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."
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What is the difference between tetrahydrocannabinol and a cannabinoid? How are the cannabinoid recepters in the brain effected by these two chemicals? Tetrahydrocannabinol is found in marijuana and cannabinoids are found in both marijuana and human breast milk. Why is one chemical harmful to a developing brain while the other is essential to proper development? This aritcle raises many questions.
There is also the question of whether the observed brain differences existed prior to pot use – and may be related to why some people use and others don't.
The problem with a lot of these studies is that they use people who are already using. They need to start with scans of kids before use, then compare years later relative to subsequent pot use.
This study is nice, but unrealistic as far as what substances people are going to put in their bodies. In the late sixties I was visiting a friend who is a neurologist and he allowed me to see some of his research on habitual drinkers. It was quite alarming to see that someone that drank alcohol on a regular basis had brains that had shrunk to a third of their original size. Based on what I saw then I am amazed that anyone could function with their brains literally shrunken. I think we've all seen the damage cigarettes do to every part of the human body. Most of the food presented to us for consumption is truly poison and over time does incredible damage to our bodies. Aspertame is proven to cause severe brain disease and yet it is legal for consumption. All of the above substances are consumed by a substantial number of people of ages 12 and up, yet they are legal. My point is that if the above substances are legal, even with the above study quoted there is no logical reason for them being legal and pot not to be legal.
Unrealistic is trying to dispute facts with babble.
Ignorance is labeling things you do not understand as babble.
Here we go. The "backlash" to the long-overdue decriminalization of marijuana. We're apparently back to: "This is your brain. This is your brain on drugs. Any questions?" Which, of course, was paranoid and hyperbolic propaganda, and, with respect to pot, had no scientific basis then – or now. As others have noted, too much salt, sugar, etc. can mess with your brain, too. Should be make them illegal?
I'm surprised anyone would take this article (a test group of just 40 people?!?!?!) seriously.
What if the test group of 40 people had supported the notion/theory that frequent marijuana use is beneficial for maintaining good health? Would that have made you feel better?
40 people is actually a decent sample size considering that all 20 of the folks in the "used" half of the group showed affects. It gives you a margin of error of around +/- 5%. Just because you disagree with the numbers doesn't mean they are wrong.
"lead author and a researcher in the Massachusetts General Center for Addiction Medicine"
That's all you need to know.
So 40 College Students were tested for smoking "joints"? Im going to take a wild guess and say that the 20 "smokers" werent just smoking "joints". Also, call me crazy, but what about the alcohol and other substances they could have consumed with in that 90 day period? I won a few science fairs back in my day and I remember that you have to have a control group to test these hypothesis. so unless all 40 were given the same amount of food and beverage this whole study is BS.
Not enough people in the group. Didn't say which chemical caused the problems. There are about 450 chemicals in the plant that need to be researched further.
Also, this report is a little biased. You have to consider the personal opinions and positions of the researchers. Google the individuals that completed the study.
Still, it remains. Why does the U.S. Government have a patent on Marijuana?
US Patent 6,630,507 Cannabinoids as Antioxidants and Neuroprotectants
"Cannabinoids have been found to have antioxidant properties, unrelated to NMDA receptor antagonism. This new found property makes cannabinoids useful in the treatment and prophylaxis of wide variety of oxidation associated diseases, such as ischemic, age-related, inflammatory and autoimmune diseases. The cannabinoids are found to have particular application as neuroprotectants, for example in limiting neurological damage following ischemic insults, such as stroke and trauma, or in the treatment of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease and HIV dementia. Nonpsychoactive cannabinoids, such as cannabidoil, are particularly advantageous to use because they avoid toxicity that is encountered with psychoactive cannabinoids at high doses useful in the method of the present invention."...
The experiment used an extremely small sample size; less than 50. It couldn't show that these "abnormalities" were in fact negative, it just ASSUMES so. And no one has reproduced these research results yet.
Color me underwhelmed.
i am 53....have smoked weed EVERY day for last 33 years, usually 20 joints a week......own my own business and make excellent money......do not lack motivation or critical thinking ability skills......am in full control at all times of ALL my faculties....am successful in my personal life as well......am in superb health mentally and physically, look 15 years younger than what i am.......live a low stress easy life.....am not a criminal or deviant of any sort.......am honorable and have integrity.....all my neighbors love.........animals trust me, i hand feed the rabbits and sqirrels and birds in my back yard..........can still run full bore and stride however for shorter distances from when i was twenty..........doing the best i can to identify a shortcoming from having been a weed smoker for so long yet i cant think of one thing that has been detrimental from having been a weed consumer.
Same here.... been smoking regularly since I was 19, and Ive been in IT for the last 20 years.
I fix your computers after your break them....
I know of many like you. You, sir, are my type of person. With all the squirrel, bunnies and bird bonding, It was a great offset from the professional persona. Balance is key. I sometimes utilize the herb to achieve a balance.
And see you at WSP! 🙂
what he said
You've overlooked a severe lack of humility as a possible flaw.
I think you missed the point of the study.
Yes you might be successful and in good health, even after smoking all that devil weed.
But if you hadn't been smoking so much
You COULD have been like Warren Buffet and the Six Million Dollar Man on crack...
You really could have been so much more...
but alas, another life wasted...
"...have smoked weed EVERY day for last 33 years."
Please explain how willfully violating federal law on a daily basis makes you "honorable and with integrity."
Interestingly enough no side effect when it came to day to day life
I know it is difficult to control human studies, particularly with something as time intensive as MRI, but it is impossible to eliminate the possibility here that the smokers were inherently different from the non-smokers from the beginning. The fact that the experimental group consumed more than 2x the amount of alcohol as the control group is an undesirable variable as well. It would be interesting to see if this study can/will be replicated by other groups. Maanirantel, I agree, the small sample size is pretty undesirable as well!
You know what makes people stupid? Listening to any of these "news" outlets of America. Just because you are owned by people who originally LIED to America to get Marijuana illegal, you will do anything in the world to make it look bad... Hey maybe you can spin the Flight 370 story you have been kicking around like a dead horse for 5 weeks and say the pilot was smoking a joint while flying. You lie about everything else and put yo0ur "spin" on it anyway.
The problem with this study, and so many like it, is they start too late then assume, " 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." The study subjects were already users, maybe they had those issues prior to use, and may have been what prompted their use to begin with such as ADD, ADHD, or one of the many other ailments that can cause the issues. For any REAL SCIENCE you must start with an equal panel of test subjects with before and after scans, or whatever measurement is used. Simply testing the difference between users and non-users is not enough. It must be the difference between before and after use in comparison to never used.
This is ridiculous
I have smoked for decades and suffer no ill effects.
My friends who were drinkers are all dead now, mostly from liver and kidney damage by alcohol.
Me, I'm in better health now than I was twenty years ago.
And wake and bakin' each morning
The headline uses the word "damage" but that word does not appear in the story, does it? The report finds "changes". Changes can be good, bad, or neutral. Reporters reading this much and writing it up as "damage" must be smoking something.
I've smoked regularly since 1972, and not a little bit. I've worked in IT the entire time for two major corporations In all those years I've known four people who literally drank themselves to death. Others who drank themselves out of a job. Several others who smoked cigarettes that contracted lung cancer. Don't know anyone who smoked weed that died or lost their job.
Hardly a "Study" with only 40 people.....
Let's discuss the effects of not drinking alcohol versus having three drinks a day. While I have no doubt that too much marijuana in a period of time is bad for you, so are a great number of things. The key to almost everything in life is moderation and finding a balance/compromise. I would be interested to see the same research group provide analysis and recommendations on occasional use in moderation.
Correlation is not causation. maybe smarter people are less likely to smoke grass?
Tell me this, how can something that is found naturally be so "dangerous"? I mean what about all the medications people take to feel "better" or all the crap that people snort or shoot themselves up with? Arent those more "dangerous" then something that is natural. Or how about cigarettes that actually for the fact that can give you cancer. Or the alcohol that can give you liver cancer? The benifets of smoking a joint actually does help many feel more better then taking so much pills. It has helped save more money then being on medications.
Not everything natural is safe. That is a silly notion. Would you eat a nightshade plant???.
This study was promoted and funded by every anti-drug organization in this country and should not be taken seriously. There are Several errors throughout this study besides it's prejudicial leanings towards the anti-drug platform.
Also any study worth it's weight will use more than 20 test subjects... What kind of survey testing was this, a high school project?? This whole study is a BIG PILE OF BUNK!!
First off, this article explains that this was a cross-sectional study, and then goes on to make a longitudinal study claim.
Secondly, our brains are constantly rewriring themselves so how is that a bad thing?
It's ridiculous how ignorant people will be about things they know nothing about
Here we go with the scare tactic studies.
For the Pot arguments especially for legalized casual pot, is the statement that it is safer than smoking and drinking... However Smoking and Drinking isn't really that safe to begin with. We tried prohibition to stop it, the problem is that both are too integrated in our culture to illegality it. Making causal pot legal isn't a step in the right direction, as we try to further limit smoking and drinking.
I would argue that the negative effects of marijuana prohibition far, far outweigh whatever negatives are inherent in using the drug itself.
I'm scrude! See?
Ok I don't know one adult smoker who thinks teenagers should smoke copious amounts of cannabis,most of know better than any study what effects it'll have on kids.Now on to the real meat ;adults.Don't try to scare me into giving up weed.The suggestion ,and all it is is a suggestion,is that pot will make you dumber and cause brain cell damage.Well let me see Carl Sagan,William Burroughs,Montel Williams, all regular pot smokers(at least once a day) and all great critical thinkers.I think I'll keep on smoking my medical.And I didn't even touch on the most recent studies on the effect of Cannabis on cancer coming out of Spain and the UK.I won't elaborate except to say my uncle was diagnosed with Prostate cancer last year that was called "aggresive".When his doctor looked to see if the cancer had spread elsewhere he was amazed to find out that it was contained solely in the prostate.Why?My uncle is a regular Cannabis smoker and a perfect example of how THC cuts off cancer pathways;as was recently discovered in the UK.So you can take your one study and toss it ,do some real science or the spirit of Sagan will haunt you.
Misleading headline. They haven't found evidence of damage, they've found evidence of change. Maybe the change is positive in some people.
I feel this study had a goal in advance. Too many extra variables that make it highly questionable. They use "scientific" studies to prove anything these days.
I hope that Sanjay Gupta and his team read the Journal of Neuroscience and CNN's The Chart.
His advocacy for the legalization of marijuana is not based on sound science or long-term investigation.
I can't believe no one else has mentioned the ridiculously small sample size – 40 young adults between the ages of 18 and 25...
Great job with the textbook scare-tactics headline CNN. Funny how the study made absolutely NO MENTION of brain damage. I guess Sandra was reading between the lines or using poetic license or something...
The idea that those who smoked earlier in life went on to have judgement issues and lower IQ's than normal, might not be an effect of marijuana use. Perhaps early marijuana use is indicative of poorer judgement and a lower IQ.
Don't get me wrong, I'm a regular user and started earlier than 16. And while pot might dull my math skills, it also affords me a perspective I don't have otherwise. Some of my greatest ideas come to me while I'm high – seriously.
Can you define "casual". Is this once per day or once per week or what? Also, are the test subjects drink pepsi or coke products? How about eating sweet and low and splenda and equal? Do they do any alcohol or hard drugs? If not smoking I'll chew on my pot. I heard it helps prevent cancer.
Perhaps the author of this article smokes too much to catch typos in their own article...
Maybe some people smoke marijuana because they have something wrong with their brain and not because they smoke marijuana.
"says Dr. Jodi Gilman, lead author and a researcher in the Massachusetts General Center for Addiction Medicine."
Correlation or causation?
quote 1: "Dr. Jodi Gilman, lead author and a researcher in the Massachusetts General Center for Addiction Medicine..." Not an impartial, unbiased, or scientific source.
quote 2: 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..." is this science? Sounds like they had a goal in mind and back-filled the science to prove their point.
Looking forward to the day when there is real research by ethical scientists free of an agenda.
Actually you have to start any research with an objective. In this case the objective was to see if changes in the brain occluded, which they did. If they cherry picked from the results and discarded results they didn't like, that would be biased reporting of the evidence. Further I see a lot of knee-jerk comments on here accusing the researchers of incompetence and other things without any sort of proof. All the researchers says is that they say the changs in these people's brains. They have made no forecasts as to how the changes will affect the people long or short term. They in fact say that confirmation and follow- up studies need to be done.
I'll take it any day from the change that alcohol does to you. Keep watching those beer commercials where life seems so grand and full of pretty women
The study says marijuana may alter, not damage your brain. It's probably true, but the implications of that are... none. Pretty much everything you do alters your brain; learning alters your brain, aging alters your brain.
The study says that "so little is known about the effects of marijuana on the brain." Well, thats probably because we know pretty much nothing about the brain in general.
When studies are funded by the same agencies that have an agenda to keep the mindless war on drugs going and wasting the taxpayers money, the results will be viewed as nothing other than keeping the hysteria active and their jobs secure.
who funded the study? I smell a conflict of interest (I mean, besides the author's day job...)
if anyone is interested in finding genuine, real information about marijuana.. i urge you to check elsewhere.
Nothing to see here, folks, move along. This piece is nothing but fear-mongering propaganda. When the pea gravel installer came to my house last week to take measurements for the winding deck area around my pool, he made about 12 length x width measurements and jotted them down. As he was using his calculator to tally the area up, I had the answer before he was finished, using my brain, which has been exposed to 38 years of casual use. Try again, Dr. Gilman.
If the researchers are reputable scientists (and I think they are), they know how arbitrary their measurements are here in the study. Some students smoke 20 "joints per week." How big a joint? "How potent was the marijuana in the joint?" How much of the joint did they actually inhale?" "And for how long?" Did none of the marijuana users ever smoke a pipe or a bong? It's rare for college stoners to only ever smoke rolled joints, so how did you measure exposure?
Sorry guys, but this study smacks of researchers having a conclusion in mind when they start the research, and designing it to get the results they've already gotten their hearts settled on.
The money trail funding this Dr smells like some kind of pork product...look at the wording: "...very careful about legalization policies and possibly consider how to prevent anyone under age 25 to 30 from using marijuana at all."
I was gonna read all of this...but then I got high!
Does anyone else think that the median number of "joints" smoke per week was 6? I mean one person smoking an entire joint is insane. You would be blasted! That's like drinking a half pint of whiskey. 20 joints per week? I mean that's totally insane. Seriously, who smokes that much?
I see a lot of concern about grass becoming as ubiquitous as alcohol and it affecting young brains in very bad ways. However,I don't think (there is that useless term again) there would be much dissent with the next few ideas. Alcohol has destroyed entire families, careers, relationships and more than I care to enumerate here. It kills, without mercy. Yet there is no unified effort to educate and treat. It is pointless to discuss grass and its negative consequences without putting alcohol on the same playing field. Alcohol will continue to destroy lives and this debate will go on without any real answers.
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."
Doctors: That is not yours nor governments decision to make! What people of legal age (18+) do personally in our own homes with no impact to others are no concern of anyone's, and should be a fundamental right of all Americans.
YOUR JOB as a doctor is to do your job by perfoming studies like these that provide the public with scientific, unbiased, perr-reviewed data that we can use to make our own decisions on what we can do to our own bodies. Thank you.
They only say "may" damage your brain because "most certainly" would disrupt the current lobby, ruin a potential tax gold mine and destroy a whole new branch of the tobacco industry. In other words, 'Think of the money we'll make! We can deal with the fallout later, dudes.'