The rest of the story: "Cannabis harms brain, imaging shows"

For those who are trumpeting marijuana as God's gift to PwPs, and one moreover that is maliciously suppressed by the powers that be, here is recent news to help them curb their "irrational exuberance." OK folks, I have no dog in this race, and am personally not concerned one way or the other, but I am bothered that a sequence of posts I saw here on the role of medical marijuana were all pro, with no con. Biomedical issues are seldom, if ever, one-sided. The above, recent research may help restore a more sane, nuanced, and balanced view. Let's proceed, and take chances, but without clinging too tightly to our beloved hobbyhorses.

12 Replies

  • I do not want to join Medscape to view this article. i'll take your word.

  • Sorry, Royprop, I did not realize that membership signup on Medscape (free) would be an impediment. So, for convenience, let me paste here the beginning and the end of the article :

    BALTIMORE — The heavy, long-term use of cannabis is associated with negative changes in parts of the brain not previously implicated, and is linked to deficits in learning and memory, new research suggests.

    "In light of a current trend toward legalizing marijuana, with potentially increased exposure of adolescents, we believe our findings are important to consider," said investigator Jodi Weinstein, MD, from the Columbia University Medical Center and the New York State Psychiatric Institute in New York City.

    If used daily, cannabis "can be as bad as other drugs in terms of consequences," said senior investigator Anissa Abi-Dargham, MD, also from the Columbia University Medical Center and the New York State Psychiatric Institute.

    "People often think of cannabis as a lighter, harmless drug. This study shows that it is not and that it has negative consequences," she told Medscape Medical News.

    The study results were presented here at the Society of Nuclear Medicine and Molecular Imaging 2015 Annual Meeting.

    The team used the highly specific carbon 11-labeled (+)-4-propyl-9-hydroxynaphthoxazine radiotracer — known as [11C]PHNO — to image the impact of cannabis on the brain. The radiotracer binds preferentially to dopamine D₃ receptors. Because it is a different class of compound than most other D₂ and D₃ radiotracers — an agonist rather than an antagonist — it is sensitive to dopamine release.

    People often think of cannabis as a lighter, harmless drug. This study shows that it is not and that it has negative consequences.

    With [11C]PHNO, the investigators showed that heavy chronic cannabis use is associated with lower dopamine release in the associative striatum and the sensory motor striatum, regions involved in cognition.

    . . . . . . . (skipping to last page of article) . . . . . . .

    "Our study provides definitive evidence that in heavy cannabis users, there is a detectable deficit of striatal dopamine release using an amphetamine challenge," said Dr Weinstein. "Within the striatum, the subdivisions seem to have a different pattern, in contrast to reports of other substance abuse. And our exploratory analysis suggests that the deficits we are seeing in dopamine release in the striatum have a functional significance — that lower dopamine release is associated with lower working memory and learning performance."

    This could be linked to the addictive potential of cannabis and other problems, such as lack of motivation, seen in regular users.

    For schizophrenia, this study suggests "a potential mechanism by which cannabis may be contributing to the risk for psychosis or the severity of psychosis, specifically by interfering with dopamine transmission in one key brain region involved in psychosis — the head of the caudate," added Dr Abi-Dargham. "If this is repeatedly occurring at a young age, it could result in abnormal salience and could have offsite effects on the circuitry. These comments obviously are a little speculative, but can be further tested now that we have this information," she pointed out.

    "This study is striking in that it provides further evidence that long-term cannabis use is associated with alteration in the function of key brain chemical messengers — in this case dopamine, a key chemical messenger for motivation and attention," said Oliver Howes, MD, from the Institute of Psychiatry at King's College London, United Kingdom.

    "The blunting of dopamine release that they find fits with other studies showing reduced dopamine synthesis in cannabis users. This could be linked to the addictive potential of cannabis and other problems, such as lack of motivation, seen in regular users," Dr Howes told Medscape Medical News.

    Although "previous studies, including a study from the same group, did not show significant differences in striatal dopamine function between chronic cannabis users and controls, those studies used a more traditional tracer, raclopride, which binds to both dopamine D₂ and D₃ receptors," said Matthijs Bossong, PhD, from the Brain Center Rudolf Magnus at University Medical Center Utrecht, the Netherlands.

    This study "used a specific dopamine D₃ receptor tracer, which suggests that striatal dopamine D₃ receptors are particularly involved in cannabis dependence," he explained. It also suggests that "[11C]PHNO may actually be a better tracer to measure acute dopamine fluctuations in the striatum. It has a better sensitivity."

    **** End of Medscape article ****

    To weigh the foregoing negative research results on Cannabis against many positive ones, you may go to the following site, and enter "Parkinson's" into their search box:

    The above site,, is dedicated to legalizing marijuana use. So it is possible that the links they offer are skewed toward positive reports on the medical benefits of cannabis. I don't know. You be the judge.

  • Thanks for the info. It is good to see both sites of the coin.

    While talking about cannabis there is always a tendency to talk just about THC and base those studies just on this particular compound.

    There are a lot more cannabinoids on cannabis (CBD, CBG, CBC, CBDA, CBDGA....)

    We should have a close look to the CBD which it is non-psychoactive, counteracts THC and it seems it has a lot of medical power.

    What's CBD Good For?

    Science suggests that medical marijuana—CBD, in particular—may be helpful for many conditions. But don’t take our word for it. Our friends over at Project CBD have pulled together much of the research on cannabis' use as a therapeutic. Choose a condition to see the science. Visit Project CBD for additional information.

    Nice short video and pie chart to be printed at the end of this article.

    If you did not see it at its time just meet Charlotte Figi.

    WEED - A CNN Special Report by Dr. Sanjay Gupta (Full HD 1080p - 2013 Documentary)

    it is important to keep searching and listen to both parts.

    Kind regards

  • Hi Eduga, Thank you for providing all this material. Great food for thought. I have so far watched WEED, parts 1 and 2 with Dr. Sanjay Gupta. These videos makes it clear that vast researches need to be pursued on the medicinal benefits of marijuana. As the research starts to produce high-quality meds, a struggle will be going on to overcome the barriers (social, political, legal, economic, technical) limiting access and supply. Israel and Europe, seem to be far ahead of the US in these developments. The latter needs to catch up.

  • Hey a year late and a dollar short. I am really interested in your view. My state is having a vote on whether to legalize it or not, it is legal for medical purposes. I am really conflicted about the outcome. If you legalize it will it stop the medical testing on it. Why try to prove something is beneficial if its already legal. Its a no brainer, that pot can be used for pain, relaxation, and for sleep just like alcohol. The big difference is alcohol kills brain cells and CBDs seem to be neuroprotective. Walk into a dispensary and there seems to be a wall full of products. Herbs in glass jars showing the beautiful flowers and the wonderful bouquet and 19% htc level. There are edibles, vaporizers, gummy chews all with the (get stoned) sales pitch. There on a shelf about a foot wide are all the products that have been geared to the medical side. Vape pens that give out doses in coconut oil, tested with a HPLC and liberated from the plant with carbon dioxide not butane. You can actually give a Doctor test results showing just how much of each chemical is in the oil and amount for each puff. They can then look at your current meds and see if there is any potential problems. I am concerned that once legalized why spend extra money testing it. It will become like wine, I couldn't pick out the difference between an 8 dollar or a 40 dollar wine.

  • Sirshakes, I wlll have to give this a pass since I am not sufficiently versed in this vastly complex issue:

    Personally, for myself, I do not approve of recreational uses of psychoactive substances--the strongest thing I use is caffeinated coffee--and in the last few years, it has, regrettably, lost the ability to keep me awake. Medical marijuana, once it has been well-researched and proven safe, is another story.

    My wife, who is more worldly-wise than me, agrees with you that legalizing recreational weed would tend to suppress research on medical marijuana. Big Pharma will still research and market extracts of the plant, but who knows what sky-high prices they may charge.

  • Thank you for your reply. I don't have a problem with the medical side. My brain is already shorting out. I went 51 years without pot and a just say no attitude so I am LPnew to this. I see that some profesionals are really sincere in their belief that this is a cure all. I believe that it can be another bullet in an arsenal to get you through the hard times. I am also looking at testosterone pellet therapy. It does help. I know why Doctors don't like it. It's to abstract. I know that running analytics are very expensive and believe that if legalized why test it. Only people like me will care. Again thank you. I know you don't want to be attacked but I am very analytical and want to know what is going inside of me. Again thanks for your reply.

  • What is "LPnew"?

  • its a combination of using a smart phone,no glasses, and fat parky fingers. lol

  • Sirshakes,

    So, just to make sure I understand your concern, let me try and run it by you. In the future, recreational marijuana will be legalized in all 50 states. Then the drug companies will stop (or not start) doing research into the medical applications because most folks will just buy the cheap, generic weed available in the corner store. As a result, the customer base for costly prescription weed will have evaporated. OK, is that your nightmare scenario?

    I think it is not going to be so simple. There will always be a market for high-end, prescription weed for people with acute, or very specific medical needs. The customer base will remain sizable enough because health insurance will make it affordable to the middle class. And besides, there will still be a big customer base in other countries (UK, Israel, etc.). True, we're tending towards a globe uniformly covered with strip malls, Walmarts, and McDonaldses. But we haven't gotten there yet. There's still some diversity, with enough affluent consumers to prop up medical research worldwide.

  • I guess I see whats going on with pot something like wine. Yes after years they the will come to a conclusion that a glass or two a day actually might be beneficial. All In moderation. I just can't see Dr. writing a prescription for AC/DC, high in CBDs and low in THC. Stay away from the Girl Scout Cookies to much THC, and take no more than 2 blunts a day.

  • Thank you for this posting.

    I would be interested in finding out what kind of cannabis was used. 50-50 CBD and THC? 100 percent CBD, or mainly THC? How was it ingested? And what strength? These things can make a big difference.

    Let's hear it for further research!

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