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Marijuana Use Dampens Brain's Response To Reward Over Time

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ANN ARBOR—Most people would get a little 'rush' out of the idea that they're about to win some money. In fact, if you could look into their brain at that very moment, you'd see lots of activity in the part of the brain that responds to rewards.

But for people who use marijuana, that rush just isn't as big—and gets smaller over time, a new study finds. And that dampened, blunted response may actually open marijuana users up to more risk of becoming addicted to that drug or others.


The new results come from the first long-term study of young marijuana users that tracked brain responses to rewards over time. It was performed at the University of Michigan Medical School.


Published in JAMA Psychiatry, it shows measurable changes in the brain's reward system with marijuana use—even when other factors like alcohol use and cigarette smoking were taken into account.


"What we saw was that over time, marijuana use was associated with a lower response to a monetary reward," said senior author and U-M neuroscientist Mary Heitzeg. "This means that something that would be rewarding to most people was no longer rewarding to them, suggesting but not proving that their reward system has been 'hijacked' by the drug, and that they need the drug to feel reward—or that their emotional response has been dampened."


The study involved 108 people in their early 20s—the prime age for marijuana use. All were taking part in a larger study of substance use, and all had brain scans at three points over four years. Three-quarters were men, and nearly all were white.


While their brain was being scanned in a functional MRI scanner, they played a game that asked them to click a button when they saw a target on a screen in front of them. Before each round, they were told they might win 20 cents, or $5—or that they might lose that amount or have no reward or loss.


The researchers were most interested at what happened in the reward centers of the volunteers' brains—the area called the nucleus accumbens. And the moment they cared most about was that moment of anticipation, when the volunteers knew they might win some money, and were anticipating performing the simple task that it would take to win.


In that moment of anticipating a reward, the cells of the nucleus accumbens usually swing into action, pumping out a 'pleasure chemical' called dopamine. The bigger the response, the more pleasure or thrill a person feels—and the more likely they'll be to repeat the behavior later.


But the more marijuana use a volunteer reported, the smaller the response in their nucleus accumbens over time, the researchers found.


While the researchers did not look at the volunteers' responses to marijuana-related cues, other research has shown that the brains of people who use a high-inducing drug repeatedly often respond more strongly when they're shown cues related to that drug. The increased response means the drug has become associated in their brains with positive, rewarding feelings. And that can make it harder to stop seeking out the drug and using it.


If this is true with marijuana users, "it may be that the brain can drive marijuana use, and that the use of marijuana can also affect the brain. We're still unable to disentangle the cause and effect in the brain's reward system, but studies like this can help that understanding," said first author Meghan Martz, U-M doctoral student in developmental psychology,


Regardless, the new findings show that there is change in the reward system over time with marijuana use. Heitzeg and her colleagues also showed recently in a paper in Developmental Cognitive Neuroscience that marijuana use impacts emotional functioning.


The new data on response to potentially winning money may also be further evidence that long-term marijuana use dampens a person's emotional response—something scientists call anhedonia.


"We are all born with an innate drive to engage in behaviors that feel rewarding and give us pleasure," said co-author Elisa Trucco, psychologist at the Center for Children and Families at Florida International University. "We now have convincing evidence that regular marijuana use impacts the brain's natural response to these rewards. In the long run, this is likely to put these individuals at risk for addiction."


Marijuana's reputation as a "safe" drug, and one that an increasing number of states are legalizing for small-scale recreational use, means that many young people are trying it—as many as a third of college-age people report using it in the past year.


But Heitzeg says that her team's findings, and work by other addiction researchers, has shown that it can cause problems with emotional functioning, academic problems and even structural brain changes. And, the earlier in life someone tries marijuana, the faster their transition to becoming dependent on the drug, or other substances.


"Some people may believe that marijuana is not addictive or that it's 'better' than other drugs that can cause dependence," Heitzeg said. "But this study provides evidence that it's affecting the brain in a way that may make it more difficult to stop using it. It changes your brain in a way that may change your behavior, and where you get your sense of reward from."


She is among the neuroscientists and psychologists leading a nationwide study called ABCD, for Adolescent Brain Cognitive Development. That study will track thousands of today's pre-teens nationwide over 10 years, looking at many aspects of their health and functioning, including brain development via brain scans. Since some of the teens in the study are likely to use marijuana, the study will provide a better chance of seeing what happens over time.


In addition to Heitzeg, Martz and Trucco, the study's authors include Lora Cope, Jillian Hardee, Jennifer Jester and Robert Zucker. The study was funded by the National Institutes of Health.

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What a pisss poor study.


 I think they proved that marijuana makes you less greedy?  Then they somehow jump to other drugs and what they do and admit it has nothing to do with marijuana...


While the researchers did not look at the volunteers' responses to marijuana-related cues, other research has shown that the brains of people who use a high-inducing drug repeatedly often respond more strongly when they're shown cues related to that drug. The increased response means the drug has become associated in their brains with positive, rewarding feelings. And that can make it harder to stop seeking out the drug and using it.


If this is true with marijuana users,



Sheesh.  So.. marijuana evens out your reward response to money.  Heh.

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As if money is the only reward worth pursuing in life.


So if you want to create money grubbing little Donald Trumps, do not let young minds try cannabis.


If you want to create customers for casinos, oppose cannabis.


If you want people to buy into the fantasy of capitalism, oppose cannabis.

Edited by AmishRnot4ganja

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 Anybody familiar with an MRI could imagine the ridiculousness of this test. Anybody not that familiar: here is an overview.  ...Imagine being strapped onto a sliding table that travels inside of huge donut about 4 ft in diameter yet the center is apx 24", with an IV stuck in your arm along with the requisite hoses. Along with ear plugs... Imagine too that in one hand you have a button to call for help and according to them another button to play a game where they might win 20¢. All this being overshadowed by the fairly loud clicking, buzzing, whirring of this quite intimidating machine while you are being given instructions by someone in another room (presumably for their own protection) to, "breath", "take a deep breath", "now hold your breath", ...sometimes for what seems like 30 seconds. Then finally, "OK breathe".  Unless their is some other dire need for a 20 yo to be undergoing this procedure, I would not  advise it. Not for 20¢, $5.00 or $50.00. ...$500.00, well...    



     Dunkin Donut...gallery_2767_621_8893.jpg





  Ironically, in light of Ann Arbors' reputation, my experience with Cannabis and the U of M hospital is that they are not very MJ friendly at all. Nor did they impress me with their knowledge or expertise of this remarkable herb.  Even when asked to substitute an MJ derivative: Marinol for an opiod (ie: Norcos) including outright swapping after a major surgery, I heard every reason they have from they wouldn't/couldn't substitute one 'narcotic' for another to now your Cancer free and you can't have MJ anymore, yet that was not my qualifying condition, my QC was Hep-C. They would NOT  condone or prescribe any form of Cannabis for me.   Notwithstanding this was late 2009 , I was a carded Medical Cannabis patient and Cannabis was listed at the top of my Medication Chart.

Edited by solabeirtan

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Reading the study:


use http://sci-hub.cc/


They didnt post the controls info at all. I really wonder why they didnt post control races/ages/drinking habits? Also how did they even publish without that info? darn, cannot access the supplimental material without a login.


Self report of everything


Given the high incidence of polysubstance use 41 and the

fact that all drugs of abuse affect dopamine levels in the

NAcc, 13-15 we accounted for potentially confounding sub-

stance use. For example, there is evidence 52,53 that heavy al-

cohol use may blunt NAcc activation to reward anticipation.

We found an effect of long-term marijuana use on anticipa-

tory reward processing when controlling for potential effects

of previous and concurrent binge drinking. Thus, marijuana

use may have a specific influence on NAcc response beyond

that of heavy alcohol use.

People get paid to write bunny muffin like this.


One limitation of our study is that the binge drinking thresh-

old was 5 or more standard alcoholic drinks for both men and

women, which is greater than the typical cutoff of 4 or more

drinks for women. 54 Our findings also may have limited gen-

eralizability,given that the sample consisted predominately of

white and high-risk (defined by family history of SUD) young


Testing positive for marijuana use but reporting ab-

stinence within 48 hours before each scan did not greatly affect

the findings (eResults in the Supplement).

they do not mention anywhere in the study that they tested people for marijuana use besides that sentence.

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Bah, more bunk 'science'. 


Like Sola stated, having an MRI, especially the first time is a bit intimidating, uncomfortable, loud et al.

I've had several and now request an "open MRI" which is a much nicer experience.


I am just going to speculate here and suggest that the first "rush" of reward is an emotional response which is governed by the

Amygdala (fight or flight/ knee jerk), and many people will respond and react upon that first rush in an irrational manner.

Cannabis might be one key to a pause of sorts (chillin) that allows the mind to tap into the 'thinking' (wise) part of our brains which

balances the reactionary (fight or flight) part of our brain which in turn leads us to a more reasonable response?

It gives the cannabis user the opportunity to choose their reaction... maybe?




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I guess only money grabbing, lunchtime martini sucking sob's with a narcissist personality that believes money is God are the only ones that are deemed successful in our "new society". If you happen to find other things in life that are much more satisfying than working all the time to "get ahead", you are a failure. If you would rather spend time with your family going camping instead of running each and every weekend to so many school sanctioned activities that all require oodles of money for equipment, driving miles to and from, you are a failure. If you like to smoke a fatty, sit on your porch and watch the sunset instead of mowing your 15 acre manicured estate, you, sir or madam, are a failure!!! I am not what one would call religious, but I do just love one of Jesus' parables: For it is easier to thread a camel through the eye of a needle than it is for a rich man to enter the kingdom of heaven. Most religions teach the horrors of loving money!!! Just a rant from a sunset watching old fool :>)

                                          Farmer Brown

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Yea I don’t quite get this. They run the test using an addictive behavior (gambling), which cannabis users supposedly become less interested in. But because they don’t want to participate in other addictive, reward driven behavior they are more prone to addiction? This seems like flawed logic, because they assume that cannabis users would need another outlet to achieve satisfaction. Yet, it seems that they would be just fine with that outlet being cannabis rather than something more damaging like gambling addiction.


It has been shown that marijuana is much less addicting than other common drugs including tobacco and alcohol; I believe the ‘addiction rate’ was somewhere around 7% (versus 20-35% of other drugs). We also know that powerful opioids can completely rewire the brain’s reward center in a matter of weeks. Why not include a comparison to other drugs so we can really see what the problem is in this country. People become addicted to everything; relationships, food, ect. The issue is how these addictions affect your health, social factors, ect. Yea, cannabis can affect these issues, but it is primarily due to the judicial system ruining lives... not the drug itself.


This has also been done before and previously refuted, but realistically the sample size of these studies is too small: http://www.tokeofthetown.com/2011/06/study_claims_marijuana_users_dont_care_if_they_los.php

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Nice test!


I learned cannabis cures gambling addiction symptoms!

Cannabis users are less likely to rob you of your valuables!

Cannabis using bosses are better to work for!

Cannabis using females are likely not after your money!

Cannabis users are not fooled by the minimum wage follies of recent!

Cannabis users are more charitable!



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And this, folks, is apparently at the root of all opposition to cannabis!


Cannabis makes people have more empathy. Cannabis users don't care about climbing the social ladder via stabbing their competition in the back so that they can climb over them on their way to "The Top". Caring about others is apparently a bad attribute in the eyes of the "Cannaphobic" ones.

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I am interested in the control group.  I mean, come on man, how excited do people get to win up to $5.  And even if you did get "a little rush", how many times are you going to get that "rush" at three different points over a four year period??


I would sort of think any rush you got about $5 might diminish over time.  How could you not monitor and publish the results of a control group?

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Very poorly run test and a very poorly written article. Would it be better to test people who need MMJ for pain over other people stoned and addicted to opiates?

That should be the next test, take away peoples pain pills and watch them squirm. People are DYING from opiates abuse and people are actually wasting time/resources test marijuana?

What a waste. Next thing they'll tell me is the jails overcrowding has nothing to do with marijuana convictions.


The last time I had am MRI at U of M, my insurance sent me a statement saying it paid over $4500 for it. So to give away multiple MRIs to people who don't need them? A total waste of time/money. You would be better off taking that time and money and feeding/housing the homeless living under a bridge right there in Ann Arbor. But studies now prove that NOT using cannabis makes people more insensitive to others suffering. And it proves people NOT using marijuana are more selfish and greedy the people who do.



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Here we have it; marijuana may be useful in treating drug and other addictions, contradicting their simultaneous claims it might lead to other addictions:


We did not observe an association between NAcc response to monetary reward and later marijuana use. Although a direct robust association may not exist between these factors, repeated use may result in a bias toward marijuana and marijuana-associated cues relative to unrelated cues.


Relative risk of becoming addicted:

32% Tobacco
23% Heroin
17% Cocaine
15% Alcohol
9% Cannabis


Yea… I think there is a problem with their methods or controls.


When the cross-lagged model was tested with the inclusion of previous and concurrent cigarette use, the effect of marijuana use from time 2 to time 3 remained significant (β =−0.29; P = .005) and the effect of cigarette use was nonsignificant.


So the drug that is at least 4x more addictive than cannabis (tobacco) had an insignificant effect? Really? That’s bizarre… No I think they were just not able to control for additional factors properly including tobacco use. P = 0.005 is also not that significant, typically they go for P = <0.001 when claiming results.

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