Does Marijuana Cause Brain Damage?

Repost from the old site.
Fortunately for users, many of the most worst accusations against marijuana have not yet panned out. One of the most frightening is the specter of permanent brain damage. For instance, according to this site, marijuana:

affects, alters, and damages brain cells controlling thinking, emotion, pleasure, coordination, mood and memory. The pituitary gland is also damaged, which regulates hunger, thirst, blood pressure, sexual behavior, and release of sex hormones.Marijuana accumulates in the microscopic spaces between nerve cells in the brain called “synapses.”
This clogging interferes by slowing and impairing transfer critical information. Long term use causes the brain to stop production of brain chemicals necessary to “feel good” – a negative feedback condition. And, the user becomes chemically addicted to marijuana.

These studies may be related to the famous Heath monkey studies done in the 1970’s. A recent attempt by William Slikker in Arkansas and Charles Rebert and Gordon Pryor of Stanford Research Institute to replicate Heath was not able to replicate any of his frightening findings. There was no brain damage whatsoever in Slikker’s and the SRI Group’s monkeys.
In the early 1990’s, I conducted interviews with both Rebert and Pryor about these studies. At one point in the interview, an exasperated Rebert said, “Forget it. Cannabis is not neurotoxic.” Pryor had no explanation for the discrepancy between his findings Heath’s.
There is no evidence that THC “accumulates in synaptic gaps and clogs them up.” There is also no evidence that marijuana causes the brain to “stop producing feel good chemicals.” I am not sure where they are getting that one from. Recent studies show no long-term changes in brain chemicals from marijuana use.
Neither is there any evidence that, in a broad sense, cannabis causes “…damages brain cells controlling thinking, emotion, pleasure, coordination, mood and memory.” There is a possibility that cannabis use may impair the brain’s ability to winnow out extraneous stimuli to focus on one thing, but this is not yet proven. Nor is there any evidence of damage to the pituitary gland.
This post in its original form was far too long. I have decided to break it up into seven different posts, in addition to this post. The separate sections are listed below.
For an examination of the evidence of whether or not cannabis causes actual structural damage to brain cells, axons or dendrites, see here.
For an analysis of neuropsychological batteries of cannabis users to determine whether or not they suffer brain damage, see here.
For an analysis of EEG testing of cannabis users to discover evidence of brain damage, see here.
For an analysis of studies looking at cerebral blood flow in cannabis users, see here.
For an admittedly impressionistic analysis of whether or not cannabis causes schizotypal symptoms in users, see here.
For a summary comparing the effects of cannabis on the brain compared to other drugs, see here.
For a summary of the findings of cannabis and brain damage, see here.

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23 thoughts on “Does Marijuana Cause Brain Damage?”

  1. they say eraly marajuana use alters gene expression permamnently, is this true? at what age is the risk? and how much can cause it?

  2. robert,
    i found out that it dosent necesaraly change gene expression and its more of a risk for young adolescents with heavy use for a long time, our body has a fantastic way or repairing itself, even certain foods can do this infact our genes are under bombardment everyday from allsorts of environmental stressors and our body is in constant repair, so thats sorted.

  3. Your links arn’t working anymore. Why have you taken the articles down? I was looking forward to a good read.
    I don’t know. I’ve been browsing through medical journals myself and have found studies that have pointed towards evidence of impaired cognitive ability in chronic daily users, especially those during adolescence.
    By the way that you’ve written your articles it seems to me like you’ve written them with the intention of proving a cause; The word “bias” comes to mind; Instead of researching both “sides of the argument” and then deciding which seems more realistic to you after appropriate open-minded thought.
    I could be wrong. I’ll never know til you get those damn links working.

  4. Okay kids, let’s go back to the uninformed stone-age where we all believe b.s. and propaganda. Of course it doesn’t cause brain damage. It may cause temporary chemical imbalances or amplify them in certain people, but it most certainly does not cause damage.
    It’s actually been proven to do the opposite. THC coats your brain cells and protects them from damage caused by injuries, disease, and alcohol (and other drug) abuse.
    People, get your facts straight and open your minds. We don’t live in the seventies anymore. It’s 2011, and we now have advanced technology to dismiss idiotic, biased claims such as this.

    1. Fuck yes, this guy knows whats up, the person at the beginning said “of course it בause נrain גamage what kind of question is that?” he is theone with brain damage

  5. I have been smoking NYC dirt weed for 15 years. I found your site doing a search trying to find out how to repair the damage I feel it has done to MY brain. I can’t remember anything, I’m unfocused and have no drive. Big dreams, genius ideas, none of the drive it takes to execute them. All of my female pot head friends are the same way. Maybe THC works differently in conjunction with estrogen or something?
    I don’t care whether or not anybody else smokes weed or if it gets legalized and I don’t have any “agenda”. I’m just looking for a way out of the fog.

    1. Pay no mind to Robert Lindsay. He is only a cog in the machine of propaganda. The same exact problems occurred to me as you’re explaining, DalaiMamaRBG, and I found out the issues were a result of vitamin & nutrient deficiency, dehydration, and a lack of exercise.
      Once I started taking supplements, drinking plenty of water, and exercising about 20 minutes a day (jogging, sit-ups, push-ups), I started coming back to my senses. I am now back to the point I used to be (after only ONE MONTH!), and am extremely happy with my life. I no longer feel any dependence on any drug (besides that damn nicotine!), and I’m back to being quick, witty, cognitive, and able to hold conversations much, much better. I am out of the proverbial “fog” that some of us are unlucky enough to experience.
      Now, any time I smoke, I don’t get paranoid or self-conscious anymore, and I can finally relax, have really deep, intellectual conversation, and just enjoy myself and my surroundings.
      Here, I’ve listed for you the vitamins and supplements I used to turn my life back around and to feel positive emotions again:
      Vitamin B6*
      Vitamin B12*
      Niacin–Vitamin B5*
      Vitamin C
      Vitamin D
      Omega-3 Fatty Acids (Fish Oil)
      * = Included in B-complex, but not in optimal amounts. (Opinion)
      NOTE: You can find certain tablets such as One-A-Day that will contain all of these and more vitamins and nutrients, but in my opinion, do not always provide optimal amounts. That’s why I buy them all separate and add a One-A-Day to my regime. Since I’m feeling healthy and happy again, whenever I run out of these supplements, I think I will THEN insist on taking just a One-A-Day and Fish Oil.
      Two other supplements that have helped with depression and memory would be Ginkgo Biloba and St. John’s Wort. Some people will have adverse effects such as being irritable or negative changes in mood. For most, however, these will further help promote happiness and enhanced cognitive thinking.
      ***Don’t start taking these until you’ve already been on your vitamin regime for about a week or two.***
      I would also like to mention I stayed sober throughout my whole recovery process, and I can’t say whether or not it helped, but I would infer that it would probably help, and I STRONGLY encourage you to try to stay as sober as you possibly can during this stage. No weed, no alcohol, no caffeine, no cigarettes (I cheated on that one. :P), and no other drugs, at least temporarily, so you can give your mind a break from all the brain activity going on.
      Tell me how things go for you, DalaiMama! Just remember you can and will get through this confusing bullshit!
      Oh, and for Robert: Instead of just saying, “Quit smoking pot,” why don’t you actually attempt to see the huge amount of other plausible reasons? I’m not saying marijuana is a wonder drug and everyone should be using it or anything; I’m just pointing out the facts that you so easily dismiss in your logic.
      YES, marijuana amplifies your emotions, and if you’re already feeling depressed, self-conscious, paranoid etc. BEFORE you smoke, these negative feelings will almost always just be amplified after you smoke.
      The same goes for a lot of drugs, and before you dabble into any drug-use, you need to make sure you are healthy and already in a positive state of mind prior to the experience. Excessive use (abuse) of marijuana CAN cause vitamin deficiencies, which can potentially trigger chemical imbalances in your brain, which lead to these negative feelings and the “fog” some people experience. This is why it’s very important to make sure your health is in check, and you’re getting enough vitamins, minerals, and other supplements.

      1. I am very happy to hear that you are still able to get high without experiencing the down side of cannabis. My cannabis using days may not even be over yet, but I haven’t smoked it in 2 1/2 years. I used it for over 20 years. One of my favorite drugs, but then I like a lot of drugs.I’m a drug fan.

        1. Robert,
          I apologize for my ignorance. I read through your article the first time and misconstrued your message. It appeared to me that you were against marijuana and were actually supporting the claims proposed by those biased doctors and scientists.
          I read through a second time and saw that you were actually dismissing those ridiculous claims. *facepalm* I feel like such a jackass now…
          Anyways, great article and I hope you can someday smoke again without any negative emotions! I suggest the advice given above to absolutely ANYONE experiencing depression, anxiety, poor memory/concentration, lack of self-confidence, lack of emotion, negative feelings while under the influence of drugs, or really, just any mental or emotional problems.
          SO many people ignore these 3 essentials: nutrients (diet), water, and exercise, and instead, they look for medicinal alternatives like SSRI’s or other prescription drugs. Most of the time, these drugs only amplify the problem instead of fixing it, and it’s just a ploy used by pharmaceutical companies to keep the money flowing towards them.
          PLEASE, for the sake of your mental, physical, and emotional health, try these three safe, cheap, all-natural cures for your problems BEFORE taking any pharmaceutical drugs for them.
          Once again, thanks for the good read, Robert. I sincerely apologize for criticizing you so harshly, but please–do look around to find alternative reasons to mental/emotional troubles rather than rushing to the conclusion that drugs are the cause. I still promote sobriety when going through healing stages, however.

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