Casual marijuana use may damage your brain
April 16th, 2014
09:02 AM ET

Casual marijuana use may damage your brain

If you thought smoking a joint occasionally was OK, a new study released Tuesday suggests you might want to reconsider.

The study, published in the Journal of Neuroscience, is the first to link casual marijuana use to major changes in the brain. And according to the researchers, the degree of abnormalities is based on the number of joints you smoke in a week.

Using different types of neuroimaging, researchers examined the brains of 40 young adults between the ages of 18 and 25 who were enrolled in Boston-area colleges. Twenty of them smoked marijuana at least once a week. The other 20 did not use pot at all.

The marijuana smokers were asked to track their cannabis use for 90 days. All were given high-resolution MRIs, and users and non-users' results were compared.

Researchers examined regions of the brain involved in emotional processing, motivation and reward, called the nucleus accumbens and the amygdala.  They analyzed volume, shape and density of grey matter - where most cells in brain tissue are located.

"I think the findings that there are observable differences in brain structure with marijuana even in these young adult recreational users indicate that there are significant effects of marijuana on the brain," says Dr. Jodi Gilman, lead author and a researcher in the Massachusetts General Center for Addiction Medicine. "Those differences were exposure-dependent, meaning those who used more marijuana had greater abnormalities."

More than a third of the group - seven of the 20 - only used pot recreationally once or twice a week. The median use was six joints a week, but there were four people who said they smoked more than 20 joints a week. None of the users reported any problems with school, work, legal issues, parents or relationships, according to Dr. Hans Breiter, co-senior author of the study and a professor of psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine.

"There's a general idea out there that casual use of marijuana does not lead to bad effects, so we started out to investigate that very directly," Breiter said. "This research with the other studies we have done have led me to be extremely concerned about the effects of marijuana in adolescents and young adults and to consider that we may need to be very careful about legalization policies and possibly consider how to prevent anyone under age 25 to 30 from using marijuana at all."

Researchers have long been concerned about the effects of marijuana on the developing brain - teens and adolescents under the age of 25. Preliminary research has shown that early onset smokers are slower at tasks, have lower IQs later in life and even have a higher risk of stroke.

Dr. Staci Gruber, director of the Cognitive and Clinical Neuroimaging Core at McLean Hospital in Boston and a professor of psychiatry at Harvard Medical School, has conducted numerous studies on marijuana use and brain function.

"This data certainly confirms what others have reported with regard to changes in brain structure," she said. "When we consider the findings of the Gilman ... study with our own and other investigations of marijuana use, it's clear that further investigation is warranted, specifically for individuals in emerging adulthood, as exposure during a period of developmental vulnerability may result in neurophysiologic changes which may have long-term implications."

Gruber says we need to take a closer look at all pot users whether they smoke once or twice a week or four or time times a week.

And she had this advice for adolescents: "Don't do it early–prior to age 16. That's what our data suggests, that regular use of marijuana prior to age 16 is associated with greater difficulty of tasks requiring judgment, planning and inhibitory function as well as changes in brain function and white matter microstructure relative to those who start later."

According to the National Survey on Drug Use and Health, in 2012 nearly 19 million Americans used marijuana. It's the most-used illegal drug in the country and use is increasing among teenagers and young adults.

Results of the new study match those of animal studies, authors say, showing that when rats are given tetrahydrocannabinol, or THC - the ingredient in marijuana the gets you high - their brains rewire and new connections are formed.

Gilman thinks when people start to become addicted to substances, their brains form these new connections too.

"The next important thing to investigate is how these structural abnormalities relate to functional outcomes," she said. "Currently we don't know how much marijuana is safe and I think this study shows that we should be cautious about marijuana use in adolescents and young adults whose developing brain may be even more susceptible to cannabis-induced changes."

soundoff (961 Responses)
  1. Pat

    I love theoretical conclusions like this:

    "Preliminary research has shown that early onset smokers are slower at tasks, have lower IQs later in life and even have a higher risk of stroke."

    Yes, so does consuming two cans of coke a day, not adding an active routine in your schedule, consuming over the counter drugs, and several other reasons.
    Studies like this are so biased and not conducted properly. I am a welder by trade, which involves high precision, attention to detail and completing tasks on time and quickly, it also involves reading and interpenetrating blueprints and detailed drawings that would look like to any random off the street gibberish and another language. I smoke pot, I drink alcohol, but I also live a active lifestyle, and I have zero problems performing my tasks at work. I've also been doing this since I was 19. And, to make it more clear most of the guys I work with do the same as me. They get their jobs done, on time and with quality. It's all about moderation, of course if someone gets completely baked everyday, or drunk everyday, yes it will have a negative effect, but casual smoking and drinking isn't a problem for a healthy human performance.

    April 16, 2014 at 16:49 | Report abuse | Reply
    • mikeVa

      Pat makes a very good point. The massive amounts of sugar consumed today have had much more of an impact than alcohol or marijuana use. Endocrine related illness is one of the top diagnosis in the United States.

      April 16, 2014 at 17:25 | Report abuse |
    • Tea Pot Party

      US Patent # 6,630,507 -- "Cannabinoids as Neuroprotectants" the Federal Gov't holds the patent.

      April 16, 2014 at 17:46 | Report abuse |
    • Craig

      Actually, the study says exactly the opposite: casual smoking of marijuana damages the brain.

      April 16, 2014 at 18:55 | Report abuse |
    • jarrett

      dont trust cnn i could link to a few old news episodes that were later found to be totally faked... i hate how they jump on anything they can to discredit medical use. what they don't tell you is that alcohol causes many changes in the brain too...so does changing your daily habits. the brain is doing exactly what it evolved to do..adapt to changes in its environment both external and internal. i think many user know their brain is adapting to the thc its dont take a scientific experiment to relise this. after so much cannabis use its psychoactive effects no longer are effective. changes in brain structure would make sense why this is happening right? but the study also claims not of the participants had any life issues not legal not academic ext... so why are we worried that the brain is creating new connections in response to its psychoactive effects? this is good because medical users can use it without their driveing ability ext.. being impaired. yet they function just normally still and it still helps them with their pain/cancer ext.. most drugs will cause the brain to rewire but the difference is when you stop taking that drug it takes a long time for the brain to rewire its self again till the point you can actually function again! and umm alcohol dosent just rewire the brain it actually kills cells. Thats something mmj wont do in fact has been found to promote neuron growth. This article is written in a way that it is not a lie but misleads the uninformed.

      April 16, 2014 at 18:58 | Report abuse |
    • Sandy

      I agree.

      April 16, 2014 at 21:12 | Report abuse |
    • Ricardo from Brazil

      I was a heavy user of pot, and I can assume this studies are right. Pot made me get slower and took out my iniciative, and made me a little anti social. For what I can feel, this happens becouse the THC makes me focus in things that are not priority in life, and teaches to be more lazy. It feels very good to be high on pot, but I think that we might reconsider doing this if we want to be in our best mental level, and let pot for 30+ ages (or even more, like 50+), when everything gets more boring. Maybe pot for old people could be healthy for the brain, but for young is no good. Thanks for attention.

      April 16, 2014 at 21:53 | Report abuse |
  2. Hey EVERYONE!!!

    There's a DORITOS coupon!!!

    April 16, 2014 at 16:53 | Report abuse | Reply
  3. Tim

    This is a bunch of bull s. What I got from this article is that no facts it effects you or harm u, but it might in the future. I bet this article was funded by the government and the prescription drug producers. What I have to say is don't spend the money to research the reasons weed is bad, but find the strain that will cure diseases. Cure cancer

    April 16, 2014 at 16:58 | Report abuse | Reply
  4. stark82

    "There's a general idea out there that casual use of marijuana does not lead to bad effects, so we started out to investigate that very directly," Breiter said. "This research with the other studies we have done have led me to be extremely concerned about the effects of marijuana in adolescents and young adults and to consider that we may need to be very careful about legalization policies and possibly consider how to prevent anyone under age 25 to 30 from using marijuana at all."

    Face palm. They... just... don't get it, do they?

    The legalization debate is not about whether smoking pot is good for you. It is obvious that any psychoactive drug including marijuana will have some negative health effects and if so, people should be warned about these negative health effects as in the case of cigarettes. What the legalization debate is really about whether adults should have the right to use and possess this substance without fear of imprisonment or other criminal sanction. Alcohol and tobacco both have much worse health effects than marijuana but instead of banning them for people's "own good" we make people aware of the negative health consequences associated with using these substances and leave the decision up to them. In order words, when it comes to alcohol and tobacco we treat adults like adults but when it comes to pot we treat adults like children. If a warning label has to be stamped on pot as in the case of cigarettes then fine, I'm sure the pro-legalization crowd can live with it as a fair compromise.

    Secondly no one is advocating that minors should legally be permitted to use pot and if you think that the only thing preventing them from doing so you is the fact that marijuana is illegal then you're living in a fantasy world. It is easier for teens to get a hold of pot than it is for them to get a hold of alcohol so clearly there is no correlation between legality and availability to minors.

    April 16, 2014 at 17:00 | Report abuse | Reply
    • craigisanidiot

      Craig your a fuc#ing idiot.

      April 16, 2014 at 18:33 | Report abuse |
    • maestro

      Availability to minors will increase after legalization. Duh.

      April 16, 2014 at 22:16 | Report abuse |
    • K2 baba

      On point brother

      April 16, 2014 at 22:18 | Report abuse |
    • The sheltered Kid

      craig he's 100% correct back in high school i was won of those giodie goodie kids but dispute that, i still knew several dealers in my school (which is one of the top 200 in the nation and in an upper middle class to upper class area). Even now if i really wanted to all i would have to do is make a few calls to get some pot. However i am in college where is much easer to get ahold of such things but the point is it's VERY easy to get pot and about a 1/5 of the people i know have or do smoke pot.

      Personally i'm going to wait till more data comes out on this and maybe i'll go read the paper to see how good it looks, but for now i remain fairly skeptical.

      April 16, 2014 at 22:48 | Report abuse |
    • The sheltered Kid

      ya, in a quick glance through it i've already seen discrepancies... control group drank half as much alcohol and no comments on how they took this into account. i'm surprised they even allowed them to drink alcohol considering it has an effect on the brain.

      April 16, 2014 at 22:56 | Report abuse |
  5. Stephen Daniel

    CNN is working with project S.A.M. Project SAM has deep pockets and CNN is a business who will gladly promote them for the right price. Hoe much did it cost to get plugged on the Gupta show Patrick Kennedy? Project SAM does not want marijuana legalized because marijuana is not dangerous enough. Project SAM owns or will own many marijuana rehab clinics. Their business model relies on government forcing people into rehab who get caught. If marijuana is legalized the business model will not work because not enough people will enroll voluntarily into rehab for marijuana. If marijuana is half as dangerous as project SAM claims, they would stand to make billions off legalized marijuana addicts but unfortunately it is not. Therefore, they have to rely on the judicial system to force people to go into rehab even though the person most likely does not have a problem. I realized CNN was working with project SAM when I saw the DR. Sanjay Gupta 2nd show where Patrick Kennedy claimed he was for decriminalization but not legalization. The Kennedy's made their billions from the ending of alcohol prohibition by making alcohol. Patrick Kennedy could give a rat's buttonhole about a peoples health. He only cares about playing in the game of monopoly. "Marijuana may cause good health to the brain by stopping cancer, Alzheimer's, dementia and other disease". This statement is true and is backed by statistics, years of scientific study. Do not believe what you read without checking the sources and reading the actual study. Shame on you CNN! It is all about money. CNN should focus on humanity once in a while don't you think?

    April 16, 2014 at 17:02 | Report abuse | Reply
  6. lola blaze

    It says it causes "abnormalities" and "changes" in the brain. Nowhere does it state that the changes or abnormalities are a BAD thing. Every substance that enters your body causes some sort of reactions, positive or negative. This study sounds like it wants people to think it is scary that their brain might change.. but, you know what? Sometimes change is a great thing!

    April 16, 2014 at 17:05 | Report abuse | Reply
    • Oliver

      I wrote a reply just like this one. Then I read yours. I was thinking the exact same thing as I read this article. Here is my comment that I posted if your interested... "So what if it creates changes in the brain. Our minds are extremely complex and change all the time. We learn, we grow, we learn new skills, then at some point we might forget some of those skills. The point is is that our brains are changing rapidly. When it comes to the brain, technically anything could be viewed as an abnormality. No one brain is the same. It's time to start embracing these so-called abnormalities and start declaring them unique aspects of the brain."

      April 16, 2014 at 22:11 | Report abuse |
  7. Tim

    Nothing new in the news something bad. Show something real and up lifting. Cure cancer

    April 16, 2014 at 17:13 | Report abuse | Reply
  8. Jeff

    This "Craig" troll seems like a real A hole

    April 16, 2014 at 17:15 | Report abuse | Reply
    • SanjayGupta

      Actually the weedites seem able to make clear and detailed arguments where poor Craig seems unable to construct a lucid sentence. Get on the weed and say no to twitter Craig.

      April 16, 2014 at 18:24 | Report abuse |
  9. Leslie

    They just keep trying to scare the public now that is so close to being legalized. It's the whole refer madness thing again. I am a long time smoker since the age of 14. I smoke an average of 3 joints per day and don't drink alcohol. I graduated from college with a 4.0 GPA. I've also had brain scans because of migraines caused by the birth control pills I was taking. They found no abnormalities with my brain. I was 28 at the time 14 years after I started smoking weed. My question is did the individuals tested drink alcohol as well? Because we know alcohol causes brain damage. I know people who drink heavily, even when their not drinking will tell me something and ten minutes later tell me the same story again. Why don't they start studying it as a cure for cancer instead of trying to find adverse effects. In Spain they have done studies showing when THC and cannabinoids are put in a petri dish with cancer cells the cancer cells were destroyed. They also are doing studies on lab rats showing the same results without destroying other cells. Also without all the adverse side effects of Chemo.

    April 16, 2014 at 17:23 | Report abuse | Reply
  10. Pablo

    To fudido entao...

    April 16, 2014 at 17:25 | Report abuse | Reply
  11. Liv

    How many of you, whom are saying that there is no evidence supporting the statements and data, actually clicked on the study and read through it. I read through it and the data is accurate, Harvard and other scientists didn't just post this article to be snotty doctors that are biased against marijuana. They are simply providing the facts, if you want to smoke pot, then great for you, but at least now you know the consequences if you do.

    April 16, 2014 at 17:26 | Report abuse | Reply
    • mikeVa

      Alcohol consumptions changes the brain too. They've done the same studies with similar results and alcohol looks to have much more of a performance impact not only on the brain but other organs! Same with sugar, it increase the risk of various diseases.

      April 16, 2014 at 17:36 | Report abuse |
    • Hmmm

      To Mikeva's point. Both the control group and test group drank alcohol during the study however the test group drank twice as much alcohol as the control group... yet no mention or accounting of this anomaly in the study. What. Kind of study was this? There is a significant anomaly involving a mind altering substance, which is not the focus of the study, being consumed during the study, where the test group consumes 100% more of said mind altering substance than the control group consume, yet no mention of this in the results... I'm pretty sure this would get shat on during a peer review.

      April 16, 2014 at 17:57 | Report abuse |
    • The sheltered Kid

      look at the p-values, only one of them is significant (a significant p-value is .05)... For those of you who don't know what that means, it's basically means that your data is worthless for proving anything unless your data is significant, and in the scientific community significant p-values are under .05. I haven't even started reading the paper and i'm already finding significant faults. i think i'm gona ignore this paper and move on.

      April 16, 2014 at 23:07 | Report abuse |
  12. mikeVa

    We can pull out a study on sugar or alcohol. They change the brain, increase risk factors for illness.

    April 16, 2014 at 17:30 | Report abuse | Reply
  13. TrollKiller

    Sounds like Craig himself has a lower IQ than the last 45 stones use I've encountered. Craig, use your high IQ to find your rectum, then pull your skull out. Feel free to insert thumb before returning to mouth.

    April 16, 2014 at 17:33 | Report abuse | Reply
    • John L.

      lol you may be a troll but charming and funny to boot! Unlike that other troll Craig who just comes off as bitter and has nothing better to do than hang out here all day....How do people find the time to troll like that?

      April 16, 2014 at 17:51 | Report abuse |
  14. Hmmm

    I just finished reading the study.
    Both groups drank alcohol however the marajuana test group drank TWICE as much as the non smoker group. The study is bunk... It's the weed melting you brains... Let's just ignore the alcohol consumption anomaly...

    April 16, 2014 at 17:45 | Report abuse | Reply
  15. Chris

    the loser Craig seems to have a lot of time on his hands commenting on everything. He must be an unemployed alcoholic on welfare waiting for his cheque to come in on the 20th so he can get his colt 45 and his 5$ box of wine. With a little meth on the side. Stupid redneck DEA supporter.

    April 16, 2014 at 17:48 | Report abuse | Reply
  16. cacique

    The problem is with "casual" let's go a full all-throttle, pedal to the metal kind of blast..

    April 16, 2014 at 17:50 | Report abuse | Reply
  17. john

    Yeah, we don't want to slow down productivity and consumerism.

    April 16, 2014 at 17:57 | Report abuse | Reply
  18. CR Lacey

    If you would like to read the version withoit the media bias attached, you cand find it at http://www.iflscience.com/health-and-medicine/study-finds-recreational-cannabis-use-associated-abnormalities-brain

    April 16, 2014 at 18:00 | Report abuse | Reply
  19. James

    Regarding comments about differential alcohol consumption between the groups – alcohol use was included as a covariate in the analyses so the results account for differential use.

    April 16, 2014 at 18:16 | Report abuse | Reply
  20. bayrat

    What a load of B.S. Who paid for this "study"? The beer lobby?

    April 16, 2014 at 18:20 | Report abuse | Reply
  21. Eddie


    April 16, 2014 at 18:20 | Report abuse | Reply
    • SanjayGupta

      Eddie dude, you need to get high and quit shouting man.

      April 16, 2014 at 18:31 | Report abuse |
  22. Vicki

    I used to smoke bud (pot) since I was 15 and to be honest when I went high to school I was better at my tests and more involved in class. When there was days I didnt smoke and went to school I had no motivation to do anything. As I got older I smoke here and there but for period of times I stayed with out smoking and when I did I felt more lonely, sad, depressed and did not want to be around crowds. Then when I would get back to smoking on a regular basis I honestly had no worried I didnt feel insecure or anxiety when I left the house. I was more social with people and loved the way I felt then. Now Im much older well 36yrs old I stop smoking bud when I was 32 reason being got to expensive for me. During this time I started out with getting major axieties at work did not want to drive felt anxious about something but not knowing what I was anxious about. Dr's put me on Depression pills, anxiety pills and sleeping pills which here and there I still had anxieties and still got depressed. I stop taking them and started up smoking again felt much better got out, worked enjoyed my life again. Feeling much better in life now. So I think that saying bud is bad at young is so wrong I think depending on the person. Im here Im good and I am still pretty damn smart 🙂

    April 16, 2014 at 18:32 | Report abuse | Reply
    • Jenny

      Vicki- Glad that you found your way back to pot. Your communication skills certainly confirm that chronic use has no effect on cognitive abilities.

      April 16, 2014 at 23:50 | Report abuse |
  23. bs sniffer outer

    And now for the bs of today because more Americans are supporting legalization. I wonder who paid for this study? Hmmm possibly the Tobacco industry..

    April 16, 2014 at 18:35 | Report abuse | Reply
  24. pablo1111

    I smoked pot for many years and it has not given me any drain bamage at all.

    April 16, 2014 at 18:38 | Report abuse | Reply
  25. Name*

    40 people in the study from one college.
    In the northeast. Science is laughing at you.

    April 16, 2014 at 18:39 | Report abuse | Reply
  26. Tobias

    The test group had twice as much alcohol intake as the control group = erroneous results. Alcohol KILLS brain cells and causes other damage in the brain and body. Also, even if there are changes in the brain from pot, there's nothing to indicate they are negative, so why are certain media outlets spinning this erroneous study to try and say that it "damages" the brain? Very irresponsible "reporting" here.

    April 16, 2014 at 18:42 | Report abuse | Reply
    • James

      alcohol use was included as a covariate in the analyses so the results account for differential use.

      April 16, 2014 at 18:44 | Report abuse |
  27. bartonizer

    There's no doubt that consumption of a substance or even the participation in an activity can cause changes to the brain. But what do the changes mean in the overall picture? Are changes always bad or even permanent? And how do other things in life affect the brain? One of the two regions of the brain examined in the study is the amygdala. In this article, the study's author implies that the increased size of the amygdala seen in marijuana users is a negative thing. But in the Boston Globe, Dr. Breiter also remarks that cocaine use shrinks the amygdala. Would he suggest that marijuana users balance themselves with a little coke? Context would be helpful, as would unbiased longitudinal studies that accounted for multiple factors. Researchers making blanket generalizations from a limited, cross-sectional study involving self-reporting subjects seems disingenuous at best. Think I'm alone in my reasoning? Here's what a top medical news service today said about the topic:

    April 16, 2014 at 18:43 | Report abuse | Reply
  28. THH

    I was going to comment, but forget my points and lost all motivation to say it.

    April 16, 2014 at 18:44 | Report abuse | Reply
  29. bayrat

    My mother,god bless her soul,had a favorite expression-If you follow someone around long enough you'll catch them doing something wrong.Same thing here!They've been studying marijuana for 50 years and to justify the millions they get from the federal govt they have to come up with something negative.

    April 16, 2014 at 18:48 | Report abuse | Reply
  30. jebbie

    these are great comments. even the apologists for the government-funded studies, bless their souls. but, ever since the War on Drugs was established, the enforcement community has put a lot of (wasted) time in this and is not about to give up their lucrative crusade against weed. now, do you remember what happened when Nixon declared the War? Mexico killed their cannabis crop and flooded us with cheap and potent heroin – in the first two years, I buried 6 friends from od's. quit being stupid about weed – especially these so-called medical professionals. again, who's lining their pockets?

    April 16, 2014 at 19:29 | Report abuse | Reply
    • Jeff

      We were having heroin issues at my last job, 17 to 20 year olds, sometimes they would nod off after work. I think some of the large Mexican cartels have already started moving into the heroin business. Some places are having 10 people die at a time from adulterated heroin. Pot is so benign in comparison.

      April 16, 2014 at 23:27 | Report abuse |
    • Jeff

      I meant nod off "during" work!..

      April 16, 2014 at 23:28 | Report abuse |
  31. chong

    They are so concerned about the brain which is silly. If they want to stigmatize Marijuana, point out the simple and true fact that God did not design the human lungs to hold in smoke. It does not matter what you are smoking, if you smoke anything, you are damaging your lungs. Now pass the cheese doodles cheech.

    April 16, 2014 at 20:00 | Report abuse | Reply
  32. Jeff

    Debunked here. Sorry CNN. This is the last time you flip-flop on me. Sample size of 40?! Get out of here with that.

    April 16, 2014 at 20:06 | Report abuse | Reply
  33. bonnie perkins

    Ok, now tell us you did the same study on the effects of alcohol and anti depressants. What did you find in those studies? Get off it already! Most of america smokes and its time to shut up and accept it.

    April 16, 2014 at 20:11 | Report abuse | Reply
  34. KIRK

    why dont they just quote refer madness and show you turning into a drug crazed monster STUPID STUPID STUPID
    I AM SICK TO DEATH OF PROPAGANDA of course the young need to stay away when in school it causes short term memory loss and drinking makes your drunk if you cant print truth just shut up

    April 16, 2014 at 20:14 | Report abuse | Reply

    And casual smoking or drinking doesn't damage the brain?


    April 16, 2014 at 20:32 | Report abuse | Reply
  36. Paul Pot

    "is the first to link casual marijuana use"
    Why hasn't this been seen before out of 300 million smokers.
    Remember what Dr Sanjay Gupta said, these articles are manufactured to find negative conclusions and data can be 'interpreted' to draw any conclusion one wants to.

    April 16, 2014 at 20:50 | Report abuse | Reply
  37. Anthony M.

    This CNN article misinterprets the original findings of the study published in the Journal of Neuroscience. At the very least, the media should not be offering readers unfounded value judgments regarding the usage of marijuana without properly considering the scientific context of the terms utilized by the cited study. A proper understanding of scientific terms is especially necessary when the cited study–as opposed to what this journalistic piece implies–does not explicitly establish any form of causation between marijuana use and brain damage, i.e., does not directly link marijuana usage to brain damage. To quote the authors of the study: "The next important thing to investigate is how...structural abnormalities relate to functional outcomes." When dealing with science from an intelligent and informed perspective, we need to take into account what scientists are describing when they make use of such notions as "structural abnormalities." To claim that the notion of "structural abnormalities" equates to "structural damage" involves the marshaling of dangerous and seriously misleading assumptions. As per the usage in the Journal of Neuroscience article, "structural abnormalities" describe a deviation from a particular normative structure–in this case, the normative structures of brain measurements that have been collected over the course of numerous endeavors.

    Let us take a far less hostile approach to the evidence offered by the cited study. The analysis of the brains of marijuana users concludes that dendritic arborization (less formally known as the density of dendritic clusters) is higher in specific neurological regions of marijuana users, and that the density of certain grey matter regions in marijuana users is also higher than those of non-users. Does such an increased density factor mean that the brains of marijuana users are damaged? Not necessarily. Scientists are uncertain of how these structural abnormalities reflect on functional elements such as cognitive processes. In other words, the functional relationships between the causes and effects of increased densities in numerous regions of the marijuana users' brains remains inconclusive. If anything, rather than condemning marijuana as a dangerous drug (as the CNN article does), the authors of this article elucidate a curious conundrum that requires a great deal of further scientific inquiry. Let us ask the question: Why do the brains of marijuana users exhibit greater grey matter densities than those of non-users?

    The course of logic utilized by CNN and others to decry marijuana as inherently damaging is rather absurd. To take a colloquial, counterpoised, and equally naive approach to the issue of grey matter densities in the human brain: Is it not better to have bigger (denser) brains? If so, then the published study shows that marijuana users are more intelligent than non-users, because, indeed, their brains are denser. Do we see the problems with such a misuse of logic?

    CNN should revise their gratuitously polemical articulation of the study's conclusions. I find that the misrepresentation of data is a common issue within non-scientific circles, and this CNN article is an excellent example of how a medical notion (structural abnormalities) can assume a negative role through the naive manipulation of language.


    April 16, 2014 at 20:59 | Report abuse | Reply
    • Jeff

      Good synopsis.. thanks!

      April 16, 2014 at 23:29 | Report abuse |
    • JT

      Thanks, after a morning of reading CNN comments, stumbling across your post has made my day. One thoughtful and well written post has canceled out thousands of trolling polemics.

      April 18, 2014 at 12:53 | Report abuse |
  38. Seth

    I heard the guy who did this study on the radio this morning and he clearly had an agenda saying he wanted to prove that marijuana use was harmful. He said it was a "fable" that casual use was considered not dangerous.

    April 16, 2014 at 21:04 | Report abuse | Reply
  39. BHale

    So many studies in conclusions drawn from this research http://www.medpagetoday.com/Neurology/GeneralNeurology/45290?isalert=1

    April 16, 2014 at 21:31 | Report abuse | Reply
    • BHale

      *Not studies–problems. Was typing too quickly.

      April 16, 2014 at 21:33 | Report abuse |
  40. Michael

    Well dam......Now they tell me, maybe if I had known 40+ years ago....

    April 16, 2014 at 21:47 | Report abuse | Reply
  41. Oliver

    So what if it creates changes in the brain. Our minds are extremely complex and change all the time. We learn, we grow, we learn new skills, then at some point we might forget some of those skills. The point is is that our brains are changing rapidly. When it comes to the brain, technically anything could be viewed as an abnormality. No one brain is the same. It's time to start embracing these so-called abnormalities and start declaring them unique aspects of the brain.

    April 16, 2014 at 22:08 | Report abuse | Reply
  42. redundantredundant

    I smoked non-habit forming marijuana for years.

    April 16, 2014 at 22:15 | Report abuse | Reply
  43. luis

    I've been a pot consumer since the age of 15 years old. Im a business professional with a great income and job. complete it all my studies and haves lived a healthy life. this studies need to be more concrete, accurate and direct. its ok to drink coca-cola which literally harms your body the moment you sip it. its ok to smoke cigarets which slowly kill your lungs. im mean this level of hypocrisy is too much. lets get the facts straight and show the world the miracles of marihuana instead of demonizing it.last time i heard, most of violent crimes, car accidents or tragedies are perpetrate it under the influence of alcohol

    April 16, 2014 at 22:51 | Report abuse | Reply
  44. allenwoll

    This subject, like religion, defies rational discussion. . Verifiable facts count as nothing, whereas opinion is 24-carat, absolutely UN-touchable !

    April 16, 2014 at 22:59 | Report abuse | Reply
  45. are122

    If you are around someone who suffers from paranoia and decides to smoke pot...plan to be well away from them for 1 to 3 months after...or there's a good chance you will suffer for it.

    April 16, 2014 at 23:16 | Report abuse | Reply
  46. Duh!

    So I was, like, isn't this, like, obvilike, ous, or something?

    Whatever. Dudde.

    C'mon. It IS obvious. Stoners turn their focus and motivation skills into soggy sand.

    And, sure, other things people smoke, drink, take, or use can be harmful.

    But it, like, way proves, like, THE POINT when pot advocates make these silly analogies.

    The issue isn't if or what other substances are also harmful. It's "Why lie about a damaging substance–and so needlessly damaging yourself?"

    April 16, 2014 at 23:18 | Report abuse | Reply
  47. bg

    There are only two substances that can kill you from withdrawals. One you can buy anywhere. The other is the fastest growing prescription. Alcohol and benzo's. But let's focus on the ones that may kill a couple brain cells. And if your house catches on fire, focus on cleaning your dishes...

    April 16, 2014 at 23:28 | Report abuse | Reply
  48. Jimmy Limo

    Of COURSE pot changes your brain ! THAT'S why people SMOKE it ! Is your brain DEPRESSED ? Smoke some... Do you have PTSD ? Smoking will help... Have epilepsy ? Pot can DEFINITELY help... Suffer from ALCOHOLISM (which can KILL you... or someone else) ? Non-toxic and non-addictive pot will make you healthier and help you live longer...Having trouble sleeping ? Suffering from pain ? Eating disorder ? Much (if not MOST) of what we suffer is IN OUR HEAD... in our brain ! In a society that takes a pill for this and a drink for that, we CHANGE our BRAINS ALL THE TIME ! Pot is just a natural and organic way to do it safer... So WHAT'S THE PROBLEM ? Sensationalist BS headlines from a study no doubt funded by Big Pharma and corporations that profit $$$ from the status quo... LEGALIZE NOW, AMERICA !

    April 16, 2014 at 23:55 | Report abuse | Reply
  49. Blarg

    This study shows a correlation between cannabis and altered brain morphology. They didn't study whether is affects cognition or not. The sample size was pretty small too.

    April 16, 2014 at 23:56 | Report abuse | Reply
  50. Muju Naeem

    So does this mean that Dr. Sunjay Gupta is officially changing his mind about Marijuana use? Previously he was pushing for legalization as well "because it was safe".

    As a smoker myself, and a reader of CNN, I am very curious to know his official position on this.

    April 17, 2014 at 00:18 | Report abuse | Reply
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