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. anonymous

    It's definitely stupid to say that no changes in the brain occur. I think many smokers realize there are harmful effects, but by admitting to them they are throwing the chance of legalization out the window.
    When dealing with drugs that alter the chemistry of your brain it just seems logical that some structures might change to cope.(Lets not forget that some legal prescriptions like antidepressants would probably do the same thing since they work in a similar fashion.)(Even Alcohol, or certain types of thinking can change brain structure)
    We need to do more research on if these changes are bad though.
    As far as we know these changes and changing connections are for the better for some, or have hardly anything to do at all.

    Personally the thoughts i've had while under the influence of Marijuana have changed my life significantly for the better, inspired me to learn, and land the job i'm at today. When I first started smoking it gave me a deep fascination of this world and all I wanted to do was learn more about it. Is it weird to say smoking weed motivated me and gave me a passion?
    This is obviously not the same for everyone else though.

    I first tried Marijuana at 14 and started using it pretty often around 15. I would smoke about every day(16-18) not because I was addicted, but because everyone was doing it.(Average California High School)(I'll add that from 16-18 I was using "Dabs" heavily which is the highest concentration of Marijuana)

    It was also a responsible way to have fun.
    I gained many new friends from smoking and it made me a lot more social.
    This seems unbelievable, but by senior year the entire class was good friends and there were the stereotypes of the "band nerds" who were smoking with the "football jocks."
    I was smoking with people who I would of never imagined hanging out with because Marijuana was a social common ground.(Sounds too much like the movie Breakfast Club while I type this out haha)

    To be honest there weren't many students who hadn't smoked in my class by Senior year. Even our Valedictorian had tried marijuana and many of our teachers openly had medical cards. I smoked with a few of my teachers once I had graduated too. I keep in touch with my entire high school class on Facebook and everyone is doing just fine.(Small town) I'll also add that our school had record test scores in the state so I wouldn't correlate learning capacity with Marijuana usage.

    Currently(24)I haven't smoked for over 8 months because of my gym routine though and I feel just fine. Physically and mentally I am above average and love the person I am.
    I would definitely do it all over again if I had the chance.

    In a country where obesity is silently killing everyone and people need their drug fix in the form of a cup of coffee every morning I just laugh when people are against legalization.
    I justify legalization since no one, but myself has the right to tell me what I can and can't do with my body.

    It's "The Land of the Free" last time I checked and I don't have time waiting for people to come to their senses on what I can and can't do.

    April 17, 2014 at 00:23 | Report abuse | Reply
    • Karebear

      This is to be expected. Some idiots ALWAYS try to discredit a cause when it finally sees the light of day! Marijuana is a NATURAL drug and has been used MEDICINALLY for 5000 years! I was smoking pot while in college from age 19 on up for 10 years. I did NOT get hooked on heroin, cocaine, meth, etc! The fact is the brain has STOPPED GROWING after the age of 18. The only thing it does after that age is continually LEARNING new facts, information, etc. And these study participants stated the pot smoking did NOT prevent them from learning and doing normal daily functions!! So I wouldn't put any weight behind this study at all. Marijuana SHOULD be legalized; it is LESS ADDICTIVE than alcohol and prescription drugs! BTW I do not smoke it now, but would prefer a joint to a cigarette now! BTW–I quit cig's 7 years ago–cold turkey! So I do know what I am talking about!

      April 17, 2014 at 04:48 | Report abuse |
    • FamilyDoc2

      "It was also a responsible way to have fun"? Based on the scientific results of this study, that is certainly not the case. And Karebear, the fact that something "is natural" and "has been done for 5000 years" or more does not mean that it is appropriate to continue doing so. There have been cannibals in the world for far longer than that, also murderers and almost certainly child molesters. Does that mean that we should allow those practices to continue? You will say "it doesn't harm anyone else!", but it has an effect on your family, and ultimately, if it becomes more widespread, this brain damage can affect society as a whole.

      April 17, 2014 at 08:11 | Report abuse |
    • Craig

      I dare you to pay for an MRI on your brain. Let me know the results.

      April 17, 2014 at 18:49 | Report abuse |
    • karek40

      Met a young man who smoked pot, I asked him how much he smoked, he replied whenever he wanted to, I asked on average how much do you smoke in a month? He replied about 4 ounces (at that time an ounce cost $100.00) I replied that's a new Cadillac payment. He drove an old vehicle that he had to work on all the time. He had 4 small children and they wore rags but he had his pot.

      April 18, 2014 at 22:53 | Report abuse |
  2. Mark A Brown

    Tracy: Dr. Spaceman, is it true that bread eats away at out brain?
    Dr. Spaceman: We have no way of knowing, because the powerful bread lobby keeps stopping my research.

    April 17, 2014 at 00:41 | Report abuse | Reply
    • BobbyG

      Looks like Whoopi's made herself another billion grivka.

      April 17, 2014 at 03:06 | Report abuse |
  3. justinbaileyforpresident

    So, after a person has been using pot for 90 days, their motivation centers are affected. Of course it is, I have seen a lot of pot heads in my life and most would not be called highly motivated. If you spent more than $5 on this research then you have wasted your money.
    The use of marijuana by anybody is to create a response on the body. An effect that some people seem to enjoy. They want to zone out and feel fine in a room full of cheetos or twinkies. Does this have a long term effect, sure, smoking cigarettes has cancer that will creep in and kill you, alcohol will destroy your liver, aspirin and tylenol also have nasty effects on the liver and kidneys.
    I don't smoke the stuff, but if the pot smokers want to then go ahead. Just don't drive stoned and kill others by being high and you will not see any problems with me. Just walk to the corner store instead, it is much safer and it will limit your purchases of chips and cookies to what you can carry home instead of buying out the store.

    April 17, 2014 at 00:57 | Report abuse | Reply
    • Bette

      I get high on purpose when I take road trips. Why? Because it helps to relax me and calm my nerves when driving in rush our/high congestion traffic so I can concentrate and focus. The number of times I have driven stoned...a few 100 probably. Have I ever come even slightly close to hitting someone or even getting hit...never! Also, not everyone gets the munchies so don't always assume the pot smoker is going to raid the corner store looking for the donuts. Pot affects everyone differently in a nut shell though if you were to statistically compare the deaths and accidents caused by pot vs. alcohol, drugs, fatty foods, cigarettes ect.... there is nothing to compare. 🙂

      April 17, 2014 at 09:52 | Report abuse |
  4. Andrew

    Not much can be concluded with a small sample size combined with a poor study design....More government propaganda...I thought we were over this?

    April 17, 2014 at 01:17 | Report abuse | Reply
    • Kate Johnson

      It's a horrible problem with medical reporting ridiculous claims without any real evidence. Making any claims based on that a tiny study that didn't even follow through with any kind of cognitive testing beyond reading brain scans, which with natural variation isn't an accurate method of determining anything, is nuts. We're talking about 40 people, but notice they don't tell you that in the article.

      April 17, 2014 at 05:37 | Report abuse |
    • Bette

      Yeah, and what exactly were the abnormalities??? I love hope they never elaborate or go into any detail with these kinds of studies. When there is little to no information on the research then you know it more than likely came from the government or a anti-drug campaign probably funded by a right wing conservative group. (not saying conservatives or republicans don't smoke, it's just rare)

      April 17, 2014 at 09:56 | Report abuse |
    • Steve

      sample size is not the issue here

      the issue I see is: claiming evidence for causal relations where the evidence is only correlational
      (maybe the brains of people who smoke were different to begin with; aka, 'selection effects')

      nothing wrong with saying the data are consistent with such causal interpretations,
      but its clearly wrong to claim evidence of causal relations just because the data are consistent with such claims

      April 17, 2014 at 11:06 | Report abuse |
    • FamilyDoc2

      Before commenting about the "horrible study" or "ridiculous claims", try clicking on the link and reading the actual study. This is not poorly designed and there are no outlandish claims. The data clearly show that there are clear differences in the brains of those who use marijuana, even occasionally, and those who do not. It could be that there were differences in those brains before ever smoking, but that would require another study. In the meantime, do we legalize marijuana so that teenagers and young adults can more easily obtain it and possibly cause permanent brain damage? Of course not.

      April 17, 2014 at 18:01 | Report abuse |
    • Craig

      The Journal of Neuroscience is one of the most respected medical journals in America. You may not like the findings, but for 40 years, "stoner" and "pot head" were short hand for someone with lowered motiviation and IQ than before they began hitting the bong. Welcome to reality.

      April 17, 2014 at 18:51 | Report abuse |
    • JT

      Famdoc – any teenager that wants pot can get it fairly easily, so why even bring that up as an excuse to keep cannabis illegal?

      April 18, 2014 at 12:28 | Report abuse |
    • FamilyDoc2

      But JT, legalizing it will certainly make it evern easier to get and also give the impression that there is no harm at all in using it. Teenagers will obtain marijuana and use it anyway, but responsible adults generally try to keep the irresponsible young ones from permanent harm, if possible.

      April 18, 2014 at 18:16 | Report abuse |
  5. Jeffro

    Horrible study. Sample size is to small, no control over the administration of dosages, or even a definition of what they are. "joint', what kind of unit of measurement is THAT? How many grams of pot in each joint? What concentration of THC? Were there significant variations of these vital statistics between 'joints'.

    Honestly, this sounds like they asked 40 college kids to fill out a survey.

    I would assume that being published in a journal of neuroscience, that the study itself wasn't so shoddy (even if 40 people is so small as to be virtually statistically useless), but the reporting of it is horrendous.

    Also disturbing is the totally undefined term 'casual use'. What would the equivilant be in beer? 1 beer = 1 joint? But a person drinking a single beer probably would have a mild buzz at best, but an infrequent smoker of pot would get ripped off of a 'joint'... or maybe not, since we don't know HOW BIG THE JOINT IS.

    What a waste of electronic storage media...

    April 17, 2014 at 01:21 | Report abuse | Reply
    • FamilyDoc2

      So if this study is "horrible", then describe an appropriate study whose results you would accept? Oh, you would only accept one that shows no ill effects from casual or regular marijuana use? I thought as much.

      April 18, 2014 at 18:24 | Report abuse |
  6. David

    Ha, I love it!
    And here the addicts were claiming that it "cures" illnesses and cancer. Unbelievable.
    They should look up marijuana and bullous lung disease.

    April 17, 2014 at 01:54 | Report abuse | Reply
    • Karebear

      No David, you moron! Pot is used as a PAIN KILLER for cancer! It doesn't cure it–no one has ever said it does! Pot makes having cancer pain more bearable! It also has MEDICINAL ACTUAL CALMING EFFECTS for Epilepsy victims using CBD (pure THC form). GET EDUCATED, you knuckle dragging neanderthal!

      April 17, 2014 at 04:59 | Report abuse |
    • Bette

      Yeah Dave, no one ever said it cured any of the diseases. It helps to alleviate the symptoms so you don't have to destroy your liver on prescription medicine and pain killers. Things that are considered legal are far worse for our health than marijuana. You sound like someone that would have been scared to death and believed every word of "Reefer Madness" as S stated, get yourself educated so you don't sound like a fool trying to debate against something you don't understand or have done any research on of your own, you just think by what some talking head has probably told you on TV.

      April 17, 2014 at 10:00 | Report abuse |
    • FamilyDoc2

      Karebear and Bette, more attacks on someone who disagrees with you when you have no better argument. Not a good way to prove your point.

      April 18, 2014 at 18:25 | Report abuse |
    • Eeyore

      Neither one of those folks has a single study to cite that will back up their claims and justify their indignant rants.

      April 18, 2014 at 19:02 | Report abuse |
  7. Thinking Clearly

    "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

    People with conservative tendencies have larger amygdala's too. Fact. There is no damage or harm, or anything proven here. CNN got casually hook, line, and sinkered into the age old reefer madness business.

    April 17, 2014 at 02:27 | Report abuse | Reply
    • Karebear

      Teabagger wingnuts tend to NOT have ANY brain matter between their ears! THAT is a FACT, Jack! Go put that in your pipe and smoke it–moron!! Just ask anyone at FUX who isn't a redneck.

      April 17, 2014 at 05:05 | Report abuse |
    • FamilyDoc2

      This article is not "reefer madness", but a scientific study on the differences in brain structure between pot smokers and non-pot smokers. Deny it all you like, but this study shows differences that could result in long-term brain impairment. You only get one brain.

      April 17, 2014 at 08:18 | Report abuse |
  8. David

    The study seems flawed. Here's why:

    1) 40 people is not enough. They do not represent as much biological and genetic diversity of the human species. Too small of a sample.
    2) There is no indication in the report (as reported here anyway) of the 20 pot smoking subjects did any other drugs, drank alcohol or took part in any other activity.Also did the subjects sleep regularly? Or have any other stresses in their life?
    3) No reported behavior or physical or psychological effects are admitted yet they saw "abnormalities" on an MRI. Are they talking mutations? New pathways? Dead cells? What does 'abnormal" mean? If there is no effect than how is it abnormal?
    4) Studying 18-25 year olds is a huge mistake. Their brains are not yet finished developing. They are a moving target. And we need to stop basing this type of research purely on folks in this age group.

    This is how the study should have gone (and it is nearly impossible to pull off):

    1) You would need a larger sample – thousands of people in fact. You would need a sample that represented the genetic and cultural diversity of the human species. This sample would have to be duplicated so you could have a control group with the same biological makeup. A diverse range of ages as well. You would also have to know their entire family medical history. Several generations of data in fact would be best.
    2) The study participants would need to be housed in a 100% controlled environment where every environmental factor could be controlled and measured. That includes: the air they breathe, the food they eat, the clothes they wear etc.
    3) Probably a good idea to not allow the group to use any sort of television or smart phone or computer during the study to rule out how those devices could effect the brain (radio waves, microwaves, radiation, etc)
    4) The study would have to be done over a period of years not days. 30 Years probably. 10 might be enough to get an idea.
    5) The drug would need to be controlled and dosage measured. Same dosage for everyone in the study.

    And this would just be to start. You would then repeat the same experiment with as identical as much of a group as possible and change dosage.

    Only looking at 40 people and measuring by "joint" is not enough (a joint is not a measurement). That's not science. That's a hobby.

    April 17, 2014 at 02:32 | Report abuse | Reply
    • FamilyDoc2

      This is a preliminary study, but shows significant effects. You are correct in pointing out that for a more definite conclusion there need to be larger and more extensive studies, but what you propose will take thirty years, would be far too expensive and also impossible to recruit participants who would agree to your study. It would also never get IRB approval, which is required for any study involving human participants. By the way, did you actually read this study before you totally rejected the results? A scientist never relies on a journalist's synopsis before coming to a conclusion. Your point about 18-25 year olds is ridiculous, as this study specifically was designed to evaluate the effects of marijuana on the still-developing brains of adolescents, who also typically engage in risky and taboo behaviors such as heavy marijuana smoking. Like most of the other posters here, you are simply denying the results of this study; your denial is mostly shrouded in pseudo-scientific criticism.

      April 17, 2014 at 08:28 | Report abuse |
    • Bette

      Ok , Doc. And please tell us that prescription drugs are better for us! We can't cure anything with diet either right? This article is a joke they don't even tell us what the "abnormalities" are. There is no denying an article if there is nothing in it to deny. Besides, you coming on here with the name Dr. trying to change peoples minds is far worse than people smoking, so kick rocks Doc.

      April 17, 2014 at 10:05 | Report abuse |
    • Brian

      FamilyDoc you're clearly an imbecile. This whole study beats around the bush without coming to any real conclusions as to the final outcomes. As you accuse all these posters of being in denial, you're being an anti-marijuana advocate who refuses to reep the possibility that these "abnormalities" have no serious effects on people.

      ITS A DRUG; all drugs bring about abnormalities with usage, however marijuana has still yet to have been recorded as any danger to the public besides this first extremely bias study in which the conclusion was "The next important thing to investigate is how these structural abnormalities relate to functional outcomes."

      You my friend, may need to toke one yourself and open up the mind a little. Cheers

      April 17, 2014 at 13:46 | Report abuse |
    • FamilyDoc2

      Bette and Brian, when you have no other argument it does not bolst your credibility to just attack those who don't agree with your opinion. Much better than agreeing with my post, your insults just prove the accuracy of my comment; thanks!

      April 17, 2014 at 18:07 | Report abuse |
  9. Garrett

    Alcohol doesn't just alter the brain.. it destroys it! If that nasty substance is legal.. there is NO reason that Cannabis can't. I'd rather be around Stoners than Drunks. Because at least Stoners have more control over themselves, typically more peaceful and know how to have a good time without being obnoxiously loud or inconsiderate of others around them.

    April 17, 2014 at 02:32 | Report abuse | Reply
    • Craig

      Good points! And I'd rather be around people who can speak with intelligence instead of the rambling, nonsensical drivel you hear coming out of potheads. But that doesn't mean we should legalize cocaine.

      April 17, 2014 at 18:54 | Report abuse |
  10. Docthal

    If you smoke enough pot, you get a little dumber, you get a little lazier. Everybody knows that, this just bring us a little closer to confirming it. I mean, all stoners know when they are baked enough they act retarted. Its just naive to think that you can bring youself to that point and then have 0 residual effects afterwords.

    April 17, 2014 at 02:48 | Report abuse | Reply
  11. Karl

    So people tracked and recorded their own consumption.. Not that I really see any point to this reserch but it should at least be done in a corrent manner. Did the subjects smoke with or without tobacco, by burning or by vaporizing, is "joint" a accepted term aposed to say ohh I dont know.. Gram.. This just reaks of stupidity..

    April 17, 2014 at 02:58 | Report abuse | Reply
    • JT

      Stupidity is certainly one possibility. I'm on the fence between naive about the effects of drugs, super eager to have a paper published, and intended to prevent legalization efforts. I don't think the advancement of science or human knowledge was really part of the consideration.

      April 18, 2014 at 12:31 | Report abuse |
  12. ddgirl13

    Why ask the users if their relationships are suffering? They are usually so high they don't event notice how much of a loser they are becoming. Ask a mother, girlfriend, teacher, boss, etc. I'm sure you would get a different response.

    April 17, 2014 at 05:34 | Report abuse | Reply
  13. qckslvr

    Saundra Young,CNN Medical Senior Producer,Should be embarassed to put her name on this article! Does she know anything about scientific methods,probability,statistics? A ridiculous sample size of 40?Specious research? Give me a break!

    April 17, 2014 at 07:37 | Report abuse | Reply
  14. HipHarold

    I smokt a lto of pot in the sexties. Didnt seam to effect me atol.

    April 17, 2014 at 07:54 | Report abuse | Reply
  15. The Nurse

    " 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"

    April 17, 2014 at 08:16 | Report abuse | Reply
    • DP44022

      I wonder if casual alcohol use may cause damage to your brain??

      April 17, 2014 at 09:15 | Report abuse |
  16. bry

    Very probable that pot use affects your brain adversely – is that a surprise to anyone? The question is how much damage in relation to how much use. For most people even moderate usage would not produce any noticeable development problems or adverse effects.

    But if the government's goal is to identify all drugs that may affect our bodies in negative ways I am happy to listen to them as long as they start recognizing the most destructive drug known to man – alcohol. Compared to alcohol smoking pot causes trivial body damage while alcohol damages every organ in the body. And this isn't even factoring in the cost to society and related crime rates. I don't think there has ever been a marijuana-fueled riot – ever. A group of people smoking a bunch of pot is more likely to snack and watch a movie rather than cause a big disturbance. Now think of the violent encounters and parties-turned-riots fueled by alcohol or the number of alcohol-related car accidents.

    April 17, 2014 at 08:18 | Report abuse | Reply
    • twitch


      April 17, 2014 at 09:57 | Report abuse |
  17. Salty Dog Walter, Scourge of the Seven Seas!

    Aye, laddies, this reminds me of a time when behaviour such as this was more public, and not too many people cared. But ol' Walter cared, for I knew the dangers of this long before medical science conducted its findings. Thus, whenever I encountered someone toking on a gnarly out in public, I'd hurl feces at them. Nothin' makes a bloke stop puffing like a cow pie to the face, especially a nice fresh one that splatters. Aye, those were the days. Me thinks it may be time for a trip to Colorado, and relive such shennanigans again.

    April 17, 2014 at 08:54 | Report abuse | Reply
    • Sandeep

      Marijuana/Ganja/Hemp/Cannabis/Cali as you know it was viewed not just as a plant, but a HERB with unimaginable therapeutic properties for tens of thousands of years! Times have changed and times are strange; here comes the modern science in the 19th century. And you say, "I knew the dangers of this long before medical science conducted its findings???" Yeah! That's what an alcohol-binging feces-hurling retard can do and be proud of! It shows that although Marijuana could have saved your sorry existence and make you respect your race, you opted out and acted this way.

      Cannabis has been used for thousands of years for treating asthma, cancer, rheumatism, epilepsy, various skin conditions and hundreds of diseases. Hemp is an unbelievable super-crop that we can wear, eat, build, and also cure! Check out few links about them; use google to search for anything related to cannabis and you should get it.







      Watch this, do your research and get a life!

      April 19, 2014 at 06:30 | Report abuse |
    • Eeyore

      Sandeep, videos aren't research. I can post a video of a cat playing the piano. It proves not a single thing. If you have peer-reviewed studies you can cite, then cite them. Otherwise, you just look stupid.

      April 19, 2014 at 09:26 | Report abuse |
  18. Kenny Dwit

    too funny! the u.s. government has a patent on pot that says it protects the brain.

    April 17, 2014 at 09:04 | Report abuse | Reply
  19. DP44022

    I wonder if casual alcohol use may cause damage to your brain??

    April 17, 2014 at 09:16 | Report abuse | Reply
    • Eeyore

      Why don't you do some research and read the studies that have probably been done on it?

      April 18, 2014 at 19:27 | Report abuse |
  20. Kim T

    You're right, free thinking IS something the world should be concerned about. Weed opens the mind while every influence of basic society is orchestrated to breed sheep and conveyor belt copies of the same little slaves. Wake up.

    April 17, 2014 at 09:36 | Report abuse | Reply
    • Eeyore

      Oh, malarkey. There's nothing enlightening about smoking pot. Don't be ridiculous.

      April 18, 2014 at 19:28 | Report abuse |
  21. twitch

    I will just leave this for the ones who believe this propaganda.


    April 17, 2014 at 09:57 | Report abuse | Reply
  22. caliboss

    the greatest plant in the universe is almost free, LET FREEDOM RING! 13

    "any doctor against marijuana is a doctor of death" – cali secret 420

    from 0 states to half the country, from low 20% approval to almost 70%, cali runs this planet by 2 decades, time to tie marijuana to the 2014, 2016 elections, out with the old, in with the new

    20 years behind us southern states, sad and scary....nobody denies freedoms like the south, nobody…the top ten incarcerators on the planet are southern states...even if marijuana reforms did pass the republiCANTS in charge would deny you all your freedoms, centuries of practice...no matter though, we never planned on getting your backwards brethren from day one, half the country already but not one southern state, lol...not 1….the new generations are taking over in the south and they are nothing like their freedom denying parents, let’s ride…

    Deaths by Alcohol and Tobacco: Millions
    Deaths by Prescription Drugs: Quadrupled in last decade
    Deaths by Guns: Millions
    Deaths by the food we are fed: Millions
    Deaths by Marijuana: 0, ever...they are killing my American family while denying freedom

    Marijuana Super Bowl, Marijuana on Easter Sunday (4/20), MARIJUANA 2014!!!

    love and freedom forever


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

    Familydoc2 Did you just compare smoking pot to child molestation?...

    April 17, 2014 at 10:43 | Report abuse | Reply
    • FamilyDoc2

      No, simply making the point that just because a behavior has been going on for thousands of years doesn't mean that it should be legalized. I assume that most people are against murder, cannibalism and child molestation, and would agree that they shouldn't be legalized.

      April 17, 2014 at 18:11 | Report abuse |
    • JT

      Do you think it helps your argument to be pendantic? Comparing smoking marijuana to child molestation – even in a generalized context of "a behavior that has existed for a long time" is pure hogwash. There's no need to even bother explaining why, since it's apparent from your choice of counter example that you are more interested in "winning" an argument than acutally debating one.

      April 18, 2014 at 12:36 | Report abuse |
    • Eeyore

      I don't think you have a clue what the word "pedantic" even means. Family Doc has made a number of excellent points and the people here who are the most upset about them have been unable to counter any of them.

      April 18, 2014 at 18:54 | Report abuse |
  24. Logic

    The big assumption everyone is missing here is that being unmotivated is a BAD thing. Maybe pot is just helping people to realize there is no reason to get stressed over little things. To quote Bill Murray's character in "Meatballs", sometimes "It just doesn't matter".

    April 17, 2014 at 11:35 | Report abuse | Reply
  25. Jim

    It's called dope for a reason.

    April 17, 2014 at 11:54 | Report abuse | Reply
  26. Jennifer

    Why didn't they cross-compare this study with SENIORS who have been casual MJ users since their teens? That would make far more sense.

    April 17, 2014 at 12:04 | Report abuse | Reply
  27. slickdick

    This is quite biased. like most of CNN and other large news organizations like Fox. they did not put into consideration the use of alcohol in the tested individuals. which is used by most college students. This is just another ploy to stop people from voting to legalize, which would help our economy thrive.

    April 17, 2014 at 12:20 | Report abuse | Reply
    • Eeyore

      CNN didn't do the study, doofus. Did you even read the actual study, as opposed to simply skimming the CNN article ABOUT it?

      April 18, 2014 at 18:55 | Report abuse |
  28. Jimmy Limo

    "None of the users reported any problems with school, work, legal issues, parents or relationships"... Would you be able to say that if the test subjects got DRUNK 6 times a week ? HELL NO !!! So what's wrong with a little brain CHANGE ? The researchers said it CHANGED the brains, didn't say DAMAGED the brains.... Change is GOOD !

    April 17, 2014 at 13:33 | Report abuse | Reply
  29. P5yl0

    Change yourself!
    Change the World!
    When marijuhana changes people do it!
    Cause when you look outside.. this world has some Problems!
    What is the Way.. Change!

    But the most peoples have FEAR of Changes...

    @Jimmy ^^ thumb up!
    Change is Change.. not DAMAGE!

    April 17, 2014 at 14:27 | Report abuse | Reply
  30. J Varnos

    This study was funded by the NIDA and ONDCP. That's all anybody needs to know. This is junk science (just how our government likes it when it comes to marijuana).

    It was nothing but an MRI study, and by the way.... common table sugar lights up the same areas of the brain in the same way. Any food scientist from the huge processed food industry can tell you that. Funny that nobody is screaming that table sugar causes brain damage.

    April 17, 2014 at 15:08 | Report abuse | Reply
    • Mark

      The problem is that the majority of the voting public in America are low informational and have no idea... they just eat up propaganda like kids and sugar cereal. Nom nom nom...

      April 17, 2014 at 22:32 | Report abuse |
    • Eeyore

      @J Varnos: how is this "junk science"? What is flawed about the study?

      April 18, 2014 at 19:33 | Report abuse |
  31. Erock

    Your brain is rewired whenever a habit or lifestyle change is implemented. If I eat broccoli in the shower for the first 15 years of my life you better believe I am going to be thinking of broccoli every time I step into that shower even if I kicked the "broccoli habit". A very basic example of "wired" neural transmission. This entire article is grossly oversimplified and who are you to say that this way of thinking is not superior to our current way of thinking?

    April 17, 2014 at 15:27 | Report abuse | Reply
    • Eeyore

      Do you have any evidence that it is? Where is the research that shows it?

      If you don't have any facts that refute what the study shows, why bother posting?

      April 18, 2014 at 22:30 | Report abuse |
  32. Alex K

    It is possible that the changes occurring in the brain are beneficial. The article seems to stress that changes *are* occurring in the brain, which will happen with *any* drug, including something like SSRIs (anti-depressants). What the research doesn't seem to cover is whether these are good or bad "abnormalities." I recently read that a woman studying Einstein's brain discovered it was missing a particular fold - an abnormality. However, I think most would agree that this was a *good* abnormality that allowed that particular person to process information in a novel and beneficial way. So, who is to say the chemical changes brought on by cannabis are negative?

    April 17, 2014 at 15:36 | Report abuse | Reply
  33. dylan

    did they make assumptions about iq's and strokes off current research...what are these conclusions based off of? because this study isn't done over long periods of time to determine whether or not the people in the study are going to have a stroke 30 years from now. scientists have had more than 30 years to study this drug and they havent so why are people curious now? because we want it to be legal? really sounds like a bunch of propoganda from people who dont want pot legal....no one complains about the liver disease WE ALL KNOW you will get from drinking sooooo any anti marijuana material is generally a load of scare tactics

    April 17, 2014 at 16:23 | Report abuse | Reply
  34. Anon

    Ah, looks like the corporate giants are out again to spread some propaganda. Too bad that we don't fall for that as easily as people did in the early 20th century, so we know all this is just some article that is meant to scare people into thinking legalization is not the way to go.

    April 17, 2014 at 16:25 | Report abuse | Reply
  35. SueVo

    Saying that this means "bad things" is bad science – considering they haven't studied the consequences of the enlarged sections: http://blogs.columbian.com/cannabis-chronicles/2014/04/16/questioning-a-study-on-pot-and-brain-changes/

    April 17, 2014 at 18:10 | Report abuse | Reply
  36. Bud Smoker

    Children should never use drugs but unfortunately there is a trial period for most youths. When I was young brain damage was just another Friday night with pizza and beer. Oh yea, I forgot about the graphic's bong. We all lived to inhale another day. At the time we were just trying to have a good time. Most of the bad times I can recall center around alcohol and problems with the opposite sex. I don't know the answer, pot keeps you at home and out of trouble. It could be worse, like paying for child support at an early age or multiple DUI's. I guess if I could do it all over I wouldn't have smoked as much and I definitely would have avoided alcohol all together. Sometimes a person has to live life and learn from our miscues.

    April 17, 2014 at 18:56 | Report abuse | Reply
  37. freethinker

    Let us attack the real substances that negatively affect our society such as alcohol, processed food, and pharmaceuticals...These are real dangers to be concerned about. People in power want you to fear and boy are they good at it! And for the record, CNN is not a good source for facts, nor is any so called news outlet...but that is a battle for another day...

    April 17, 2014 at 19:40 | Report abuse | Reply
    • Eeyore

      Oooooh, "the people in power!" Please, knock off the hyperbole, dear. It's laughable. This is a study done by researchers. The results are the results. It's a preliminary study and it wasn't done by the government or the "people in power."

      April 19, 2014 at 09:23 | Report abuse |
  38. Mark

    So a study paid for by the Drug Czar? Conducted by addiction "specialists"?

    As neuropharmacologist and researcher Gregory Gerdeman told USA Today:

    "If you're getting money from the drug czar's office, that money's not going to continue if you don't end up publishing something that at least supports the general story of the danger of drug abuse," Gerdeman said. He says he doesn't necessarily doubt the research, but says it should be looked at with a certain amount of caution. ""If it were my child, even with this study, I'm more comfortable with young people having a casual marijuana habit than drinking regularly."

    April 17, 2014 at 22:29 | Report abuse | Reply
    • FamilyDoc2

      That quote is what it is: one expert's opinion. I might ask who is providing his paycheck so that we could know his potential biases on this subject matter.

      April 19, 2014 at 06:55 | Report abuse |
  39. swyrlpr


    April 18, 2014 at 00:38 | Report abuse | Reply
  40. Alan Bernstein

    "None of the users reported any problems with school, work, legal issues, parents or relationships..."

    The study actually claims to show "changes," not damage. And yet, from those posting comments supporting continued prohibition, it's all about the damage.

    April 18, 2014 at 00:53 | Report abuse | Reply
  41. Mike Watts

    Really? 20 people can draw you to that conclusion? Lmao CNN is a joke for this. Why don't you guys issue these type of articles about prescription drugs and booze? Wait, you support the status quo bc it financially benefits you to support the obvious bigger dangers and put emphasis on things that don't really have much of an impact. Tragic that news has just became entertaiment

    April 18, 2014 at 05:12 | Report abuse | Reply
    • FamilyDoc2

      20 people shows there are considerable changes in the brain, and it is dose dependent. Does this happen to everyone? This study doesn't prove that, but given the results a much larger study should be funded, and with some attempt at showing the changes in brain function that could be the result of these changes. Click on the link above to the actual study, if you dare, and read the methodology, results and discussion. As I replied to others, what type of study on this subject would convince you to accept the results. Oh, of course, only one that showed no changes or harm from marijuana use, and even better one that only showed positive effects. It is not science when you only accept experimental results that agree with what you "know" to be true. In my opinion this is what results when you teach creationism as science, and poor education is doing far more to ruin this nation's future than any actions of the current occupant of the Oval Office. Of course, legalizing marijuana may accelerate that much more, and this study shows that the effects of marijuana need to be studied much more thoroughly before we embark on wholesale legalization.

      April 19, 2014 at 07:42 | Report abuse |
  42. emmanuel ezeala emex

    Smokeing sucks

    April 18, 2014 at 14:07 | Report abuse | Reply
  43. stel1776

    Here is a good article regarding this study and its many flaws:


    And another:


    April 18, 2014 at 14:49 | Report abuse | Reply
    • Eeyore

      And these are opinions. Not studies. Do you have any studies that show that marijuana doesn't cause changes in the brain? If not, do one. If so, cite it.

      April 19, 2014 at 09:21 | Report abuse |
  44. Cliff

    Yeah, all those artists and musicians are clearly deficient mentally. And let's not forget the gobs of rich and famous people (i.e. successful) that imbibe it regularly. It is all but known that the rich and powerful imbibe cannabis regularly. But who cares right? Some study, that took all these years to find this out (if you believe that than maybe you should not use pot because you are brain dead) has come out just as marijuana legalization is so achingly close to being legal. Thank God for that lol. If you dunces don't see the forest from the trees that is fine. But any of you come around telling me I am mentally retarded from smoking I will pop you in your nose lol. The real reason marijuana is illegal is because of hemp. Look up your history and stop being a fool. This government and big business don't want legal because of textiles etc. not because people like to get baked. So stupid. Yeah, please don't smoke weed. You are all too stupid to handle it probably lol.

    April 18, 2014 at 15:14 | Report abuse | Reply
    • Eeyore

      What drivel. Is that what pot did for you?

      April 18, 2014 at 18:58 | Report abuse |
  45. Cliff

    Funny how easy it is to get the average citizen to fear and loathe the unknown. You all need to get a dog. You are probably scared of your own shadow. Your government lies and regularly bribes "experts"...get a clue on how this works.

    April 18, 2014 at 15:23 | Report abuse | Reply
    • Eeyore

      How does it work, dear? Got a conspiracy theory, do you ? Quelle surprise!

      You don't have two brain cells to rub together. Your posts provide plenty of evidence that pot smoking makes people stupid.

      April 18, 2014 at 19:00 | Report abuse |
  46. Seattle Guy

    Who cares!

    April 18, 2014 at 15:40 | Report abuse | Reply
  47. Nancy

    Study was sponsored by conservative anti-legalization groups. The study fails to mention enough details. Too small a sample group and not time frame is not long enough. Lame for CNN to even publish.

    April 18, 2014 at 17:27 | Report abuse | Reply
    • FamilyDoc2

      If you click on the link in the article above you can ready the actual study as published, and there are a plethora of details. As for the study design, this is a preliminary study in humans designed to show if there are brain changes similar to what has been observed in rat brains under similar drug use. The correlation is important because the animal studies include brain dissections, which are much more difficult to arrange in human subjects. The time frame was certainly long enough to show differences between the brains of users and non-users. What study design would actually meet your satisfaction? I suspect only one that gave the results you obviously desire.

      April 18, 2014 at 20:20 | Report abuse |
    • Eeyore

      Nancy, what are these "groups" to which you refer? Give us their names. Show proof that the research was done for spurious reasons. Go ahead. I can hardly wait.

      April 18, 2014 at 21:19 | Report abuse |
  48. Curlee

    The stock photo is hilarious. Only guys with scraggly facial hair smoke pot. Lol.

    April 18, 2014 at 19:38 | Report abuse | Reply
    • Eeyore

      So nobody who smokes pot has a scraggly beard?

      April 18, 2014 at 21:17 | Report abuse |
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