Excessive Cannabis Smoking Reduces Dopamine Levels, Study Finds

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Researchers at Columbia University Medical Center, New York, have discovered that heavy cannabis use has the same effect on your brain’s dopamine system as chronic cocaine or heroin use: i.e. excessive smoking of cannabis, just like cocaine and heroin addiction, decreases dopamine levels in the brain and could lead to memory, attention, and problem-solving deficits.

In the study, titled “Deficits in Striatal Dopamine Release in Cannabis Dependence,” published online on March 22 in Molecular Psychiatry, an international team of researchers used positron emission tomography (PET) to track a radiolabeled molecule that binds to dopamine receptors in the brain to measure dopamine release in the striatum and its subregions, as well as in several brain regions outside the striatum, including the thalamus, midbrain, and globus pallidus.

The PET scans found that the cannabis users had significantly lower dopamine release in the striatum, including subregions involved in associative and sensorimotor learning, and in the globus pallidus. The authors stated:

“Most drugs of abuse lead to a general blunting of dopamine release in the chronic phase of dependence, which contributes to poor outcome. To test whether cannabis dependence is associated with a similar dopaminergic deficit, we examined striatal and extrastriatal dopamine release in severely cannabis-dependent participants, free of any comorbid conditions, including nicotine use… In conclusion, this study provides evidence that severe cannabis dependence—without the confounds of any comorbidity—is associated with a deficit in striatal dopamine release. This deficit extends to other extrastriatal areas and predicts subclinical psychopathology.”

However, the researchers also noted that the result does not indicate that excessive smoking of marijuana directly caused the participants’ decreased dopamine levels; other pre-existing health conditions could have also contributed to the findings, they added. Lead author Dr. Anissa Abi-Dargham, professor of psychiatry (in radiology) at Columbia University Medical Center, explained:

“We don’t know whether decreased dopamine was a preexisting condition or the result of heavy cannabis use, but the bottom line is that long-term, heavy cannabis use may impair the dopaminergic system, which could have a variety of negative effects on learning and behavior… In light of the more widespread acceptance and use of marijuana, especially by young people, we believe it is important to look more closely at the potentially addictive effects of cannabis on key regions of the brain.”

According to Clinical Psychologist Dr. Joseph Carver, low levels of dopamine in the brain can produce motor-control problems; lead to Parkinson’s disease, depression and anxiety; and affect the portions of the brain that impact thinking, impairing the ability to concentrate and focus.

In 2013, scientists at Imperial College London, University College London and King’s College London conducted the PET scans on the brains of 38 people – 19 regular cannabis users and 19 non-users – and found low dopamine levels in chronic cannabis users. Dr Michael Bloomfield of Imperial College London, noted:

“Dopamine is involved in telling the brain when something exciting is about to happen – be it sex, drugs or rock ‘n roll. Our findings explain why cannabis has a tendency to make people sit around doing nothing. The results weren’t what we expected but tie in with previous research on addiction which has found substance abusers have altered dopamine systems.

“Although we only looked at cannabis users who have had psychotic-like experiences while using the drug, we think the findings would apply to cannabis users in general since we didn’t see a stronger effect in the subjects who have more psychotic-like symptoms.  It could also explain the “amotivational syndrome” which has been described in cannabis users but whether such a syndrome exists is controversial.”

In 2015, the US National Cancer Institute admitted that marijuana kills cancer cells; however, excess of everything is bad, and cannabis – a non-toxic substance – is no exception. What do you think? Please share your thoughts in the comment section below.


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26 COMMENTS

  1. This study is an excellent reason to keep arresting adults for cannabis. Of course, the only money for cannabis research MUST have the reefer madness outcome implicit in it. Cannabis has only been used for a thousand years, and our streets and alleys are full of dopamine depleted cannabis dependent junkies, lolling in the gutter.

    • +your a complete idiot!!!! you deserve to be arrested simply because you choose to do something half of society thinks is harmful to yourself and only yourself and the other half thinks it has benefits from its use. Reason you before any pot smoker deserves to be arrested BY A PERSON SMOKING POT OR ANY OTHER KNOWN OR UNKNOWN DRUG IF IT EVEN HURT THEM THE ONLY FUCKING PERSON THERE HURTING IS THEMSELVES FUCKTARD!!! But lets support and promote doctors writing prescriptions to millions of people a day that kill thousands and thousands of people each and every year. Hell at least there only hurting everyone besides themselves so praise that GOD like doctor over there why dont you ignorant fuck stick!!!

    • A thousand years?
      You obviously do not know your history, cannabis has been recorded since 2737 BC when Chinese emperor Shen Yung noted it’s powers as a medication for rheumatism, gout, malaria, and oddly enough, absent-mindedness.
      You must have the last one, I smoke everyday damn day and I’m not a junkie I get my shit done. Quit stereotyping.

  2. Can a link to the actual scientific study be provided? Otherwise this is just a compilation of opinion videos and snippets from opinionated articles. I want to see the time tables, the control group, the variable group, and I want to see repeated trials. Otherwise, this is meaningless “Don’t do drugs,” to me.

      • Clearly you do not know the science behind Cannabis, it contains 21 different amino acids along with the 8 essential ones. We also have a system in the brain known as the “Endocannabinoid system,” it has “CB1″(associated with the central nervous system) and “CB2″(associated with the immune system) receptors. Since we have this system inside our head, it seems to imply that we were made to handle Cannabis…and also, smoking is the result of man-made extensions, eating Cannabis on a daily basis will provide you with good health. It is a plant after all, so let’s treat it like one…

    • ” “Deficits in striatal dopamine release in cannabis dependence,” was published online on March 22, 2016, in Molecular Psychiatry. Authors are Elsmarieke van de Giessen, MD, PhD, Jodi J. Weinstein, MD, Clifford M. Cassidy, PhD, Margaret Haney, PhD, Zhengchao Dong, PhD, Rassil Ghazzaoui, MA, Najate Ojeil, MA, Lawrence S. Kegeles, MD, PhD, Xiaoyan Xu, PhD, Nehal P. Vadhan, PhD, Nora D. Volkow, MD, Mark Slifstein, PhD, and Anissa Abi-Dargham, MD. Affiliations are: Department of Psychiatry, Columbia University Medical Center and New York State Psychiatric Institute, New York NY (EvdG, JJW, CMC, MH, ZD, RG, NO, LSK, XX, NPV, MS, AA); Department of Nuclear Medicine, Academic Medical Center, Amsterdam, The Netherlands (EvdG); Department of Psychiatry, Stony Brook University School of Medicine, New York, NY (NPV); National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD, (NV).”

      I didn’t look at it, just copied from the link provided

      I strongly suspect that the substances noted reduce dopamine production because it is not needed at the same levels with the other substances present, or that, as noted in the article, the lower dopamine levels are congenital and possibly associated with divergent thought conditions.

      Note the use of subjects with psychotic episodes. Turns out that people with genetic variants associated with ADD/ADHD, schizophrenia, bipolar or major depression, and the autistic spectrum have a predisposition, or natural affinity for the herb, so any study of cannabis users will have a greater number of those affected, particularly if they use only those who demonstrate symptoms. So, not the weed.

  3. Again, its the similar kind of study done multiple times.

    There are two groups, one of which is labeled a “heavy cannabis user” group and a control group.

    I’m not saying this happened in this particular study, but several which I’ve read, have had the “heavy cannabis users” as a group who also have more smoking, more drinking and their own psych evaluations of their mental health was poorer.
    So in essence a group of poor people who use drugs versus well-off people who don’t.

    In that case its not cannabis. Its something else that cannabis alleviates, and which was pre-existing.
    One study found that a cannabis user has less gray matter, which has a lot of CB-receptors. They concluded that cannabis had diminished the amount of grey matter.
    But how could they know?
    Maybe those areas with those receptors are, lets say, in charge of some societal mechanic in humans. Let us then assume a child, who doesn’t get to act those mechanism in his early life and therefore never develops those areas. Maybe that child will later in life come across cannabis and find it alleviates the pain he has had for such a long time. Maybe he gets a bit addicted on it as well.

    I’m not saying the studies are wrong, I’m saying the conclusions might be.

    One study done on twins didn’t really find much differences between the twins, even if one smoked.

  4. Have anyone stopped to consider that the study can be staged for a knd of a anti canabis propaganda, as a lot of things are by the people who banned canabis in the first place and people who own healthcare, people who created illnesses etc. lately we see the world going towards eastern methods of cureing cancer , hiv and many more illneses maybe thats the reason of all these anti canabis articles and studies

  5. “However, the researchers also noted that the result does not indicate that excessive smoking of marijuana directly caused the participants’ decreased dopamine levels; other pre-existing health conditions could have also contributed to the findings, they added.

    “…..however, excess of everything is bad, and cannabis – a non-toxic substance – is no exception.”

    I really wish misleading articles like this would cease being regurgitated online, especially opinion-driven drivel like this should be taken down so as to not confuse the idiots of the internet that take this as factual and share it en mass.

    Anonymous, you should know better; shame on you!

    • I agree.

      This study did not show that smoking cannabis REDUCES dopamine levels. It showed that those who smoke a lot have low dopamine levels. That’s an entirely different thing.

      I’ve looked through these studies multiple times and there is never a certain causality.
      For instance one study which had a group called “heavy cannabis user” and “control”. The first group used way more alcohol and tobacco than the second and rated their self-esteem low and ADD high. The second group did not.
      So what in fact happened was that the researchers took a group of people from the downside of life who happened to smoke and compared them to healthy and rich people who don’t.

      One could draw conclusions from that very study that cannabis causes low self-esteem or that cannabis causes alcoholism or that it causes poverty.
      CORRELATION ISN’T CAUSATION.

      Those people might have naturally very low dopamine levels and they can’t get enjoyment out of anything, maybe even due to a societal factor (society is shit, get existential crisis, can’t enjoy anything) and the only thing that even remotely feels like helping, is smoking cannabis.
      You can’t find things like these in a PET-scan.

      One would have to survey people from all sorts of places from society, and from each place persons who have smoked and who haven’t, and make others start smoking during the study and have some quit during the study.

      SO much non-scientifical shit.

      SHAME ON YOU ANONYMOUS.

  6. There’s holes in this study. And has been done by an agency that is biased towards drugs that aren’t approved by big pharma and the government. There’s more research to be done before people can go pointing the finger saying it’s bad. Just like they should be doing with some of these medications that hit markets too early and kill people. Marijuana still hasn’t killed anyone, how about that?

  7. There’s holes in this study. And has been done by an agency that is biased towards drugs that aren’t approved by big pharma and the government. There’s more research to be done before people can go pointing the finger saying it’s bad. Just like they should be doing with some of these medications that hit markets too early and kill people. Marijuana still hasn’t killed anyone, how about that?

  8. “Although we only looked at cannabis users who have had psychotic-like experiences while using the drug, we think the findings would apply to cannabis users in general… ”

    yeah you know, because only looking at a very specific sub-set of any grouping of people is clearly broad enough of scope to accurately make definitive statements about the entire group…

  9. Sorry, however please don’t call it marijuana…. That is a derogative term to the “miracle plant.” It is either Cannabis or Hemp! It is clear that they performed an experiment that I would find hard to believe the outcome of without definitive proof,However I`m only posting to ask you to use the proper name for which you speak!

    Thank you and may the “herb of life” grant you eternal peace and happiness.

  10. Nice pick up andy.ec. ^

    I would also have to agree to disagree with the credibility of Dr Michael Bloomfield’s research methods.

  11. Should do a study on ex-heavy cannibis users. This is like measuring peoples serotonin levels they day after they take exstacy.

    love this part
    “Funding for this study was provided by the National Institute on Drug Abuse”

  12. looks like anonymous has smoked to much weed. this information is i dont know how many decades old. 1970’s called they want there research back. fucking loosers get off your ass and actually do something besides copy and paste

  13. “…but the bottom line is that long-term, heavy cannabis use may impair the dopaminergic system, which could have a variety of negative effects on learning and behavior”

    We have a longitudinal study that demonstrates, not so much.

    The Meier study of the Dunedin cohort suggested an 8 point drop in IQ scores for heavy long term cannabis smokers, though following work demonstrated that the losses could be from socio economic factors. If you examine the subtest scores though, an interesting fact emerges. The 3% of users who lost the, up to 8 points overall, scored higher in the Arithmetic, Block diagram, and Picture completion subtests, while the non-users scored lower in these three subtests.

    Again, noting the natural affinity for the herb demonstrated by folks with divergent thought conditions, we should expect a loss in social functions and an increase in analytical abilities from this group, whether they used cannabis or not.

    Dr. Meier has since reexamined data, and found that cannabis users have a greater incidence of gum disease. But that and the other are as easily attributed to living with a baseless prohibition that excludes one from society for seeking out relief.

  14. A study which use 11 dependent persons – probably with social problems, so maybe already bout of depression, – to conclude that excessive cannabis smoking reduces dopamine levels…

    This isn’t serious. Did these scientists took care about an eventually confusion factor? I don’t guess.

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