze it correctly) this shrinkage is not a major problem.

    Even with those potential hazards of heavy use of pot over a long period of time -- about 1/4 of somebody's lifetime, the benefits still outweigh the risks.

    There isn't an accurate article out there that can state what physical harm pot use does to a person -- shrinking of brain parts has to account for something major, not just some (likely reversible) decreased memory problems and emotional issues. If it meant that 20 years of pot smoking would cause us to become retarded then that's different. But it doesn't - because pot doesn't make us retarded (at least not for more than about 4 hours.) It just doesn't, end of story.

    If you want to know what pot does to you, just look at the people in the world who do smoke pot versus those who don't. And note how much they're doing and for how long, too.

    They are so desperate that they are scanning people's brains to FIND the problems with it. You don't have to scan a meth-head's brain to figure out what problems it causes, or a heroin addict's brain, or an alcoholic's. I think the entire article thus, is yet again a very poor argument on the dangers of marijuana use.

    20 years of using any drug is going to cause changes in the way the brain functions, it's called adaptation - and your brain is simply adapting to the use of a substance in daily life. It's not necessarily even a bad thing.

    Final thought: Propagandous
  2. Nature Boy
    "While about half of the marijuana users reported experiencing some form of paranoia and social withdrawal, only one of the nonusers reported such symptoms, Yucel said."

    Of course prohibition has a lot to do with this. Cannabis is an illegal drug, possession of which can result in serious trouble. Users become isolated due to the non-acceptance of it in public. I'm sure bathtub moonshine drinkers of the US alcohol prohibition era felt similar at times.
  3. Heretic.Ape.
    ^ word to ya muthafukin mutha my friend.
  4. crackcityrocker
    why even do the study if youre only going to use 31 people?
  5. Paracelsus
    To get preliminary, but still statistically significant, results. Studies with small samples always precede large studies. It saves a lot of money to test your hypothesis on a small sample (to see if there is some merit to it) before starting to recruit subjects en masse.

    This seems to indicate that heavy long-term use does affect brain structure and has minimal effects. But it also shows how low the comparative danger is (imagine how the brain of a 20-year heavy drinker looks).
  6. Politicalchalk
    SwiCCR, 31 people is a good "starting point" as far as clinical studies go. This affords future potential studies to have a starting point, both academically and in terms of funding.

    I have to admit, I laughed when reading this. 5 joints a day for 20 years? Geez. Swim's cat was involved in, well, I believe their term was a "Commucratic Republic" which endorsed heavy pot smoking, as a teen. No one in that group was able to keep up with the upkeep though. It sounds like these people did nothing for the past 20 years except smoke pot, or at least that's how the press report makes it sound.

    One recalls theories of intellectual capacity in the turn-of-the-century 1900s...the idea that each part of the brain is carved out for a specific purpose, ie: "This area is for math, this is music, if this part's big it means you excel at reading but not language" etc etc. This lead to a now-discredited idea that having a larger brain necessarily means intellectual superiority. It gave rise to easy abuses such as another chip in the log of racism, extreme nationalism, and so on.

    "Since people in country A are generally smaller than people in country B, people in B must have bigger brains, ergo, people in B must be smarter than A."
  7. Heretic.Ape.
    Paper has been added to the archives here.
  8. Lobsang
    SWIM does not know why people are suprised at this. It is not so improbable. Would you not expect that chronic daily use of a mind altering drug would not alter the brain? In the brain when you change the inputs the structural neurology can change. So it is said the structure yields function. But in the brain function also can change structure. So SWIM does not find this suprising at all. SWIM means as advanced thinkers we must accept the fact that the "religion" that marijauna can do no harm may be a dogma. SWIM means, what does one expect from smoking 5 joints a day for 20 years....A Nobel prize in advanced physics? :eek:

    (And SWIM is not passing judgement because SWIM did much worse than that)
  9. aerozeppelin123
    Every time a study is posted about cannabis possibly having negative effects, there is always a torrent of people saying it's 'propaganda' or 'scare tactics'. Why is it so difficult to understand that it just might not be a completely harmless and benign drug?
  10. Lobsang
    Well there can be a number of reasons. One of which is that historically the anti-drug camp has said things about drugs like pot that users know are not true. For example SWIM many many years ago in high school was shown movies in Health class that tried to convince SWIMMERS that cannibis would make you think you turned into a werewolf and totally flip and trip out. Well SWIMMERS in the class knew that this was not true and the were usually stoned in class while laughing at the movie. This lead to a lack of trust about cannibis and all drugs. This was stsrted many years ago.

    Also people always defend what they like to do. Like the tobacco smoker that says "Well my grandpa lived to 98 years old and HE smoked 3 packs a day".
  11. crackcityrocker
    amen. i have a hard time accepting the conclusions that alot of marijuana studies come to because of this. given, this one isnt so far fetched. a huge amount of weed being consumed for a period of 20 years is obviously not going to be good for you and will have some kind of detrimental effects (just like most other things). but sometimes my bias gets the best of me.
  12. Paracelsus
    Please don't let this thread (like so many others) degenerate into another ones of those arguments about totally unrelated health aspects of marijuana use. Lung damage, lung cancer, and psychological addiction are not related to the topic.
  13. Shampoo
    Many interesting points have been made in this thread, though they are mostly, if not all, more appropriate for another thread. Please refrain from further derailing this thread. I have requested that many of these posts be moved here: http://www.drugs-forum.com/forum/s...ad.php?t=36672 . Discussion regarding the general harm/lack-therof of cannabis should be focused in that thread, not this one.

    The effects of cannabinoids on LTP in the hippocampus are relatively new to quality research studies looking at neurodegeneration or inhibition of neural growth tissues, and conclusions like that above are likely, but perhaps premature. There are a few threads floating around out there regarding the relationship between hippocampal LTP and cannabinoids, just use the search engine.
  14. Heretic.Ape.
    this discussion has been moved as per above request
  15. Alfa
    Heavy Pot Use May Shrink the Brain

    [IMGL=white]http://www.drugs-forum.com/forum/attachment.php?attachmentid=4983&d=1213866692[/IMGL] Many people believe that marijuana is relatively harmless and should be legalized. There are just as many who believe that its use is the start of all addictions and can only lead to self destruction. The attitude of both sides of the controversy probably has as much to do with personal morals and religious beliefs as with medical truth.

    Reports suggest that long-term marijuana use is associated with adverse health consequences, but there have been relatively few studies that can confirm any disease directly associated with marijuana use. Researchers admit that excess use of almost any substance can contribute to disease and poor health in an individual. A substance that affects the brain and nerves will have more effect with increased usage.

    New evidence indicates that long term heavy use of marijuana can cause abnormalities in the brain. These abnormalities are actual brain injuries leading to memory loss, difficulty in learning, paranoia, delusions and bizarre social behaviors. The new evidence was the result of research by the ORYGEN Research Centre and the Neuropsychiatry Centre at the University Of Melbourne, Australia. Lead researcher Murat Yucel, says the new evidence plays an important role in understanding the effects of marijuana and its impact on brain functioning. Yucel said. "The study is the first to show that long-term cannabis use can adversely affect all users, not just those in the high risk categories such as the young or those susceptible to mental illness, as previously thought,"

    The research team did high resolution MRIs on 15 men who smoked more than five joints a day for more than 10 years. The scans were compared with those of 16 men who did not use marijuana. All of the men took verbal memory tests and had examinations for psychiatric disorders. According to Yucel the more marijuana was used the more the individuals were likely to have reduced brain size in the parts of the brain that control emotion, memory, fear and aggression. Heavy users were also much more likely to develop psychotic disorders. According to Yucel the study challenges the perception that cannabis has limited or no harmful effects on the brain and behavior. The study does not link modest use to neurotoxic effects, only heavy daily use. The study group was not frequent users of other illicit drugs.

    This study is not likely to end the controversy surrounding marijuana use. The researchers said that the study did not prove whether it was the marijuana or other factors that triggered the brain differences, even though it suggested that the marijuana use was the cause. The size of the hippocampus and the amygdale, the two portions of the brain that were studied may have been smaller in the study individuals to begin with and may have contributed to the heavy usage. Meanwhile in May scientists at New York University tested a group of 17- to 30-year-old cannibis smokers who used the drug twice a week for a year. There was no difference between the users and a group of non-users.

    Supporters of legal sales of marijuana did not believe the study was very useful because it covered a very small group of individuals who were long term heavy users of marijuana, and the majority of users are moderate occasional users. The heavy use of alcohol and tobacco is far more serious than recreational use of marijuana according to a spokesman.

    rom a parent's point of view the important question is whether the brain differences were the result of the long term usage, or the age at which they began using the drug. Scott Swartzwelder, professor of psychiatry and behavioral sciences at Duke University, whose research focuses on substance abuse and the adolescent brain, said that it is too early for parents to conclude that pot deteriorates the brain. The study used a very limited set of data, the study was tiny, and looked for extreme behavior. "I'm not sure how relevant it is to the general public." says Swartzwelder.

    The researchers noted that the size of the group is an issue, but finding subjects who used a lot of pot but didn't do other drugs, or have medical or psychological issues was difficult. The continuing use of cannabis within the general population demands a clear scientifically correct study that both sides of the usage controversy can accept.
  16. corvardus
    What annoys SWIM is that scientific papers and reporting of said papers in mainstream media always does the reader a disservice. It would be so much better to have balanced reporting stating....

    Chance of Disabling Disease after 20 years heavy use
    (numbers pulled out of my Green Cheeked Conures' ass)

    Smoking 1:1000
    Cannabis 1:10000000
    Swinging from your pubic hair from a tree: 1:100
    Sex 1:500000
    Flying: 1:500000

    People could then make a better decision on whether the data and the risk being presented to them are in the realms of Higgs-Bosonally miniscule/Slight/Moderate/High/OMG-I'm-so-HIGH/You're DOOMED!

    Is this too much to ask for? :laugh:
  17. Graduisic
    i'd like to see the study side by side with people who got drunk every day for 20 years
  18. wednesday
    heavy pot use
    heavy drinking
    heavy cigarette smoking
    20 years
    what is worse

    wednesday added 3 Minutes and 31 Seconds later...

  19. Bajeda
    I wouldn't.

    We already know that getting wasted every day for 20 years will mess you up badly.

    I'd rather learn more about the long term consequences of cannabis and whether there are harmful aspects one should take note of. For instance, what this new research means.

    The research itself isn't threatening, just the conclusions some people run away with because of it. The whole cannabis vs. alcohol negative effects debate is pretty pointless in this context, they are studying the brain of cannabis smokers.
  20. purplehaze
    These articles are always so incomplete.

    Everytime I see an article like this there is never a full detail description on the subjects.

    I wanna know what they ate, what they drank, how they exercised, other stuff is important to me when conducting these studies that always seems to just not matter when its being reported.

    I'm not being pro marijuana when I say this, nor biased at all for that opinion, but before I will believe anything from a news article, I need to know for sure.

    The best scientist in the world, and a couple of my friends to verify whats up. Seriously though, how can you just automatically assume anything is true without a full analysis, pictures, brain scans, weight documenting, blood pressure, calorie intake, diet, other activitys besides marijuana like cigarettes, alcohol, candy, etc.

    Even the good things about marijuana unless in a PDF file they never say much other than, marijuana slows tumors. % this found in % region. Theres much more to take into consideration, and if we truly wish to progess with the logical method. Investigate, learn, we need to take absolutely everything into consideration.

    Its like Newton said for every action there is an equal and opposite reaction, but how using a play on words, are we sure our feedback is coming from the intended source?
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