Heavy Cannabis Use Associated With Reduced Dopamine Release

In a recent study, researchers found evidence of a compromised dopamine system in heavy users of marijuana. Lower dopamine release was found in the striatum – a region of the brain that is involved in working memory, impulsive behavior, and attention. Previous studies have shown that addiction to other drugs of abuse, such as cocaine and heroin, have similar effects on dopamine release, but such evidence for cannabis was missing until now.

“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,” said Anissa Abi-Dargham, MD, professor of psychiatry (in radiology) at Columbia University Medical Center (CUMC) and a lead author of the paper.

The study included 11 adults between the ages of 21 and 40 who were severely dependent on cannabis and 12 matched healthy controls. On average, the cannabis group started using at age 16, became dependent on cannabis by age 20, and have been dependent for the past 7 years. In the month prior to the study, nearly all users in this study smoked marijuana daily.

Image shows the location of the striatum.
Compared with the controls, the cannabis users had significantly lower dopamine release in the striatum, including subregions involved in associative and sensorimotor learning, and in the globus pallidus. Image is for illustrative purposes only.

Using positron emission tomography (PET) to track a radiolabelled molecule that binds to dopamine receptors in the brain, the scientists measured 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 cannabis users in this study stayed in the hospital for a week of abstinence to ensure that the PET scans were not measuring the acute effects of the drug. Participants were scanned before and after being given oral amphetamine to elicit dopamine release. The percent change in the binding of the radiotracer was taken as an indicator of capacity for dopamine release.

Compared with the controls, 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 investigators also explored the relationship between dopamine release in a key area of the striatum and cognitive performance on learning and working memory tasks. Although there was no difference between groups in task performance, in all participants lower dopamine release was associated with worse performance on both tasks.

“We don’t know whether decreased dopamine was a preexisting condition or the result of heavy cannabis use,” said Dr. Abi-Dargham. “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.”

Jeffrey Lieberman, MD, Chair of Psychiatry at CUMC and past president of the American Psychiatric Association, noted that “these findings add to the growing body of research demonstrating the potentially adverse effects of cannabis, particularly in youth, at the same time that government policies and laws are increasing access and use.”

About this neuroscience research

“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).

Dr. Haney has received partial salary support for investigator-initiated studies from Insys Therapeutics Inc and Lifeloc Technologies and has served as a consultant to Aelis Farma and Health Advances LLC. Dr. Kegeles has received research support from Amgen. Dr. Slifstein has received research support from Forest Laboratories, PierreFabre, CHDI, and Otsuka and has provided consultation for Amgen. Dr. Abi-Dargham has received research support from Takeda and Forest Pharmaceuticals and has served on advisory boards for Roche, Forum, and Otsuka. The remaining authors declare no conflict of interests.

Funding: Funding for this study was provided by grant R01 DA022455-01A1 from the National Institute on Drug Abuse to Dr. Abi-Dargham. Dr. van de Giessen was supported by a Rubicon grant from the Netherlands Organisation for Scientific Research (825.12.009).

Source: Rachel Yarmolinsky – Columbia University Medical Center
Image Credit: The image is in the public domain.
Original Research: Abstract for “Deficits in striatal dopamine release in cannabis dependence” by E van de Giessen, J J Weinstein, C M Cassidy, M Haney, Z Dong, R Ghazzaoui, N Ojeil, L S Kegeles, X Xu, N P Vadhan, N D Volkow, M Slifstein and A Abi-Dargham in Molecular Psychiatry. Published online March 22 2016 doi:10.1038/mp.2016.21


Abstract

Deficits in striatal dopamine release in cannabis dependence

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 (CD), free of any comorbid conditions, including nicotine use. Eleven CD and 12 healthy controls (HC) completed two positron emission tomography scans with [11C]-(+)-PHNO, before and after oral administration of d-amphetamine. CD stayed inpatient for 5–7 days prior to the scans to standardize abstinence. Magnetic resonance spectroscopy (MRS) measures of glutamate in the striatum and hippocampus were obtained in the same subjects. Percent change in [11C]-(+)-PHNO-binding potential (ΔBPND) was compared between groups and correlations with MRS glutamate, subclinical psychopathological and neurocognitive parameters were examined. CD had significantly lower ΔBPND in the striatum (P=0.002, effect size (ES)=1.48), including the associative striatum (P=0.003, ES=1.39), sensorimotor striatum (P=0.003, ES=1.41) and the pallidus (P=0.012, ES=1.16). Lower dopamine release in the associative striatum correlated with inattention and negative symptoms in CD, and with poorer working memory and probabilistic category learning performance in both CD and HC. No relationships to MRS glutamate and amphetamine-induced subclinical positive symptoms were detected. 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.

“Deficits in striatal dopamine release in cannabis dependence” by E van de Giessen, J J Weinstein, C M Cassidy, M Haney, Z Dong, R Ghazzaoui, N Ojeil, L S Kegeles, X Xu, N P Vadhan, N D Volkow, M Slifstein and A Abi-Dargham in Molecular Psychiatry. Published online March 22 2016 doi:10.1038/mp.2016.21

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  1. Research funded by an organization that would cease to exist (…. meaning no $$$ for more research…) if drug addiction becomes accepted as a medical problem and not a law enforcement problem. It was inevitable that the results came back as scary anti-cannabis.

  2. So what is the consequence of reduced dopamine? Worse performance on learning and working memory tasks? hmm….I can live with that. Very strong emphasis on “I”
    The big Oil & Gas producer I do engineering for might not appreciate my learning and working memory task disability I developed due to very heavy use in college.

  3. This is Good News for compulsive gamblers! Since the same scientific community that spawned this study has also stated that excessive dopamine(produced when we win making us feel good) causes the desire to continue gambling when losing. Hereafter, everyone with a gambling problem should light up before entering the casino!
    The only question one has to ask when reading about all of these “studies” is, “Where are all the casualties? Marijuana has been used for hundreds of years and there simply is no correlation between the studies that warn of harmful side effects and the real world experience of hundreds of thousands of individuals who have been safely using cannabis for decades!

  4. Going by this article, it would seem that marijuana would help people with such disorders as bi-polar disorder.

  5. do some reserch on Hydrocodone,methadone,oxycotin others you fools legalized that do more harm than marijuana,

  6. if BIG IF very heavy weed use (how was it measured to be heavy?) in fact lowers impulse control wouldn’t the impulse to use other drugs be nullified and if by their study it’s nullified why do they use harder drugs? Then you must also ask if they had test subjects for this “study” are you saying it was or was not a controlled study an uncontrolled study would be invalid at the start so it’s controlled meaning they supplied weed, meth, coke etc so they created addicts? again invalid study This seems more of a “study” to force “big weed” like cigarettes and alcohol instead of small business. Weed doesn’t make you lazy you being lazy is the issue. I do believe smoking (combustion) is bad for you vaping(no fire) and eating are much healthier for you. Lab coats and suits have been know to create IISC (imaginary intelligence and superiority complex) imagine if I never smoked mmj I would never have been a combat vet with 2 BS 1Ph’d and a daily life I would have been…………..Einstein’s over achieving superior.

  7. I find it interesting that they choose not to describe what constitutes “heavy use”. Clearly any drug which induces changes in mood must alter the brain chemistry as that is what controls mood. It is also unclear how long the condition persists for when a “heavy user” stops using. A heavy drinker also suffers physiological and mental effects which are long lasting and detrimental yet those who have a couple of beers on weekends seem not to suffer ill effects.
    Clearly this is research with a political goal; more junk science.

  8. A meaningful point is being missed by critics of this article; impaired time loss. Diminished functioning in a competitive
    world that requires optimal functioning in a developing brain and for social development during which cognitive steps should not be missed. Why are you splitting hairs? Why the equivalency head games? Why the straw man arguments? How about some intellectual maturity, please.

  9. How come none ever discuss the fact that the prime causes of traumatic stress – physical and sexual assaults, rape, child abuse, robberies, etc. – are crimes committed by the millions reported (most are not) a year? In my lifetime (49 years) America has been adding every single year, year in an year out, more people traumatized by violent crimes committed by one using the drug of choice of the scientist, the doctor, the lawmaker, the judge, the teach, and the cop – alcohol – than are born healthy into the population.

    The surgeon general has warned of an epidemic of stress. The military (alcoholic to the core) is suffering a PTSD “epidemic.” The prime cause of PTSD in the US is not combat, though, but those millions of alcohol-related crimes. There are over 40 million raped or sexually assaulted women alone, many of them limping and crawling through life.

    And the alcoholics are worried what cannabis – the drug of choice of those 10’s of millions suffering traumatic stress – might or could do to the brain.

    Good grief! The Body of America is alcoholic to the core, traumatizing more children every year from an alcohol-related crime than are being born healthy every year, and the “experts” and “professionals” are worried about cannabis – a freaking pinhole in the hill of a ship. Meanwhile, while the captain and the crew are getting drunk on a drug already proven to add more stress into the system, and deficit, than any “recreational” benefit it might have had, (scientifically there is now none) are allowing water in through the gouge caused by the iceberg, alcohol.

    Get a grip, alcoholics.

  10. The study was brought to you by the US Government:

    “The National Institute on Drug Abuse is a United States federal-government research institute whose mission is to “lead the Nation in bringing the power of science to bear on drug abuse and addiction.”

    Another paid hit job on Cannabis by the US Government.

  11. Daily (after work) user since 1975, married at 21 (coming upon 34 years), full time employee for 35 years (never fired from any of my 9 jobs through these years), have 4 normal and productive in society children, 6 normal grand-children and have enjoyed life always. In fact I just retired as of today and intend to continue to spend the rest of my relaxed life enjoying my remaining years with my grand-children (and possibly great grand-children) along with my wife. Note: My wife hasn’t smoked (anything) since her first missed period leading to the birth of our first child and did not start smoking again until after the birth of our last child, and I’ve never smoked tobacco nor have I ever smoked marijuana before or during work. I haven’t looked up what dopamine is yet but I have always enjoyed my life.

    1. I just Googled dopamine and according to Wiki as best as I can understand it, I must still be getting dopamine “rewards” from the inhalation of cannabis! Now if I really felt like throwing my money away, I’d (P.E.T.) my brain daily for a couple of months.

  12. All this study means to me is, the more you smoke marijuana, the more you’ll become tolerant to it. And, if you smoke before going to class at school, you are more likely able to filter through the bs that is taught to you and are able to gain more honest information from it. The author of this piece very obviously has a limited amount of exposure to marijuana.

  13. I could guarantee the following comments from proponents of this research may be living “comfortable” lives, but they are not where they want to be. Most likely associated w/ marijuana usage.

    We get it. It’s safer than alcohol, crack, meth, crank, cocaine, LSD, even prescription medicine…..you name it. It’s safer…right? that’s the justification from these self proclaimed “potheads”.

    But the key to moderation is moderation itself. Sure, go ahead and use marijuana. Nobody is stopping you. This is just a research to tell you what it does in the long term. But beware that heavy use can alter the affect of your lives.

    In my professional career, potheads are mostly people in dead end professions. I have never met a Business exec, Doctor, Lawyer, or anyone with an elite profession to be potheads or even have dabbled in it.

    I’m just saying.

  14. “We don’t know whether decreased dopamine was a preexisting condition or the result of heavy cannabis use,” said Dr. Abi-Dargham. “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.”

    Huh?

    Well which is it?

    Do you know or don’t you?

    Just like the majority of the negative NIDA-funded studies if you actually read them.

    There’s always a very similar disclaimer. Read the studies.

    How much longer do we have to endure these NIDA-funded studies with a mandated prejudice to research and find only the negative effects of cannabis use and not the medicinal benefits or any other positive effects.

    This is yet another “we don’t know study but we are absolutely certain (somehow) that it just has to bad for you, it just has to be, we just know it” so an article can be written and placed in the media with a sensational, provocative misleading headline so as to sway public opinion without any real fact based evidence.

    Arrgghhh!

  15. So, Steve Jobs was a heavy smoker, so explain that one. Most geniuses are/were smokers.

  16. Funding: Funding for this study was provided by grant R01 DA022455-01A1 from the National Institute on Drug Abuse to Dr. Abi-Dargham. Dr. van de Giessen was supported by a Rubicon grant from the Netherlands Organization for Scientific Research (825.12.009).

    No one believes the propaganda.

  17. Yeah whatever, I was prescribed pain medication for 10 years and when I got off of that they put me on another Rx, suboxone, and that I think was worse than the pain meds and made me sick as hell for over a month when I took myself off of that poison. The only thing that has helped is cannabis. I don’t feel bad anymore nor do I crave it when I don’t have any. I went through all of this while working 60 hours a week.

  18. There’s one really obvious problem with this study, which isn’t sample size or any of the typical complaints. These are “severely cannabis-dependent participants” who were tested after a week of abstinence. In other words, they were tested while in a state of drug withdrawal. Obviously an addict going through withdrawal is going to perform poorly on cognitive tests; they’re sick! If this test had been done a month or two after quitting, (I’d give it quite a bit of time, due to Cannabis’ immense half life) it would make sense to be concerned. As it stands, this study says nothing, except that people going through drug withdrawal have impaired cognition. Duh.

  19. Just to be sure, the study looked at “Heavy” users of marijuana and not light or moderate users. As it turns out alcohol, nicotine, and gluttony are also known to reduce D2 receptor quantity. I would be curious to see how the researchers compensated for the munchies in their study or if they simply chose to ignore other stimuli.

  20. …so this study was done on how many people? …11 Hmm. I started smoking in 1976 (12 yo) and was smoking daily by 1982 (18 yo) I earned my BS in 1987 and have be working in the EE field for the same company since 1988. I still smoke daily. I agree with Vic, weed is not for everyone. …but reporting on an 11 person study?

  21. “We don’t know whether decreased dopamine was a preexisting condition or the result of heavy cannabis use,” said Dr. Abi-Dargham…. So, why publish an article then?

  22. Let’s say that the research is screwed up because of the introduction of the amphetamines…how stupid is that to add meth to the mix to create a standard…how does the meth amphetamines affect the study, how long does it stay in the brain? All the people I’ve seen on meth have not just been affected for a week, but months. Your research is bad. Why do you have to stimulate the Dopamine and cloud the issue of Marijuana use with mixing other harmful poisons that kill people. You should have to return the grant moneys and do an honest study. Marijuana has been around since 2747BC no deaths, no deaths…how about meth and the other medicines that are provided to human beings. Bad study, bad scientists, what crap! Get more funding to support your BS studies. You need your licenses yanked…yesterday!

    1. They need to explain why geniuses like Steve Jobs and many, many others are/were serious users. Most geniuses have always experimented with ganja and street drugs. When you are a genius, you search other higher levels of consciousness, thus the ganja, and other experiences.

    2. These people are so transparent. Drug war hysteria and exaggerations. They have an agenda period. I,m 61 and know many people that have smoked marijuana their whole lives no differently than a typical occasional drinker of alcohol. All the way back to high school and some of us were national honor society. A few of them were heavy smokers years ago. Everyone is doing fine. And the old “young people” point is crap for the most part. Legalizing marijuana has no effect one way or the other on teen use or abuse. Of course nobody with sense wants teens to abuse anything. Every person, including teens, needs to learn how to be well rounded and not become heavy users or abusers of anything, therefore not dependent on anything. Raise your kids right like my parents did and use of alcohol or marijuana never interfered with my success in life. As a matter of fact alcohol has been detrimental to some people I know. Marijuana. Not one.

  23. This would’ve been a more interesting study if not all subject had a history of “severe dependency” (personality flaw).

  24. I personally think this is a crock of crap. I know that my sister is a brilliant person and she smokes marijuana every day. She runs circles around me when it comes to knowledge. She has been smoking over 25 years daily. I know what this study is, it is the DEA and FDA trying to get their grubby hands in the money pot that will go away if they find marijuana safe. Kind of odd this study comes out right before the DEA and FDA are suppose to try and regulate it to a lower schedule. I want to see this study.

  25. This is another correlation doesn’t equal causation type of study. In addition to the small sample size of 11, the question that isn’t answered in the study is whether or not marijuana causes a decreased dopamine response, or whether individuals with a preexisting low dopamine response gravitate towards recreational drugs as a way to self medicate.

  26. Should be more worried about the people dying as direct and indirect result of legally prescribed drugs approved by the FDA and pushed by big pharma.

  27. This study was done by a research institute which is known to be bias and anti-drug, and has also been involved in many controversies.

  28. Testing during the withdrawal phase? Idiots. The dopamine reproduction rebounds in a few weeks to months, , .

  29. “We don’t know whether decreased dopamine was a preexisting condition or the result of heavy cannabis use,” said Dr. Abi-Dargham. “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.”

    So they are guessing, again……………… “we don’t know, and “may”? What a crock. “But the bottom line is that long term, heavy cannabis use” means this guy is anti cannabis.

    And what is “heavy cannabis use”? One hit a day?, 5, 10, 20? And how potent is the cannabis they used in the research? I certain that another “study” will show that cannabis actually increases dopamine in the brain.

    Alcohol is the devil drug, kills brain cells, livers, innocent bystanders, families, unborn children, the list goes on….. What about the bottom line long term heavy alcohol use? Equals death, and death to others that don’t even consume it just for being near the ones that do.

    1. Exactly!! Once I got to that one line, ” We don’t know whether decreased dopamine was a preexisting condition or the result of heavy cannabis use,” said Dr. Abi-Dargham. “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.” I stopped reading. Hello biased morons, they said I would go blind from masturbating.. here I am almost 50 still smoking etc … I am happy and because of medical marijuana I am ALIVE!!!! Oh and I can still see perfectly fine..so enough with the BS. Hey DR how many people have DIED from cannabis??? Yeah thats what I thought .. the amphetamine YOU gave your patients, that DOERS cause MANY MANY deaths every year worldwide. So what other deathly toxins did you introduce during you test of the non-lethal cannabis? Yahoo articles are steeped in ignorance and that is why I hardly read them.

  30. First off, No one is dependent on marijuana. Once I read that in the first paragraph I disregarded the whole thing. Nice try though. It is not addictive. Just because you want to do something daily does not make it that way.

  31. this “dr.” clearly has little or no evidence if you read the research. Hey genius did it ever occur to you to prescreen the test subjects for lack of dopamine use before the study as you mentioned after the fact that you probably should have? Also this guy’s career revolves around doing whatever he can to make Canabis look like something horrific. Check his curriculum vitae. What a loser

  32. Research on Cocaine has found that the using Cocaine, long term, permanently disrupts the natural production of Dopamine. Other studies have found that after stopping heavy Marijuana use, natural production of Dopamine resumes to normal levels. What other drugs PERMANENTLY disrupt the natural production of Dopamine, and do not return to normal levels after cessation, S.S.N.I.’s. Not all substances that effect Dopamine production are the same. Alcohol, as one example, causes the release of Dopamine in the Ventral Striatum, while at the same time increasing the levels of G.A.B.A., an inhibitory neurotransmitter, which accounts for the depressant effect of alcohol.
    Given enough time and funding, one can come up with whatever result the funding stream desires. Really, how many people have read about the studies concerning the potential for needing to take S.S.R.I.’s for LIFE, just to feel normal; or how about the INITIAL studies that stated only 1% of the patients taking S.S.R.I.’s experienced withdrawal, As the companies manufacturing those drugs are now being sued, the reality the upwards of 50%, or more, of the patients experience withdrawal as they attempt to stop taking these S.S.R.I.’s.

  33. Anandamide terpene is only found in cannabis and cocoa and it creates euphoria and forgetfulness. So how come the same negative research isn’t being performed on Chocolate? Spin it doctors, you can try, but the fact remains, nobody has died ever from cannabis. It’s hippocratic and it only heals and does no harm, that is, unless you think chocolate is harmful.

    1. You are so incorrect. Anandamide is an endocannabinoid made in mammals. It is not a terpene either, terpenes are synthesized in plants…back to school for you!

    2. Although there was no difference between groups in task performance, in all participants lower dopamine release was associated with worse performance on both tasks

      This is my favorite comment…NO DIFFERENCE between groups on task performance…and it doesn’t matter if you were a heavy Cannabis user or not a user…this only says if you had low dopamine, you did poorer on the test. This is called writing up your work to fit your agenda…the agenda is still the same , deamonize a healing sacred plant so that people cannot take their healthcare into their own hand…here have some more pills instead!

      This is all you need to know to disregard this study:
      Funding: Funding for this study was provided by grant R01 DA022455-01A1 from the National Institute on Drug Abuse to Dr. Abi-Dargham.

  34. How much were these people smoking? Dependence is a strong word but its not a number. Not all the users smoked daily. What about other substances? Was there any “dependent” use of other drugs. And also, if there was no difference in the cognitive abilities of each group, are the results based on the individuals? If so,How many of each side struggled? I dont doubt that it effects the dopamine or other brain chemicals. I dont doubt its not good for developing brains. I understand the govt is still skeptical of anything positive but these studies need to be done. If they want to be taken seriously then answer all the factors.

  35. Only 11 people can this even be considered a study? Although there was no difference between groups in task performance, in all participants lower dopamine release was associated with worse performance on both tasks. I thought there was NO difference.
    “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.” So in other words you don’t know.

  36. I am really getting tired of people talking about people being “dependent” on marijuana. I am a 40 year smoker. 40 years now. Sometimes every day heavy for years. Sometimes just in the evening. If I have it I smoke it; if I don’t, no big deal. I’m on a dry spell right now, just can’t afford it. No big deal. People who are “dependent” on marijuana would be dependent on anything – alcohol, chocolate, TV, shopping, computers.

  37. If you are impulsive, love reading the Wall Street Journal, tend to go on shopping sprees and spend too much money, then you might need these effects. If you can’t read a book, have never read a book, and never plan on reading anything, never go shopping, and nothing is interesting, then THC is just going to make it worse.

  38. The gold standard of marijuana research is found in the major government commissions on marijuana – including President Nixon’s Shafer Commission of 1972. All the major commissions have concluded marijuana is not addictive, is less harmful than alcohol and should be regulated as is alcohol. The reports of all these major commissions can be read on-line at the Schaffer Drug Library.

    The DEA’s own administrative law judge, Francis Young, concluded after an exhaustive review of the evidence: “Marijuana, in its natural form, is one of the safest therapeutically active substances known to man.”

    Alcohol directly kills more than 50,000 Americans every year. It kills many thousands more in highway deaths and from alcohol-induced violence. The preponderance of the research shows marijuana consumption is neither a significant cause of auto accidents, nor violence.

    NO ONE has ever died from ingesting marijuana – in all of recorded history. – In that regard, it is safer than aspirin, coffee and peanuts!

  39. The most significant points of this article:

    >>>”there was no difference between groups in task performance.”

    Do tell.

    >>>”“We don’t know whether decreased dopamine was a preexisting condition or the result of heavy cannabis use,”

    That BIG area of ignorance. – Could be, dopamine deficient people compensate with near harmless marijuana.

    Another junk science molehill being used to fight against ending the monstrously destructive, counter-productive, freedom-strangling FRAUD of marijuana prohibition. The gold standard of marijuana research is found in the major government commissions on marijuana – including President Nixon’s Shafer Commission of 1972. All the major commissions have concluded marijuana is not addictive, is less harmful than alcohol and should be regulated as is alcohol. The reports of all these major commissions can be read here:

    http://www.druglibrary.org/SCHAFFER/Library/studies/studies.htm

    The DEA’s own administrative law judge, Francis Young, concluded after an exhaustive review of the evidence: “Marijuana, in its natural form, is one of the safest therapeutically active substances known to man.”

    Alcohol directly kills more than 50,000 Americans every year. It kills many thousands more in highway deaths and from alcohol-induced violence. The preponderance of the research shows marijuana consumption is neither a significant cause of auto accidents, nor violence.

    NO ONE has ever died from ingesting marijuana – in all of recorded history. – In that regard, it is safer than aspirin, coffee and peanuts!

  40. victor doesn’t comprehend a lot of “non creative” people use marijuana for other purposes than just creating art. 23 people isn’t much of a study to base anything on.

  41. Victor, I think you are correct in this. As with most mind altering substances, it comes down to the individuals mind, where they are naturally deficient, either from chemical imbalances or social/life hardships and what fills the gap that allows them to feel comfortable with their own life.

    With phrases like “may cause negative effects on learning and behavior” I would like to know more specifically what behaviors would be affected negatively. I would also like to know what evidence is shown linking the hypothesis. Because, for example; I smoke and have smoked every day for nearly 10 years. And I was smoking while in college, very often being high in class with no one even noticing. I graduated with a 3.92 gpa. Granted, this was a field of study heavily influenced on creativity and hands on work as opposed to research and collaboration of data.

    I have also been told I am “the most emotionally stable person I have ever met” from 2 different people, both of which have a BA in psychology.

  42. “ We don’t know whether decreased dopamine was a preexisting condition or the result of heavy cannabis use,” said Dr. Abi-Dargham. “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 don’t know….. but the bottom line is it “may”….”

    Pretty sure the results are inconclusive. The purpose of scientific studies is to formulate a null hypothesis and try to disprove it. The goal of funded research is to prove something and is not based on that same principal but instead to find a way to prove the alternative hypothesis. Which seems to be the case here, to say that there “may” be a link which is good enough for a politician to run wild with making claims that there is direct irrefutable evidence that it “does”….. This is an example of bad science funded solely for the results to be used as propaganda against the proposed legalization or reclassification of marijuana.

    A hypothesis is a testable prediction of what you think the results of a research study are likely to be. It is a statement about the relationship between two or more variables. In statistics, the only way of supporting your hypothesis is to refute the null hypothesis.

    A null hypothesis is a working hypothesis that is to be disproved by a statistical test in favor of the alternative hypothesis. Rather than trying to ‘prove’ your idea (the alternate hypothesis) right you must show that the null hypothesis is likely to be wrong – you have to ‘refute’ or ‘nullify’ the null hypothesis. You have to assume that your alternate hypothesis is wrong until you find evidence to the contrary.

  43. You studied less than two dozen adults and came to a conclusion? Junk science pushing a social agenda at its best.

    1. And no one is sure if anyone that HUGE sampling had a preexisting condition. Where did this clown get his grant!?

  44. This article does actually mention this possibility, but I think it is more likely that a pre-existing condition which results in lower dopamine levels causes addictive behaviors, rather than THC causing lower dopamine levels. Lower dopamine generally means worse impulse control, and people with naturally poor impulse control are going to be more susceptible to trying and becoming dependent on drugs.

  45. But big Pharma has a solution. Leva-dopa. When I pick up my green dopa, I then go to the pharmacy to get the leva-dopa.

  46. “We don’t know whether decreased dopamine was a preexisting condition or the result of heavy cannabis use,” Even the research team doesnt know? Then this study is not reliable. Cant call it proof if you dont have a definitive answer.

  47. I always thought heavy cannabis users displayed a fundamental lack of joy. This may be why, but we also have to take into account other factors that may be involved. Such as why does the individual use cannabis to this degree. Correlation does not necessarily equate with causation. So be cautious in drawing conclusions without more evidence.

  48. “Dr. Haney has received partial salary support for investigator-initiated studies from Insys Therapeutics Inc and Lifeloc Technologies and has served as a consultant to Aelis Farma and Health Advances LLC. Dr. Kegeles has received research support from Amgen. Dr. Slifstein has received research support from Forest Laboratories, PierreFabre, CHDI, and Otsuka and has provided consultation for Amgen. Dr. Abi-Dargham has received research support from Takeda and Forest Pharmaceuticals and has served on advisory boards for Roche, Forum, and Otsuka. ”

    All I need to see..to know this is a bunch of horsesh1t biased propaganda…

  49. Quote
    “We don’t know whether decreased dopamine was a preexisting condition or the result of heavy cannabis use,” said Dr. Abi-Dargham.
    Unquote

    So these people are just joking,hmm…… not funny.

  50. Of coarse THC effects dopamine and we will find it alters other brain chemicals. THC is not for everyone. It is negative for people who do not have the creative side of their brain. Non creative people hate THC while creative people love it. If we have a cavalier attitude about THC and make it available it will harm the brains and give negative reactions of non creative people. THC is a double edged sword. it is positive for creative people and a neurological liability for non creative people. We have to be very careful with this herb.

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