27 thoughts on “New Studies Show Long-Term Effects of Cannabis on the Brain

  • April 29, 2014 at 9:12 am

    Good points and it is good to be knowledgeable. But many things approved by our society (alcohol,food, cigarettes, some activities) have side effects. It’s all a balance. Benefit vs harm.

    Also, these changes have been observed but what do they mean? Does the brain function less well with less gray matter?

    • July 3, 2014 at 1:04 pm

      Hey Gary. You’re absolutely right: everything we do, from breathing to eating to exercise to watching TV “changes the brain”. That’s the thing about the brain: it’s always changing according to what we do, think, and experience. Some of these things create “good” changes and others create “bad” changes. In this article (and in these comments), I hope that I’m being fair to marijuana when I say that some of these changes really are “bad” and some of them we don’t really know about yet. Especially for the developing brain — up to about age 25 — it’s pretty clear that marijuana does bad things. For the adult brain, it’s a little less stark…but it doesn’t look so good.

  • April 30, 2014 at 11:10 am

    Hello: have there been studies done about low THC cannabis used for medicinal purposes? If so, what do they show for both the growing brain of a younger person as well as for older people? Any pointers to sources of information as well as your own analysis of that info would also be greatly appreciated. Thanks!

  • April 30, 2014 at 11:11 am

    Ug, forgot to click the “notify me via email of responses” box, so am posting agin so I’ll be notified…

  • April 30, 2014 at 11:12 am

    I’m curious about how the researchers in the second study defined ‘heavy use’ and also whether the decrease in grey matter has any real impact on people’s functioning. Were study participants free from other legal/damaging habits like smoking cigarettes or abusing alcohol?

  • April 30, 2014 at 1:08 pm

    I have no medical knowledge other than that gained over my life, 66 years. However I question whether these studies show cannabis to be addictive. Perhaps psycho-dependency but physical dependency? So areas of the brain have changed but was there any part of the study which tackled outward signs of dependency. Are there signs that the body experiences withdrawal? I, for one, have never experienced any contraindications when I stop using for durations from a day or two to years.

  • April 30, 2014 at 1:59 pm

    We all know what happens when we eat our spinich. Evidence based facts tell us our muscles get bigger.

  • April 30, 2014 at 2:31 pm

    There are some real problems with this story and the sited research. The study of only 40 people is not enough to qualify as a viable test. What were the standards? What were the lifestyle of the participants? What was the ages, the definitions of heavy, the strains used, was it organic or full of ‘bloom’ and ‘hardener’ and other chemicals used in many grows?
    Anything is addicting, exercise, sex, chocolate, tums, etc. There is no physiological addiction to THC at all, no withdrawal symptoms such as there is with alcohol or painkiller or heroin.
    The story is by a guy who owns a very expensive rehab center in Malibu where the rich and famous go for help. Of course he will try to use poorly gathered biased information to say Cannabis is addicting. Google his name and read about his center. I have always respected this publication but the editor should not let a person write a story if they have a financial bias. Come on people, he charges $75,000 for one month. He would love to convince the world that you need his rehab for a Starbucks addiction!

  • April 30, 2014 at 2:54 pm

    I am curious about the studies as well. I am no conspiracy theorist, but I do believe that many opponents of marijuana legalization are proponents of big pharma. I started occasional recreational use in high school and have smoked ever since. I managed to stay employed, obtain higher education (graduate school), keep my home neat and tidy, maintain relationships with friends and family, and function very well as a widowed mother to two young children. My psychiatrist prescribed Trazadone and Klonopin for my anxiety (I do not like how these meds make me feel – akin to a zombie), and wellbutrin for depression. Marijuana alleviates most of these issues without impairing me to a point of not being able to partake in day to day routine and activities. The people of Amsterdam seem to be doing quite well.

    • April 30, 2014 at 4:28 pm

      Are there exceptions to the rule? Certainly. A lot depends on how much marijuana you smoke, how often you smoke it, and how strong a dose you are taking. But the general research holds – that people who begin smoking in their teens are likely to become addicts and marijuana changes the brain of those who smoke it regularly.

      • May 1, 2014 at 10:01 am

        The issue is actually way more complicated with cannabis than any other substance class, because the major receptors are not in the monoamine areas mentioned AND, like all other mood-altering substances, use in the immature brain delays or disrupts maturation. Although I encourage a “straight edge” lifestyle, which I live, for the adult, cannabis (THC to be specific) is distinct from other agents, and has an almost zero risk:benefit calculation, in contrast to all other classes save for xanthine alkaloids. I really must say that you should state this as THC or the endogenous anandamide (AEA) not simply cannabis. This is a fairly complex discussion since unlike opioids or ethanol, cannabinoids, and the endogenous compounds, AEA and PEA, have distinct effects with the PEA and CBD being non-psychotropics. This is not academic, since as an algologist, I feel that the entourage effect of low dose THC with high-dose CBD is hugely effective for bulbar neuropathies such as those seen in MS. K Allan Ward MD, psychopharm geek.

    • May 1, 2014 at 6:43 pm

      I know of some very “high functioning stoners”. These guys are not just keeping up with their peers, in a few instances they are surpassing them by far. Some of them were honor roll types. College graduates.

      • May 2, 2014 at 8:11 am

        There are always exceptions to the rule and the physiology of the brain is less damaged in some people than in others. But let’s be fair – how many Nobel Prize winners, for example, do you know who are also “hard core stoners”? – the answer…exactly none.

      • July 1, 2014 at 8:13 pm

        Mark, I respect your point (yes, yes, I’m answering everything in one night — and it’s good to see you here again). But in this case I disagree. Sure, you can point to a stoner who is also high functioning. But I bet if you took 1,000 stoners and compared them to 1,000 non-stoners, you’d see that if you’re laying a bet, you’d bet against the stoners. You want a case study instead of a population study? Man, I can’t tell you how much better off I am now…

  • April 30, 2014 at 4:11 pm

    This article makes logical fallacial leaps. The author leaps from stating that the studies show that there are changes in certain areas of the brain contingent with age of use onset and the amount consumed, all the way to asserting that it is addictive and dangerous. The research fails to convince. He is thinly veiling his bias. I am surprised that this article was published under the Science of Addiction.

  • April 30, 2014 at 5:07 pm

    I would like to see the methods of how this research was conducted and if they are truthful or if it was like Dr.Heath Tulane’s study(1974) where he claimed that marijuana causes brain damage. He used a method a of pumping 63 joints to a gas mask within 5 minutes for 3 months to suffocate the monkeys that he was experimenting on.

  • April 30, 2014 at 10:12 pm

    I am not a scientist. I have been a psychotherapist for 20+ years. I don’t need to be an addictions specialist to know that I have sat with far too many dismayed parents who thought marijuana experimentation by their adolescents was “normal”, and did not relate the subsequent side effects to pot use: lack of motivation, lags in developmental maturity and emotional intelligence, etc. Years go by, pot use becomes more entrenched, and a generation of under-functioning kids is upon us… kids who do not know how to function well or contribute their best talents in the work place or in relationships. From where I sit, this is a large, looming and growing social concern.

  • April 30, 2014 at 11:41 pm

    Have always encouraged earnest unbiased info but please answer me this. How does “a team of Harvard-led researchers recruited 40 young adults” qualify their findings? What was the duration of the study, did any of these individuals have prior addictive personalities, how is it they could only find 20 young adult marijuana users to volunteer, and what percentage of the legal marijuana user population would that comprise?

  • May 1, 2014 at 3:23 am

    hi appreciate all the work some of you do, as a chronic pain suffer, i feel like i am the enemy, all anyone talks about is how pain med’s are abused. but i know a lot of folks in my shoes and none of us do this, but all legislation. tv talk radio. government etc treat us like criminals, docs are afraid to even write scripts. i ask again, what options are there, truth is some of us will have no liFe without med’s and just because a few criminals abuse dont punish the rest of us, i think we would be better off if those of you that call all of us evil. spent a few yrs in a chronic pain situation, bet you would thinks different. best advice i can give is move to a country like canada, they dont practice :collective punishment: the enemy

    • May 1, 2014 at 10:59 am

      Hi Jack – i completely agree with you mate. what chronic pain you suffer ? mines a lingual nerve

    • July 1, 2014 at 8:17 pm

      Damn, Jack, you make a good point. The chronic pain sufferer has to do *something* to not experience chronic pain. The question is the cost. Can you treat your everyday pain without becoming addicted to opioids? And which is better? I see hundreds of people every year who claim to be in chronic pain, but are just looking for a fix. And I see some who are really in pain. It sounds like you’re the latter. Have you tried complementary therapies like acupuncture and meditation/yoga/massage? If you have and opioids are still the only answer, I hope you find peace. Pain isn’t fun. But neither is addiction.

  • May 3, 2014 at 5:39 pm

    It’s rather depressing that the people defending weed are showing they do in fact have motivation – only to defend their drug of choice.

    • July 1, 2014 at 8:10 pm

      I wish I could just click “like” on this comment. The thing is, marijuana changes the brain. Whether you can still function with your brain adjusted is another question. But absolutely everything written by any reputable researcher shows that pot isn’t a glass of water. It’s real. It’s a drug. And anyone who denies it has an agenda.

  • May 11, 2014 at 12:33 am

    yes its use is dangerous affects personality negatively and reduces power of learning also users get frustrated esily so its good to avoid its use

  • July 1, 2014 at 9:04 pm

    Kinda typical conservative bias undertones. “anyone that speaks about marijuana being ok to use has an agenda”
    (that sounds a bit hypocritical)
    In scientific research there has been many negative /ill effects in products as pharmaceutical, drugs, alcohol. My question is that if cannabis has detrimental effects where is proof such as “cigarettes cause cancer”?

    Gray Matter? (Black matter little sister because no one else knows what the hell that is either?)

    Marijuana plant has been used as far back as the Bible or even before.

    Why don’t you do a study into why “pot drug dealers” and the government want the same thing? That would be a mystery!

    Also Can we please quit calling it “The War on Drugs” and call it the prohibition on cannabis? 🙂

    Prohibition doesn’t work, and helps organize crime.

    Thank you however for the continued studies,of how much better cannabis is for a person, over man made efforts in healing with lab drugs;)

  • March 1, 2016 at 1:20 am

    Hey Richard, Good share.. You have mentioned Good points and it is good to knowledge this valuable information.I appreciate the work you have done.

    Your work will definitely make people realize about the actual truth of marijuana. I am very curious and excited to read your another post.

  • April 24, 2017 at 3:56 am

    this is ANOTHER shameless plug. this time in the form of an argument against weed, which has many medicinal purposes we dont even know about all of yet, as well as beneficial for ptsd and even depression. and the argument is to get people to say “gee i should stop smoking pot-i’m addicted!! now let me go spend 70k$ at cliffside malibu (the writers estate for spoiled adults). shameless plug.


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