Study finds abnormally low blood flow in the brain of marijuana users

Hippocampus, the brain's key memory and learning center, has the lowest blood flow in marijuana users suggesting higher vulnerability to Alzheimer's. As the U.S. races to legalize marijuana for medicinal and recreational use, a new, large scale brain imaging study gives reason for caution.

Published in the Journal of Alzheimer's Disease, researchers using single photon emission computed tomography (SPECT), a sophisticated imaging study that evaluates blood flow and activity patterns, demonstrated abnormally low blood flow in virtually every area of the brain studies in nearly 1,000 marijuana compared to healthy controls, including areas known to be affected by Alzheimer's pathology such as the hippocampus.

All data were obtained for analysis from a large multisite database, involving 26,268 patients who came for evaluation of complex, treatment resistant issues to one of nine outpatient neuropsychiatric clinics across the United States (Newport Beach, Costa Mesa, Fairfield, and Brisbane, CA, Tacoma and Bellevue, WA, Reston, VA, Atlanta, GA and New York, NY) between 1995-2015. Of these, 982 current or former marijuana users had brain SPECT at rest and during a mental concentration task compared to almost 100 healhty controls.

Predictive analytics with discriminant analysis was done to determine if brain SPECT regions can distinguish marijuana user brains from controls brain. Low blood flow in the hippocampus in marijuana users reliably distinguished marijuana users from controls.

The right hippocampus during a concentration task was the single most predictive region in distinguishing marijuana users from their normal counterparts. Marijuana use is thought to interfere with memory formation by inhibiting activity in this part of the brain.

According to one of the co-authors on the study Elisabeth Jorandby, M.D., "As a physician who routinely sees marijuana users,  what struck me was not only the global reduction in blood flow in the marijuana users brains, but that the hippocampus was the most affected region due to its role in memory and Alzheimer's disease.

Our research has proven that marijuana users have lower cerebral blood flow than non-users. Second, the most predictive region separating these two groups is low blood flow in the hippocampus on concentration brain SPECT imaging.

This work suggests that marijuana use has damaging influences in the brain - particularly regions important in memory and learning and known to be affected by Alzheimer's."

Dr. George Perry, Editor in Chief of the Journal of Alzheimer's Disease said, "Open use of marijuana, through legalization, will reveal the wide range of marijuana's benefits and threats to human health.  This study indicates troubling effects on the hippocampus that may be the harbingers of brain damage."

According to Daniel Amen, M.D., Founder of Amen Clinics, "Our research demonstrates that marijuana can have significant negative effects on brain function. The media has given the general impression that marijuana is a safe recreational drug, this research directly challenges that notion.  In another new study just released, researchers showed that marijuana use tripled the risk of psychosis. Caution is clearly in order."


  1. Mitchell Burk Mitchell Burk United States says:

    My mother died of Alzheimer. She never smoked anything or drank alcohol what so ever.
    To tell the truth nobody knows what the effects are . The native American Indians have been smoking pot before we even know what is was . It is the only 100% natural herb that can be smoked as is without mans interference. So in reality you don't know any facts. In light that shut up about things you know nothing about .

  2. Rowen Mayfair Rowen Mayfair United States says:

    Does it lower blood pressure?

  3. Woody Nelson Woody Nelson United States says:

    Have you seen the study of what a brain looks like after alcohol consumption and worse yet the brain of an alcoholic? I have.

  4. Charles S Charles S United States says:

    Could you please explain how this is similar or different to the effects of caffeine?

    • James Moore James Moore United States says:

      To equate reduced blood flow with Brain damage is insane, IMO! The fact that most folks who drink coffee daily are reducing their brain blood flow, as Charles S. points out ( ), means that most of the US population is Brain damaged from drinking coffee... NOT... so if they are drinking coffee and smoking pot daily... they should be brain dead for sure... NOT... Just stupid logic. Eastern meditating Yogis and other who have practiced the art of being able to down regulate their blood flow and other metabolic functions, can survive for extended time on very little oxygen, and no food or drink either. It is documented that some of these amazing meditative states are almost clinically dead, according to vital signs. None of them have ever been damaged mentally from such reduced blood flow, so reduced blood flow doesn't always equate to tissue damage! Don't read into, or assume negative conclusions based upon reduce blood flow to the brain... it probably happens every night and is essential to health and maintenance of the human body, and mind. That is true! End of story.

  5. Johnnie Dorman Johnnie Dorman United States says:

    It's been known for years that cannabis lowers blood pressure, which helps those with high blood pressure, so this article is just another bogus piece of propaganda put out by those who will lose profits because of the legalization of cannabis. Alcohol causes more brain damage than cannabis ever did, yet we don't see anything like this article about alcohol being a health concern. That's how lie filled propaganda works.

  6. Alouisis anon Alouisis anon United States says:

    The study examined test data from patients being evaluated for complex, treatment resistant issues. There is no control nor any examination of healthy patients. Therefore, the conclusions do not demonstrate anything of value other than a compilation of data that may be compared to a control group in some future study. This study has inadequate data to draw any conclusions.

    in other words, More Reefer Madness.

  7. Tim R Tim R United States says:

    Hippocampus, the brain's key memory and learning center, has the lowest blood flow in marijuana users suggesting higher vulnerability to Alzheimer's. As the U.S. races to legalize marijuana for medicinal and recreational use, a new, large scale brain imaging study gives reason for caution.

    Or it could give us hope that it is a cure for Alzheimer's.

    • Storm Crow Storm Crow United States says:

      The THC in cannabis PREVENTS the deposit of amyloid plaque in the brain. “THC blocks an enzyme called acetylcholinesterase, which speeds the formation of amyloid plaque in the brains of people with Alzheimer's disease. The Alzheimer's drugs Aricept and Cognex work by blocking acetylcholinesterase. When tested at double the concentration of THC, Aricept blocked plaque formation only 22% as well as THC, and Cognex blocked plaque formation only 7% as well as THC.” From “Marijuana May Slow Alzheimer's” at WebMD.

      And furthermore, THC activates the CB2 receptors which can do this- “The activation of cannabinoid CB2 receptors stimulates in situ and in vitro beta-amyloid removal by human macrophages” and  “Activation of the CB(2) receptor system reverses amyloid-induced memory deficiency”    (both at PubMed).

      (FYI- THC activates the anti-inflammatory CB2 receptors;  in situ means on the site, in this case in a brain; in vitro means in a test tube;  macrophages are your “clean up crew” cells.)

      And one last quote- "individuals who smoked marijuana in the ‘60s and ‘70s, who are now entering their 60s and 70s, are not getting Alzheimer’s at the rate they should be." – Dr. Gary Wenk, PhD, professor of neuroscience, immunology and medical genetics at Ohio State University.

  8. Mr. Rock Mr. Rock United States says:

    Numerous other studies have shown cannabis is beneficial in combating Alzheimer and that it is active in prohibiting the growth of toxic amyloid plagues on the brain that are part of the disease.  This article, like most that are anxious to portray cannabis as bad, leaves out a lot of facts. How much was blood flow reduced?  Was it enough to cause damage?  Did any of the subjects exhibit symptoms that could be contributed to reduced blood flow?  How much cannabis did the subjects smoke and for how long?  The answer is they don't know because its a statistical study using tests that were NOT made for the purpose of studying cannabis. Notice there is no mention of who sponsored the study. This is not science, its propaganda.

  9. Ann Ruddy Ann Ruddy United States says:

    Alcohol, benzoids, opiates, nicotine,  contact sports all contribute to brain damage. I'm an amateur  genealogist and I can testify that lots of people born in the last two centuries suffered senility and mj was not a significant, if any factor in their lives. Now that's not a scientific disclaimer, but it does tell me something: "Chill!"

  10. Charles S Charles S United States says:

    Could you explain how these effects are similar or different to the reduced cerebral blood flow effects found with coffee/caffeine use?

  11. turdgobbler balls turdgobbler balls United States says:

    Just another worthless article ...what about all the studies showing the efficacy marijuana in Alzheimer patients

  12. Jennifer Wickline Jennifer Wickline United States says:

    How many people with Alzheimer's used marijuana? How often? if at all.

  13. Herman Allmaras Herman Allmaras United States says:

    Bummer about this study, better continue to lock users of cannabis in cages then.

  14. Daniel Stockwell Daniel Stockwell United States says:

    It has been shown that smoking marijuana acts as a bronchial dilator which increases oxygen levels in the blood. We also know that marijuana is a strong anti inflammatory.  One theory is we live in an inflamed state and need cannabinoids to bring that under control for full health. Inflammation increases blood flow into an area. Better oxygenated blood needs less blood so blood flow comes down lessening inflammation to the brain this is one of the protective aspects of cannabis for the brain. It is OK.

    • Storm Crow Storm Crow United States says:

      Omega 3 is anti-inflammatory! Omega 6 is pro-inflammatory. You can not properly make CB1 receptors without omega 3. Most people have a damaged endocannabinoid system due to a dietary imbalance of Omega 6 to Omega 3.

      Earliest study on this is "Nutritional omega-3 deficiency abolishes endocannabinoid-mediated neuronal functions" (PubMed - 2011). Here’s the key sentence- “In n-3-deficient mice, presynaptic cannabinoid CB(1) receptors (CB(1)Rs) normally responding to endocannabinoids were uncoupled from their effector G(i/o) proteins.”

      Basically, defective CB1s can't heal you or get you high! When you supplement with Omega 3, your body begins to replace the defective receptors and you can heal (or get higher) with your cannabis! Takes about a month to replace enough "dud" receptors to get an effect!  

      Avoid using the high Omega 6 oils- corn, soy, sunflower and "mixed vegetable" oils! Use canola or hemp seed oil for Omega 3. Coconut and olive oil don't have much omega 6, but have other health benefits.

      Daniel, sorry this is so long, but this is important news. See "Granny Storm Crow's List" for more on Omega 3 and cannabis.

  15. Victor Crocco Victor Crocco United States says:

    I am 67 and I am still working full time at a stress job. I feel like I am 40 and look 20 years younger than 67. I have not been to a MD or pharmacy since I started using weed medically.  I have no body fat. MJ is a systemic anti inflammatory and keeps your body in a basic ph with no inflammation.  All you people that know people that have mental deterioration are not listening to the facts. It is fact that MJ goes to the brain and dissolves the " plaque" that causes Altiziemers and destroys the microbes that bring the " plaque" to your brain. you have to eat the right diet for this to work for you.

    • Storm Crow Storm Crow United States says:

      Be sure to take your Omega 3! You need Omega 3 to properly make the CB1 receptors that cannabis activates to heal you and also to get you "high"! Diet is far more important than most people think! (See "Nutritional omega-3 deficiency abolishes endocannabinoid-mediated neuronal functions" (PubMed).  

      And I'm 69, and look like I'm in my 50s! My back aches a bit now and then, but overall, I feel half my age. I've retired from a life-long career in education (7th grade and Special Ed, mostly) and I retired only because of my disabled husband's failing health.  (My co-workers were shocked when I retired at 66- most thought I was much younger!)

    • porpoise boy porpoise boy United States says:

      there are SUGGESTIONS that what you say may be true for some.  regardless, ALL CANNABIS PRODUCTS should be legal for ALL legal adults, simply because it is MY BUSINESS and no one else's.  going beyond that means you are asking me to "justify" something that is NONE OF YOUR BUSINESS.  anything more and you are sticking your nose where it deserves to be smacked off your face.

  16. Darnell Wilson Darnell Wilson United States says:

    Is the low blood flow similar to calm relaxed people?
    think about that for a second

  17. Mark Todd Mark Todd United States says:

    i would like to see a list of the damage drinking alcohol does to the body. about a 1,000 times worse than anything mj does. for that matter we can talk about how beef ruins the cardiovascular system and leads to actual premature death in literally hundreds of thousands of people a year, lets outlaw beef.

  18. Cullo Veron Cullo Veron United States says:

    But keep swallowing our opiates and destroy your liver and kidneys.  Muwhahah.

    • Storm Crow Storm Crow United States says:

      Cullo, this is interesting- In “Substituting cannabis for prescription drugs, alcohol and other substances among medical cannabis patients: The impact of contextual factors” (PubMed – 2015), it was noted that “Substituting cannabis for one or more of alcohol, illicit drugs or prescription drugs was reported by 87% (n = 410) of respondents, with 80.3% reporting substitution for prescription drugs, 51.7% for alcohol, and 32.6% for illicit substances.”

      So 8 out of 10 patients found they could replace their pharmaceutical drugs with cannabis that you can grow for pennies per dose! And how well did cannabis replace those pills?

      “The three main reasons cited for cannabis-related substitution are “less withdrawal” (67.7%), “fewer side-effects” (60.4%), and “better symptom management” suggesting that many patients may have already identified cannabis as an effective and potentially safer adjunct or alternative to their prescription drug regimen.” From “Cannabis as a substitute for alcohol and other drugs: A dispensary-based survey of substitution effect in Canadian medical cannabis patients” (Informa - 2013).

      Big Pharma is TERRIFIED of legalized cannabis, and with good reason! (At age 69, the only pharmaceutical I use is thyroid pills- cannabis takes care of all the rest!)

  19. Eric Scott Eric Scott United States says:

    I don't see where the study proves whether its causation or correlation

  20. Jillian Galloway Jillian Galloway United States says:

    That's why there are no old Rastafarians around. Oh no wait yes there are. How could that be??

    Even if this finding were true, marijuana is still far safer than alcohol and people should NOT be forced to choose the more harmful substance just because the federal government has a hang up about the less harmful substance! Warnings like this could be printed on the outside of marijuana packets IF it were legal. But they can't today solely due to the ineffective and counterproductive prohibition.

  21. Adam Cusick Adam Cusick United States says:

    This article is useless. How about some actual information on the study.  How was the study conducted? How many people were studied? What was the threshold for amount of marijuana smoked in the test group? How significant was the reduction in blood flow? Answering these questions will help distinguish science from propoganda.

  22. Matt Cartier Matt Cartier United States says:

    So a bogus website that is posting a poorly written op-ed piece (That I can only assume they were paid to promote) from a notorious quack-job website that sells cures via it's supplements as well as treatments via the "brain-soul connection" (Amen Clinics) is trying to tell me that they did a test via SPECT scans (which alone are more harmful than using cannabis) and found out that it lowers blood flow? Yet they provide no data, nor do they provide any statistics.

    Ok... this is not the 1980's. People have the ability to research things on their own these days. So please cut the "Reefer Madness" and find a better way to sell your snake oil pills in a way that doesn't cause any harm to actual medicine that nature provides in cannabis.

  23. Skiz Gizzard Skiz Gizzard United States says:

    Cannabis is also linked to studies indicating it's protective anti-inflammatory relationship to the CNS. Linking this to Alzheimer's is very irresponsible.  Sorry cats out of the bag, there is no way to give the most benevolent plant that humanity has ever known a black eye.     Corporations playing corporate games in order to control the market.

  24. Shari Early Shari Early United States says:

    Big pharma are popping out supposedly legitimate studies all over to prevent the loss of all their billions of dollars if all it takes is marijuana to make someone better. They would lose billions of dollars and have to shut down if they couldn't produce medicines that "cure" a disease while killing people with their side effects. It's still more dangerous taking a lot of legal drugs than what it would be to use medical marijuana.

  25. Cody Wilde Cody Wilde United States says:

    They are just trying so hard to find a way stop marijuana legalization!!!!!!!!

  26. Parker Dane Parker Dane United States says:

    Yes, yes, yes...anything done in excess...water for instances...not enough can kill much can kill you...and it's legal.

  27. Dan Middaugh Dan Middaugh United States says:

    Perhaps but other research indicates marijuana inhibits formation of amyloid plaques, which are associated with the progression of Alzheimer's.  Give one, take one away.

  28. Roy Hopke Roy Hopke United States says:


  29. Cedric Wiley Cedric Wiley United States says:

    Another sad attempt to smear the benefits of marijuana.

  30. Sky Kuhlman Sky Kuhlman United States says:

    This article is flawed because it doesn't specify which method of ingestion was studied. Raw, decarboxylated cannabis is much different (healthier) than smoked or vaporized cannabis.

  31. Ben James Yokel Ben James Yokel United States says:

    Just more reefer madness nonsense!

    Cannabis causes soft bones, Cannabis causes gums to melt, Cannabis causes people to become booze hounds!  Cannabis causes high blood sugar. Cannabis causes low blood sugar!   Cannabis causes brain to swell.  Cannabis causes brain to shrink.   Cannabis growers cause drought!   Cannabis causes ingrown toenails!  Cannabis causes dogs and cats to sleep together (it's TRUE, I've seen it!)  

    Cannabis is still much safer than alcohol, tobacco and pharmaceutical drugs which according to data from the Center for Disease Control's kill over 650,000 US citizens annually, plus another 21,000 traffic fatalities directly attributed to alcohol and pharmaceutical drug intoxication.

    Legalize, regulate and TAX!

    • porpoise boy porpoise boy United States says:

      we should give LEGAL WEED to every homeless person drunk in the country.  within a decade our costs for dealing with the indigent would DISAPPEAR.  if EVERY ALCOHOLIC switched to weed, the avg lifespan would increase by years and 90% of liver disease would disappear. and on and on and on.

  32. Scott Cayouette Scott Cayouette United States says:

    Was there any attempt to distinguish strict marijuana users from those that also smoke tobacco and use alcohol?  Those variables need to be addressed before any conclusions can be accurately drawn as these "researchers" seem to have done.

  33. Moon Dog Moon Dog United States says:

    It must be "low blood flow" that makes my eyes red

  34. David Horton David Horton United States says:

    Compare the negative effects of pot to those of alcohol,tobacco,pharmaceuticals and caffeine to be fair about. Weed's harmless compared to those.

  35. Anthony O Anthony O United States says:

    WAKE UP!!!   I've been smoking for over 15 years and will probably never stop, but as much as I love smoking, I have to admit that I'm not as sharp as I once was. It is a FACT that smoking DOES effect your short-term memory, which in turn effects long-term memory. Most of you that commented that this article is BS, are either too stupid to comprehend reality or are too burnt out to realize that you are already experiencing the negative effects. You morons are the exact reason why weed hasn't been legalized sooner. You give all potheads a bad name. We are not all brain dead (yet). I am FOR legalizing weed too, but by refusing to acknowledge its negative effects only proves your ignorance. Weed will still be legalized, your argument will be moot, and you'll still be an idiot!

  36. Walter Ali Walter Ali United States says:

    More lies from big pharmacy

  37. Pac man Pac man United States says:

    Oh the lengths an addict will go to defend their drug of choice , until it's too late. Please, majority of people who started smoking in their teens or early 20s and continued for a decade or more are losers, MAJORITY not everyone. But that's something to consider, and yes i speak from experience. My productivity and motivation went up about 500% just 3 days after quitting pot. Also , memory recall and vocabulary improved immediately. Yes, while there's a niche with cancer patients or people who need to enhance their appetite for medicinal use, even then it's CBD that's the active ingridient not the THC that gets you mentally high.

  38. David Walker David Walker United States says:

    This is a very slanted article.  An alternative headline describing the same  finding could have been:  "The brains of marijuana users  have lower energy requirements" and the discussion could then have focussed on the reason for the efficiencies in marijuana user's brains.

  39. Christine Poe Christine Poe United States says:

    I need a few questions answered. I am a sufferer of what is called a psodu tumer. if you dont have any idea of what that is it is where my spine makes too much fluid and it gets stuck in my crainum and compresses my brain, it causes vision problems, nerve damage, and could possible shut down body organs. if this could prevent that from happening why is it bad? My brain has an accessive amount of fluid wouldn't this put it back to a normal reading? What if this is a legit way to help me and others with this problem without having to turn to surgugary? and if you say take meds i do and they dont help as much as we thought that they would ive been on them for ten years now and still no hope. please get me answers asap

  40. Paula wells Paula wells United States says:

    I think Marijuana should  be banded. it causes so many problems it  damages the brain in people. Its not a drug that can help people. It only damages the brain.

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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