Study: Young Adults’ Casual Marijuana Use Causes Brain Changes

(prensa420/Flickr)

(prensa420/Flickr)

A new study by Boston researchers is believed to be the first that shows that young adults who even occasionally smoke marijuana could be damaging their brains.

The study, just published in The Journal of Neuroscience, found abnormalities in areas of the brain related to emotion, motivation and decision-making.

The researchers say the degree of brain changes appeared to be directly related to how frequently the study’s participants smoked pot.

The authors write in their paper:

The results of this study indicate that in young, recreational marijuana users, structural abnormalities in gray matter density, volume, and shape of the nucleus accumbens and amygdala can be observed. Pending confirmation in other cohorts of marijuana users, the present findings suggest that further study of marijuana effects are needed to help inform discussion about the legalization of marijuana.

The study comes with a plurality of Massachusetts residents supporting the legalization of marijuana for recreational use, and as the state is in the process of opening medical marijuana dispensaries.

Here & Now has more on the study this afternoon.

And hat-tip to The Boston Globe, which has more on the findings.

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  • Cristina4Jesus

    Pot is a damaging, addictive drug, worse than tobacco. The rise of Big Tobacco was nothing compared to what we are seeing now — the rise of Big Marijuana. Lots of addicts, people dying young and it will take decades to remove it from the culture.

    • Edie_VA

      I predict that 25 years from now the millenials who see no harm in marijuana use in society will be blessed with grown children who don’t or won’t leave the parental nest, and expect their parents to keep up a generous allowance for their weed and beer. karma, folks. Until this happens, nothing will convince the “true believers”.

      • guardian

        Truth …… nothing but the truth…. why would any humans say, “We should smoke pot!!”….unbelievable.

  • Stephen Weber

    Scientist Blasts Report Linking Casual Pot Smoking With Brain Abnormalities
    http://www.huffingtonpost.com/2014/04/22/marijuana-brain-study_n_5170422.html
    “The paper is terrible on a number of levels,” Lior Pachter, a computational biologist and professor at the University of California, Berkeley, told The Huffington Post. “It reeks of dishonesty.”

    No, this study doesn’t show marijuana wrecks your brain
    http://www.vox.com/2014/4/17/5621558/study-marijuana-doesnt-wreck-brain

    How Bad Is Marijuana for Your Health? What recent press coverage gets wrong.
    http://www.slate.com/articles/health_and_science/medical_examiner/2014/05/marijuana_brain_studies_comparing_pot_with_alcohol_and_cigarettes_on_health.single.html
    “Reporters overstated the findings, mischaracterized the study, and failed to mention previous research done on pot smoking and health.”
    A press release from the Society for Neuroscience trumpeted the Gilman study’s importance because it looked at casual users rather than regular pot smokers, who form the basis of most marijuana studies. That claim is dubious in the extreme. The subjects averaged 3.83 days of smoking and 11.2 total joints per week. Characterizing these people as casual pot smokers was a great media hook, but it defied common sense.. Just two years ago, for example, Janna Cousijn and colleagues published a study on a group that she called “heavy” marijuana users. In the average week, they smoked 3 grams of cannabis – approximately 2 grams less than Gilman’s casual smokers.

    How a Marijuana Study Can Poke Holes in Your Brain
    http://motherboard.vice.com/read/how-a-marijuana-study-can-poke-holes-in-your-brain
    “The main problems with the study, according to people who have pushed back, is its small sample size (20 college students), its definition of “casual” (the average study participant smoked 11 joints a week), the fact that most of the weed smokers were also drinkers, and the fact that only one MRI scan was done for each participant, which is not ideal.”
    Lior Pachter, a University of California, Berkeley computational biologist, has done what is most likely the most thorough review of the paper, and concluded by calling it “quite possibly the worst paper I’ve read all year.”
    Jacob Sullum wrote a piece for Reason called “Study of Pot Smokers’ Brains Shows that MRIs Cause Bad Science Reporting.” But Sullum also misses the mark a bit. MRIs and studies like this don’t cause bad science reporting; misleading sources cause bad stories. And correlation not equaling causation is a cardinal rule of science – one that was missed here – but so is bad data in, bad data out.

    • guardian

      it still showed abnormalities in the pot smokers….period. There are other studies also….see those too.

  • Driizzy Aiden

    I see a lot of LUNACY is the cannabis user circle.

    You need to see it [cannabis] from a different (scientific) perspective. How can you deny evidence? Some of you are like religious bigots! Totally denying the studies laid before you! Don’t be ignorant.

    I have NOTHING against cannabis users, only ignorance.

  • Driizzy Aiden

    You can NOT compare apples to oranges. Of course alcohol is worse then marijuana. So is bleach. That does not eliminate the potential damage to the brain and psychological effects. I’v smoked weed for years, about two ounces a day. But through personal experience i understand the psychological effects, and then there is this study showing that the neclues accumbens and the amygdala are in fact effected by cannabis.

    I’v stopped smoking weed, and became happier, more motivated, and more creative. My memory and writing improved and so has my art.

    This is just me though, i’m sure you can be a fully functional cannabis smoker. But this is evidence that is does if fact effect the brain, everybody’s brain is different, but don’t be like a religious bigot when it comes to scientific study against a drug.

    Denying the truth doesn’t change it. :p

  • Danny

    I have read the original manuscript and see that this is a PILOT with a weak research design (small number of subjects, historical dependent variables, associations only – no causation, no measures of effect, etc.) and a number of uncontrolled variables (e.g. all the marijuana subjects and none of the control subjects were cigarette smokers). There is missing information such as how the subjects were recruited. It is probably fine work, but, at best, only contributes a speck of evidence to a very complicated field of study. What I am curious about is how the media chooses to publicize scientific studies. There are thousands of studies published every week with both weak and strong research designs on topics of interest to the public. A basic principle of science is that it takes lots of evidence to answer any question definitively. So, it seems irresponsible to me to present such a small window into any question.

    • guardian

      look at all the studies on pub med then Danny…. There is overwhelming evidence that marijuana is damaging major organs including the brain, heart, and lungs. You never, ever, smoke a medication.

  • Neutral

    I wonder how this compares with the studies of concussions and CTE. I.e., it is might be more dangerous for children to play soccer (heading the ball) or football than smoking Marijuana. I.e., there is already convincing proof that multiple concussions or even hit trauma not reaching the level of concussions can produce brain damage.

    So although I think that children including adolescents should not be smoking Marijuana, I think that claiming this study is conclusive of brain damage is going a bit far. But I also wouldn’t let my children head the ball while playing soccer or play football.

    As mentioned in earlier comments it seem like it was a very small sample size and relied on the honesty of the individuals as to what type of user they were.

  • Linda MacDonald

    What came first? The chicken or the egg? This is an interesting study but I think the authors will have to do a longitudinal study to prove their thesis. Do scans on kids before they start smoking marijuana and then do the experiment again with the same group of subjects when they are older.

    • Edie_VA

      Another method: Go to state psychiatric hospitals and closely research the under 30 patients admitted with psychosis. My neighbor’s grandson became a daily marijuana smoker at age 15, had his first psychotic episode when he was 17. He had two more psychotic breaks by age 25. (Accompanied by anger, rage, unreasonableness – his mother called police to take him away). His psychiatrist gave this warning, if you continue, you may go into permanent psychosis. (This kid believed he was an archangel, and called his two uncles daily for his archangel assignment).

      • Linda MacDonald

        Maybe he was trying to quiet the voices when he started smoking pot. He could have been in early psychosis. I don’t believe the pot caused his psychotic breaks. The early adult break is typical for schizophrenia.

  • dust truck

    “Abnormalities” does not equal “damage”. Such a conflation is an unwarranted and irresponsible reading of the data which was drawn from an admittedly small sample population.

    How come your Facebook post still says “Damage?” That’s unnecessarily alarming.

    • guardian

      Damage causes the abnormality “dust truck”…. The structure shows abnormality FROM damage…..jeez…

  • Wayne Hinklin

    They worry about the how the brain is affected when someone uses weed but alcohol is so much worse. Alcohol kills brain cells and they never return. Weed on the other hand doesn’t do the same damage and helps with pain management and is a good anti-inflamitory. The growers breed the plants for specific purposes. They are working on and have been pretty good at growing weed that doesn’t make you into a couch potato. If people were to find out more about what progress has been made in the growing process and cultivation they would understand that it isn’t as bad as the authors of a lot of articles are claiming. I have experienced the use of this and have gotten relief from the use of this hybrid weed. I use it as an anti-inflamatory and it works better than those NSAIDS which cause more health problems and have much worse side effects. Weed doesn’t cause any of the side effects that legal drugs do but the big drug companies pay for studies to make it seem like weed is bad and their drugs are safe. They pay off the FDA reps and sell their drugs legally to people who use them and think they are getting what they need to make them healthy. The side effects are much worse and cause more problems for people but since they are leagal medications they aren’t evaluated as harmful. The big money drug companies get what they want because they have the money to buy whatever they want and pay off the officials that control the drug business in the U.S. They don’t care that their products are harmful because they prepare for any law suits by setting aside money for law suits ahead of time because they know they will make plenty off their drugs to cover them.

    • TJtruthandjustice

      Weed has major side effects related to motivation, executive functioning, mood and memory. It may be useful for a limited number of specific medical conditions. But you are fooling yourself if you think there aren’t side effects.

      • nilanjan bagchi

        That shows that you haven’t smoked weed!! I suggest you to give it a try sometime. Your conception alongwith perception will change.

        • http://www.youtube.com/lswisdom77 LaNita Noah

          cigarette companies are about to get really mad.

        • TJtruthandjustice

          Believe me – I have smoked plenty of weed. Way too much. Over years and years. I’ve seen the damage first-hand. To myself and to people I know. I bought the BS that it was a harmless, non-addictive drug with no negative side effects. Alcohol kills people every day, so to say that it’s “better than booze” isn’t saying much at all. If people can smoke it a few times a week or whatever, fine. You have no problem. But many of the pot smokers I have known kept a steady blood level of THC at all times by smoking several times a day, every day of every week of every year. And if they didn’t have any for a few days, believe me, they’d be jonesing for it hard.

        • Matt

          Seriously, I smoke pot occasionally and your very delusional if you think weed doesn’t cause brain damage. There is a study between people who have never used pot and people who smokes a lot of pot and there is a HUGE difference. Stop smoking and wake up son

          • Breath of Fresh vacuum

            Nevertheless, we should learn here that moderation is the key to using the herb rather than abusing it. Affects, yes. Some highlight the negatives, others high-light the positives. Yes, there are other substances to be used as intoxicants that are worse to the human body, though more legal than marijuana.
            So, Why is the herb not as legal as asprin

        • dtteacher

          Why do you feel the need to smoke weed? What reality are you trying to escape and replace with a drug?

    • Jesse James

      Where did you get your facts? You’re probably high while you write this garbage. Why do you idiots always try to compare alcohol to pot. They’re both bad. What’s going to happen when pot reaches 100% potency? We already know what happens with alcohol because it’s there. I suppose you’re going to tell me that the medical benefits will be increased….. or maybe you’re going to try and justify these morons blowing themselves up as they try to extract the oils using butane. Stop smoking for a month or two so you can think straight or just accept the fact you’re fooling yourself if you think this shit is safe for our children and the future of America.

    • dtteacher

      wayne….there is plenty of damage from smoking pot. I am a medical professional and you NEVER SMOKE A MEDICATION!!! It is so ridiculous, i can’t believe the credulity of the american people who now support this crap. ALL MEDICATIONS WE HAVE COME FROM A PLANT OR ANIMAL SOURCE and we put them in a pill or injectable form. If it works, make it into a medication THAT YOU DON”T SMOKE. This stuff damages brains, lungs, heart and other organs,…check the American Lung ASsociation, or the Mayo clinic website. The mayo clinic website is hilarious because it lists like 45 conditions that you “should be careful if using marijuana” while having the conditions. There is so little thinking going on with this issue, it’s amazing how much americans are sheep and just do whatever the media says is correct.

    • Edie_VA

      How often does alcohol cause psychosis in a 17-yr old?

    • guardian

      You have absolutely no evidence, and there are no studies to support ANY of the benefits you claim for pot. All of the benefits claimed are just pot smokers yelling, “This is great stuff!!!”. It IS addictive, it is damaging to the brain, lungs and heart. A pot smoker is 5 times more likely to have a heart attack within an hour of smoking pot. It has a very long half life in the brain, which causes a slow withdrawal, remaining in the system for over a month, it does alter reaction time, depth perception, short term memory, and is correlated with psychiatric disorders in well done scientific studies. There is no question it is bad for the human body….we will see how bad in the very near future. All the current studies are saying “STOP, don’t legalize marijuana because it’s doing bad stuff to people.” — see the studies for yourself….they all recommend waiting to approve it legally.

      Regardless, the herd will need to be thinned so keep smoking the crap that destroys your body.

  • G.

    An increase in brain density and volume? Sign me up!!!

  • TJtruthandjustice

    Pot is a powerful, addictive drug with negative side effects. Anybody who thinks it isn’t addictive has never lived with or been a serious pothead, or is serious denial. Chronic use negatively impacts motivation, executive functioning and mood. I am so sick and tired of the Pollyanna pro-pot contingent. If you’re getting chemo or have MS or something similarly debilitating, go ahead and smoke it. Otherwise, please shut up and find something more useful to do.

    • Hugo Burnham

      Or shut up and can the “anti-” hyperbole. It is not “addictive”…any more than caffeine or other mild toxicants (which is what they all are), and there are many positive effects.
      No absolutes…but you types can’t stand that, eh?!
      Now – how about some REAL problems to discuss?

      (written as a non-participant, btw…who has lived with, known, worked with, etc. more pot-heads over the years than you can shake a stick at.)

      • Jesse James

        What is wrong with you idiots??? Every time someone suggests a negative side effect you immediately attempt to find another substance that shares the side effect further verifying the truth that recreational marijuana isn’t safe. I know that responding to idiots like you is a waste of time but why cant you just face the fact that marijuana has negative side effects? We all realize that everything in the world probably has some type of negative effect but you don’t see people showing their ignorance making false claims because they cant put the pot down.

        • Hugo Burnham

          Charming reply. And incorrect in determining my intent, or acknowledging my not even having ‘picked the pot up’.

          There is a quite a chasm between acknowledging that there are negative effects (..as with anything ingested, especially intoxicants…) – which I, for one, do – and the spitting, spluttering hyperbole and ‘sky is falling’ wailing of those opposed; especially considering their arguments are so often wrong, poorly researched, and defy reasoned pragmatism. (Talking of “false claims”.)
          Excessive ingestion of ANY substance (yes…including water!) will cause harm.

          Un-bunch for Easter, Jesse. (…but don’t over-do the chocolate!)

    • NoFightingInTheWarRoom

      Still doesn’t explain why alcohol is legal, but marijuana isn’t. Plenty of things that aren’t healthy are legal. Should we ban cheeseburgers? Watching multiple hours of TV? How about cigarettes? Your argument is very flawed.

      • TJtruthandjustice

        I didn’t say it should be illegal. But the pro-pot propaganda is just ridiculous. My kid is in high school and pot is everywhere. I wish I had known about the brain damage it causes in teenagers when I was their age. The research is becoming increasingly clear: It is NOT harmless and has a lasting impact on the brain, even after the person stops smoking. If you can smoke on the weekends and leave it there, cool. Most of the potheads I’ve known don’t do that. People who smoke daily are asking for trouble.

        • dust truck

          Except it’s not “damage.” The study did not use that word. WBUR is just trying to scare weak-minded people like yourself by creating a false headline. (Though it seems like they changed it now.)

          • TJtruthandjustice

            “Structural abnormalities,” AKA damage. Give me a break.

          • dust truck

            No it’s not the same and it’s disingenuous to pretend otherwise. From the study: “the present findings suggest that further study of marijuana effects are needed to help inform discussion about the legalization of marijuana.” Which means that no conclusion about damage was made.

            You… don’t like reading much do you?

          • TJtruthandjustice

            You can wait around for your “proof” and keep smoking all you want. Ten years, twenty years, whatever. Meantime, I’ll go out on a limb and say that “structural abnormalities of the brain” is enough of a red flag to stop doing something, especially if you are younger than 25 and your brain is still developing.

          • TJtruthandjustice

            And here’s another one from July: New research may give backing to parents telling teens to “just say no.” A study in mice from the University of Maryland School of Medicine reveals that regular use of marijuana during adolescence could damage brain function, potentially increasing the risk for schizophrenia and other psychiatric problems … “The striking finding is that, even though the mice were exposed to very low drug doses, and only for a brief period during adolescence, their brain abnormalities persisted into adulthood.” http://www.medicalnewstoday.com/articles/263936.php

          • dust truck

            Lets see here, a study in mice, and again, they identified them as “abnormalities”. Scientists aren’t stupid you know, they won’t use the term damage unless something conclusive about cognition or atrophy can be proven.

          • Darius

            mice study ….. “”The drug is really quite a remarkably safe one for humans, although it is really quite a dangerous one for mice and they should not use it.”
            -J.W.D Henderson Director of the Bureau of Human Drugs, Health and Welfare, Canada” Sec for others studies look at my second comments
            ” The research is becoming increasingly clear: It is NOT harmless and has a lasting impact on the brain” there is not if you want check email to studies author no one will say you that MJ cause brain damage. There is no causation proof.
            http://www.ncbi.nlm.nih.gov/pubmed/21747398
            What is funny all of studies you reference show brain change in difrent part of brain while not in the same. (alcohol studies show alter the same brain regions.)
            for example this study cited here “Study: Young Adults’ Casual Marijuana Use Causes Brain Changes”
            “To verify that volumetric alterations did not merely reflect group differences in global brain volume, we determined that there were no significant differences in ICV, total brain volume, or gray or white matter volume”
            “”Structural abnormalities,” AKA damage. Give me a break” plasticity cause “Structural abnormalities,” you cal this damage? for example taxi drivers have greater brain regions responsible for spatial orientation compared to normal person this is structural abnormalities but they are better in spatial task you call this damage? like you say “Give me a break.”

          • TJtruthandjustice

            Here’s another brain damage study from 2012: “Scientists from MCRI, Melbourne University and Wollongong University compared MRI scans of the brain for 59 people who had been using marijuana for an average of 15 years to 33 healthy people who had never used the drug. After measuring changes to the volume, strength and integrity of white matter in the brains of all participants, researchers found that long-term heavy cannabis users had disruptions in their white matter fibers … The brain’s white matter is responsible for information passed between different areas of grey matter within the nervous system, and unlike grey matter, which are the brain’s thinking areas that peaks at age eight, white matter continues to develop as people age. Seal and his team found that there was more than 80 percent reduction of white matter in the brains of users.” http://www.medicaldaily.com/marijuana-use-causes-brain-damage-confirmed-241869

          • dust truck

            Wow. 59 people. What a huge sample. Those scientists must be proud.

        • dtteacher

          Absolute truth you are throwing TJtruthandjustice…. This stuff is brain altering. I have done dissections of human brains that were marijuana users and it’s scary how much fewer folds are in their brains…showing neuron death. You don’t need a lot of brain cells to stare at a wall and eat potato chips.

  • foghamar

    We will have plenty of subjects nationally to follow to determine if this is an actual issue.

    That being said, the potheads I knew in the past didn’t use it for anything other than to get high and stay that way. They got loaded the minute they got up and stayed that way until they passed out that night. It was more important that their wives or their children and came before paying for food or rent.

    We’ll just have to wait for 20 years or so and see what happens societally and clinically regarding brain abnormalities as well as lives helped from the occassional use of pot.

    We’ll also have a chance to see how many people are endangered by driving while loaded and how many animals and children are poisoned by it because people who use it are too loaded to realize it can be dangerous to kids and critters.

    I suspect we’ll continue to legalize it and deal with whatever the repercussions and benefits may be. (shrugs)

    • David Meyer

      And, of course, you can’t think of ANY people who drink that way … first thing in the morning through last thing at night, more important than wife(?) or kids(?) or paying for food or rent?
      In my college years, pot was “recreational”, not the “habitual” you describe. Students might miss class with a hangover, but not because of pot. My question to you is: are you sure the drug being abused, in your experience, was pot? How?

      • foghamar

        I lived in a small town in Idaho where I provided social services. When I say small, I mean a town where you don’t need a phone because everyone knows everyone else’s business. I knew these folks far better than I wanted to.

        The guys (they were all guys) bragged about how they were so stoned for so long they couldn’t function if they weren’t stoned. Pot came before anything like feeding the kids or paying the rent. Realize, I was enmeshed in this little town, so I knew the wives, the kids, the parents, the grandparents. I was one of the people the families came to to get things like help with food, medicine, rent, etc. because most of the money in the family was going up in smoke – literally

        I knew who sniffed paint, who sniffed glue, who huffed brake fluid, who preferred to booze it up, etc. Then there were the ones who did everything they could lay their hands on – but they didn’t live all that long, generally. There were also the opiate addicts. And the Moms who brewed pot tea to keep the kids loaded so the little ones didn’t bother them. We took those kids into custody because giving toddlers and grade school kids sweetened pot tea is really lousy parenting.

        Of course there are maintenance drunks who drink all the time. And we know what that sort of abuse does to the body and the brain.

        Now we are legalizing pot and we’ve got a good 20 years to go before we find out just how much it affects the brain, etc. We’re doing the experiment letting the members of the public who want to use it be the guinea pigs.

        People have been using it illicitly for a long time. Now fewer people will go to jail – which is good. And we’ll have more volunteers smoking it to see if it really screws with the brain like the scientists in this study think it will. Since I’m not a scientist doing this study I don’t know what they’ll find.

        Personally, driving under the influence of pot is as dangerous as being loaded on any other drug so I’m all for throwing the book at anyone under the voluntary influence of drugs who goes driving or boating.

        • David Meyer

          So … you CAN think of at least a few people who use other drugs – like alcohol – that way. Good to know.

          The people you talk about, they have problems. The drugs may be the LEAST of their problems! They are not “addicted” to marijuana, they are addicted to escaping their crappy lives. I’d say they do not provide a useful example of the marijuana experience. I’ve known people who smoked a couple of joints a week and you’d never notice, half a day later. And they never, that I’m aware of, did something aggressive or angry while using. Stupid? Sure. I’ve also known folks who never touched a drug who did similarly stupid things and people who did likewise stupid things and blamed their religion.

          I would ask that you base your conclusions on a less self-destructive sample. If your sample is looking for relief from massive problems – even if they have come to cause those problems themselves – your results are likely to be skewed. Like, why are you blaming their bad results on pot, when they also abused “paint, who sniffed glue, who huffed brake fluid, who preferred to booze it up”? And that was before you got to the opiates!

          Note that I am NOT saying “pot is harmless”. Compared to alcohol or opiates? Sure. But, that’s a low bar, don’t you agree? We need good studies, not the lies the government pasted together 40 years ago.

  • http://www.drugpossessionlaws.com/ Drug Possession Laws

    This is a pretty small sample, so it will need additional study. Certainly any physiological changes to the brain are of concern.

    There needs to be a serious study of the significant BENEFITS of medical cannabis, as well as the potential risks.

    No one should be afraid of the truth.

  • JBK007

    can’t decide to like or delete this, oh never mind, sniff….