Can Weed Really Shrink Your Brain?

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Brain, Podcast

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Click here for the full written transcript of this podcast episode.

A few weeks ago, I talked on this podcast episode about whether THC can cause damage to the grey matter in your brain.

But, frankly, I spent very little time addressing the matter on that particular show, so in today's episode, I'm revisiting the topic of THC, brain damage, liver damage, myths about marijuana, CBD, smart drugs, nootropics and more with Dr. Andrew Hill, Lead Neuroscientist at truBrain, and one smart cookie.

During our discussion, you'll discover:

-Why left-handed people are more sensitive to chemical stimulants…

-The truth behind the evidence that THC can shrink the brain…

-The important differences between THC and CBD…

-How Dr. Hill can “reset” tolerance to marijuana using neurofeedback in his clinic…

-If there is a deleterious effect of THC on the liver or other organs…

-How to map your brain and change your brain using neurofeedback…

-Little known smart drug ingredients such as oxiracetam and centrophenoxine…

-And much more, including a killer giveaway at the end of the show!

Resources & studies cited in this episode:

Decreased grey matter but increased connectivity (not controlled for SES):
More recent and much larger study that failed to find grey matter volume changes:
And a summary of another study that found decreased volume, and the two studies that refute this:

Peak Brain Institute

Pocket Neurobics

Heart Rate Variability (HRV) Training

TruBrain drinks and capsules 

Previous episode with Dr. Andrew Hill on smart drugs vs. nootropics

Water soluble CBD

Do you have questions, comments or feedback for myself or Dr. Andrew Hill? Leave your thoughts below and one of us will reply.ttp

Ask Ben a Podcast Question

26 thoughts on “Can Weed Really Shrink Your Brain?

  1. Megan says:

    I found this podcast very interesting and I am very interested in the brain and how things work.


    I have been very interested at the effects of raw nutmeg for anti-anxiety and how it increases feelings of euphoria, empathy, creativity and time dilation. Similar to cannabis but different. I have taken it myself and experienced these benefits and suffered no severe side effects with only 1-1.5tsp of RAW ground nutmeg. Even though there are horror stories in forums of ill-effects, I have never had them and it feels definitely nice–so I assume they didn’t consume in the correct way/amount. However, my research leaves me concerned at the long-term side effects. Nutmeg is touted for helping improve memory, like in an article from or E-oil companies, and yet the long term effects on memory may not be healthy. From my research, Myristicin is most likely an ANTIcholinergic and blocks acetylcholine at AChRs which may be linked to memory loss and loss of empathy in the long run…?? While it may improve memory and creativity while under its influence, it may be creating a lack. Although, this site proposes that it may promote procholinergic activity.(…/5366 ) That leads me to think maybe it’s the amount that matters? (Perhaps like alcohol, a little would be a stimulant, but a lot would be a depressant.) But most places I find say it’s an ANTIcholinergic. Myristicin may be a slight MAO-I, and a precursor for MMDA which is similar to ecstasy (MDMA). From what I understand ecstasy can increase euphoria and empathy but will leave the brain and body lacking in those things in the end, and I have heard, “burning holes in the brain.” I do love the effects of raw nutmeg and have never experienced the negative side effects people warn about all over the internet, but my research is leaving me weighing the risks and whether or not it’s worth it for brain & body health on the cellular level. (I don’t want to be giving myself Alzheimer’s…) I wish some more research would be done on this–there doesn’t seem to be much information or attention to it on the internet and it’s totally legal. I would love Dr. Andrew Hill’s or anyone else’s opinion. (I think Dr. Andrel WEIL did some studying on it.)


    In my mind, consuming cannabis is “better” than smoking because I assume I am getting more of a whole-body benefit, and avoid the inhalation of smoke. I would rather consume cannabis (than the more socially acceptable alcohol) for health reasons, and have done so only at the beginning of the weekend and in 1/4th doses (I’m only 93lbs & 4’11”!). It is very pleasurable to me because it really stimulates my brain and emotions and I love creating, experiencing, thinking, and learning. Even though I live in WA state, I am afraid of the ramifications of getting drug tested at my workplace and it being an issue with them. So that sucks and of course leaves me not knowing what to do. Probably not risk it. >:( (I am a certified health coach.) :p

  2. Manuela says:

    Unrelated to the main topic, sorry about that, but talking about products from one of your sponsors you mentioned bananas, at the beginning, as ”potentially” being nonGMO. But, since bananas have been engineered to be seedless, aren’t they all GMO, already? Sometimes, I find it very tricky to understand exactly what these ideal-health-produce labels actually mean. I’d love to know more about this. Maybe it would be a good topic for some future podcast, if you haven’t covered it already.

    1. Call it into the podcast –

  3. Kurt says:

    In regard to CBD “oil,” is there a marked difference in what it’s extracted from, whether hash, indica or sativa or ruderalis(hemp), in terms of efficacy, potency? There are marketing companies online advertising CBD oil “legal in all 50 states.” Most indicate their oil is from hemp, hence legal.

    I reside in a state that hasn’t yet legalized medical marijuana, so my options are limited. Interested in CBD, but unsure of whether HEMP CBD medicinal claims are valid.

    If valid, can anyone recommend guidelines, what should I be looking for?

    1. Kurt, you should read this, and let me know if you have any questions…

  4. cavemanMC says:

    Hi Ben, epic podcast, epic book. You're a treasure trove of useful information for me! I have a question about THC usage.

    When smoking THC, I find I frequently suffer from really cold hands and feet, and a bit of dizziness (low blood pressure – this carries on in to the following day). Is this something one would expect, as I speak to other people and many others have the same experience, but its not normally bad enough to mean one stops using it, its just annoying. For me I query whether its good for me to use it given it does this to me.

    To give you a short background on me: I don't use it frequently, maybe twice a month for one evening just to chill out from a stressful lifestyle. I have found nothing that relaxes me like THC and CBD. These ailments are things I suffer from normally, and have not had much success figuring out what causes them. I have previously had adrenal fatigue, according to adrenal saliva tests, but my latest saliva test indicate my cortisol is back and DHEA are back in the normal range, but testosterone is still low.

    1. I have never heard of a vasoconstrictive effect of THC like this, but one thing you could try is experimenting with Indica vs. Sativa vs. hybrid…different strains can have differing effects. The website Leafly is my favorite site for exploring strains.

  5. bryangoestoperu says:

    Amazing podcast as usual Ben, great to hear you and Andrew Riff on brain hacking and Nootropics.

    My question is that given the research on things like coconut oil, lion's mane and psilocybin and their effects on brain health and neurogenesis do you think it's plausible to harness these foods and fungi to reverse dementia / prevent alzheimers ?

    Hypothetically if you or a loved one was diagnosed with Alzheimers or neurological disfunction of some sort what would be your ideal protocol from a food and supplementation stand point for best dealing with that situation?

    1. We recently discussed reversing brain damage in podcast But when it comes to Alzheimers there is a whole different set of protocols, including photobiomodulation, ketosis, and some of the same foods/supplements used for brain hypoperfusion. This would actually be a good question for you to call into the podcast!

  6. e_h says:

    Ben, I want to thank you for doing this follow-up podcast. It's rare that something compels me to take the time to comment on a podcast…in fact this is the first time I have done so. About 3 years ago I began using medical cannabis for a sleep issue. I had only used it twice in my life prior to this and believed all of the propaganda that I had heard. Prior to using it medically, I did a lot of research on my own and was shocked to learn how much we have been lied to. I am not some sort of hippy or member of a fringe group. I have an MBA and an undergraduate degree in an allied health profession. If you saw me walking down the street you could easily mistake me for an accountant…yet I use cannabis every single day. I have suffered no ill consequences in my professional or personal life. I want to commend both Ben and Dr. Hill for being open about their own use of cannabis as it helps to dispel the stereotypes about who uses cannabis.

    I listen to a lot of podcasts and I can say that the Ben Greenfield fitness podcast provides extremely valuable and practical information all for free which is awesome. This specific podcast is just another example. Thank you both for taking the time to record this podcast!

    1. Thank you!! And feel free to leave a review in Itunes, we always appreciate those!

  7. hayrisdnet says:

    Any comments on '40 years of zen' ( I think this is a feedback system as well, but pricey?

    1. I haven't done it. Dave obviously swears by it, but I can't speak to personal experience…yet! But stay tuned for an interesting blog post on how freediving and mammalian dive reflex fits into this equation.

  8. Erik Rokisky says:

    Hey ben, loved the show! I am curious to hear yours and Dr. Hill’s thoughts on the effects of combining THC, caffeine, and smart drugs for studying purposes. I have heard that THC can enhance flow state, but does affect short term memory. I have final exams coming up and was wondering what you think about using this stack to study. Could the smart drugs cancel out the short term memory loss effects from THC? In addition, would love to see you on the Joe Rogan Experience ! You and Dr. Hill together would make an amazing episode. Thank you for all the information you put out. You are a role model in the health and fitness field. Thanks again!

    1. CBD is the one that you would want to combat the memory issues with THC. I explain why here:…

  9. No_Free_Will says:

    Do any of the ingredients improve cerebral blood flow? I would think that in order for the compounds/micronutrients to be effective they must reach the target receptor, cell, or tissue in sufficient concentrations.

    Also, why are there no herbal constituents? Herbs have the advantage over semi-synthetic compounds in that there are multiple compounds that work synergistically to prevent side effects and create additive and multiplicative physiological effects. They also have the advantage of hundreds, even thousands, of years of use by traditional cultures. I would recommend Bacopa monnoeri, Mucuna Pruriens, Gotu Kola, and Hericium erinaceus (Lion's Mane mushroom). I take a combination of these as well as other micronutrients and I have found the effects to be dramatically more significant than any of the racetams/choline derivatives for almost any metric relating to cognition (working memory, recall, recognition, relearning, focus, etc.) Thanks for an awesome show! Ben always delivers.

  10. Eric says:

    I’m completely new to THC and CBD consumption as I was always raised with the “weed is bad for you” stigma.

    Where do I start?

    1. bryangoestoperu says:

      The Emperor Wears no Clothes by Jack Herrer and The Benefits of Marijuana by Joan Bello are two great books that will get you going.

  11. aaron900 says:

    Thank you for getting Dr. Andrew Hill on to revisit this topic as I requested. His neurofeedback training sounds useful to me, the main reason I use cannabis as much as I do currently is to self medicate ADHD(not that I like that label, so I would usually say short attention span and scattered thinking). I will always use some cannabis, but I could reduce the amount it would save me a lot of money. Can you tell me if Dave Asprey's neurofeedback training would give me a similar effect, I would rather only pay for one and was already thinking about that one. Also what are the prices like for Dr Hill's training?

  12. silber999 says:

    Thank you, Ben and Dr. Hill, for such an informative podcast. Ben, you've touched on THC, CBD, neurofeedback and smart drugs in other podcasts in the past (though perhaps not the same podcast), yet the new content you elicited in your interview with Dr. Hill was so enlightening. I appreciate Dr Hill's frankness regarding the efficacy of some of the popular neurofeedback technologies on the market, his personal experience with various substances, as well as your own. Everytime you interview Dr. Hill, the two of you peel back another layer on how we can achieve optimal brain performance. Next time you interview Dr. Hill, and I hope there will be a next time in the not too distant future, I would love to hear his thoughts on nootropic supplements for assisting youth with focus issues (ADHD diagnosis or not). And by youth I mean teenagers. Dr. Hill touched on the benefits of acetylcholine for focus. Also, I wonder, Ben, what your thoughts are on nootropics for kids. Thank you again!

  13. johane777 says:

    This was an amazing podcast, Ben! Thanks so much for having the courage to be honest in all your podcasts! This podcast in particular has really opened my eyes and explained why I've had issues in the past…being left-handed and I used to have high blood pressure (though I've tamed it drastically with the right nutrition for me) like Dr. Andrew Hill. When I've tried THC and CBD it's scared me so so much…I actually thought that I was going to die. But now that I understand that my brain may be more sensitive than average, it all makes sense! For sure I'll try again, when I get the courage…and when I've done a bit more research. I'm one of your regular listeners, and I love the work you do! Again, thanks so much!!!

  14. colezy99 says:

    Another great podcast Ben! You never fail your audience asking great questions and quite often the same ones coming to my mind. There is so much confusion between THC and CBD and I really appreciate knowing the very important differences, I can't wait to get my hands on your water soluable NatureCBD product and experiment with it. Looking forward to more great info to come!

    Scott from Saskatchewan

  15. Lia Parker says:


    Great show…I wish I could have an hour to talk to Dr. HIll. I started experimenting with nootropics because I knew from various trauma in my life, my brain was effected. Phynalpiracitam has seemed to make the best nootropic so far. I have tried Noopept, Modafinil and paracitam. I am attempting to add choline to the mix as I understand it is needed to support the use of the nootropics. I am having a hard time finding dosage. Could you give me any insight or direction regarding this?

    Secondly, I have read that phenylparacitam can become less effective over a short period of time and cylcing use it what I need to do, yet in the show you said paracitam has a reverse tolerance effect? Is it because it doesnt have the phenyl group on it?

    I took organic chem years ago in college….needless to say I am in my 50’s…but I was able to keep up with most of your discussion and it made me feel like a bad ass old lady! LOL

    These nootropics have been a life saver for me, as I struggled to participate in life.

    Thanks so much. I appreciate your time, as I know it is valuable.

    Lia Parker

    1. andrewhillphd says:

      Hi Lia

      Exactly – phenylpiracetam is not sustainable, and acts more like a stimulant (both in effects and in how it habituates / develops tolerance) so isn't useful day after day.. A choline source should help regular piracetam work better. We use Alpha-GPC or Citicholine in the versions of truBrain.. one of those at a few hundred milligrams in the morning with your 'racetams is probably sufficient.

  16. DavidD77 says:

    Kindest Regards,
    David Doherty

  17. DavidD77 says:

    Hi Guys former medical resrarcher,C.PT, Massage therapist,Reiki,Naturopath etc etc before numerous severe chronic illness and in wheelchair wife now ft cater but using with great success like millions of people "The Entourage Effect" and medicinal success (refer Hebrew University Israel MMJ Dept research (first isolate many medical cannabinoids) and evidence at on treating ALL diseases including latest stage brain tumors shrinking using 90-Day High dose Medicinal 100mg pday CBD Oil 4weeks before introducing Medicinal THC Oil combination again working up to 100mg by 90-day working on many many diseases untreatable by Chemo etc so wish could upload my research ECS receptors essential fighting all diseases minimal side effects if Certificate of Analysis (COA) provided (like do) totally essential bind CB1 CB2 receptors with "proper" CBD/THC Oil..totally different and much more medicinal value esp if combined with Alpha-GPC+Noopept or Aniracetam/Oxyracetam (infact) most nootrpic stacks for Coline Precursor,Tumeric as Cox-2 inhibitor and increases absorption, MCT in mucus gland mouth increase bioavailability etc ect

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