Long-Term Cannabis Use, Cognitive Decline, and the Hippocampus | Hacker News Reader

Long-Term Cannabis Use, Cognitive Decline, and the Hippocampus

psychologytoday.com

61 pointsmosiuerbarso88 comments

Here's the actual paper. Long-term Cannabis Users Show Lower Cognitive Reserves and Smaller Hippocampal Volume in Midlife: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9426660/

From the abstract:

> We tested the hypotheses that long-term cannabis use is associated with cognitive deficits and smaller hippocampal volume in midlife, which is important because midlife cognitive deficits and smaller hippocampal volume are risk factors for dementia.

> Participants are members of a representative cohort of 1,037 individuals born in Dunedin, New Zealand in 1972–73 and followed to age 45 years, with 94% retention. Cannabis use and dependence were assessed at ages 18, 21, 26, 32, 38 and 45 years. IQ was assessed at ages 7, 9, 11, and 45 years. Specific neuropsychological functions and hippocampal volume were assessed at age 45 years.

> Long-term cannabis users showed IQ decline from childhood to midlife (mean=−5.5 IQ points), poorer learning and processing speed relative to their childhood IQ, and informant-reported memory and attention problems. These deficits were specific to long-term cannabis users because they were either not present or smaller among long-term tobacco users, long-term alcohol users, midlife recreational cannabis users, and cannabis quitters. Cognitive deficits among long-term cannabis users could not be explained by persistent tobacco, alcohol, or other illicit drug use; childhood SES; low childhood self-control; or family history of substance dependence. Long-term cannabis users showed smaller hippocampal volume, but smaller hippocampal volume did not statistically mediate cannabis-related cognitive deficits.

This associative effect is interesting in that there’s not a causal proven relationship albeit many common alternatives have been ruled out. It could very well be the kind of people who partake in weed were already predisposed to losing iq and developing dementia risk factors for some other abstract reason, and we can use weed smoking as a signal of something else being wrong.

Fascinating stuff tho

People will really try anything to make it seem like Cannabis is perfectly harmless even in the face of cold hard evidence, it's laughable.

Its not that hard to believe though. When you have used something for a long while, its difficult to face the fact that you may have been doing something to the detriment of your health. I see it as a coping mechanism.

I really don't understand what the allure of cannabis is. For me, an immediate effect was a decline not only in cognitive ability but also short term memory. Like not being able to hold a thought for more than 5 seconds. How is that pleasurable? It should be no wonder long term use trends in the direction of decline. Of course, for older or termininally ill patients, the pain management benefits may be worth the trade-off, but if the choice is living with pain vs. being perpetually stoned, I think I'd try living with the pain as much as long as I can.

(FTR, I am not against legalisation, so no need to accuse me of trying to take away your drug. I just think we need to make these decisions with caution.)

> I really don't understand what the allure of cannabis is.

Everything that exists in reality, from the observable beginning to the projected end, follows a pattern of abstraction that is exact and single. Drugs give you access to "suspension of disbelief" in experiencing fiction that is larger than reality.

> Like not being able to hold a thought for more than 5 seconds.

Not really an effect of cannabis. Heuristically it's more like the opposite, focusing on one thing for hours. The same way people with ADHD take Adderall.

>> Everything that exists in reality, from the observable beginning to the projected end, follows a pattern of abstraction that is exact and single. Drugs give you access to "suspension of disbelief" in experiencing fiction that is larger than reality.

Thats a fancy way of saying it gets you stoned. You can intellectualize it all you want, but its just words. I can think of any number of ways to "suspend my disbelief": try holding your breath, or slapping yourself silly. Try putting your finger in an electric socket. Really, there's no shortage of ways.

> Thats a fancy way of saying it gets you stoned. You can intellectualize it all you want, but its just words.

This is a forum everything is just words. The reality is that not doing things is X and doing things is X+1, and all of you X people are -1.

> I can think of any number of ways to "suspend my disbelief":

Obviously drugs are better than all of those things. What is the argument there? You can jerk off with a knife too, it doesn't feel as good.

Your description of your experience with cannabis is telling. If you're frustrated with not being able to hold a thought for more than 5 seconds, then that might mean that you went into it with expectations of how it should go, and then spent your time being high trying to retain the "control" you had sober and bring those expectations to reality. This is a common mistake. The good parts of cannabis come from letting go of expectations of control. It's in letting go that hyper focused states or creative bursts can happen.

Not everyone is able to "let go" at will, but some can do it intuitively while others may have anxieties regarding control that must be worked through.

But theoretically, the cannabis should have helped that. I also felt a lot of nerve twitches all over. It might have been too high THC, but it was not an experience that I cared to repeat.

For the kind of experience you are talking about, I would think psychadelics would probably be the better fit.

If you have control problems with cannabis, I suggest you stay well away from psychedelics. Everything that you mentioned regarding your cannabis experience is something that you learn to integrate and eventually move past, to super-creative super-introspective states that you can harness for growth and value. You can learn to guide the experience while you're undergoing it.

Psychedelics are in a different class in that there is no guiding the experience while it's happening. The best one can do is prepare the context (set & setting) and hope for the best. In that sense, they're a lot more difficult to handle than cannabis, but also potentially orders of magnitude more rewarding. But to reap those rewards, I feel that one needs to deploy -if only temporarily- a different model of looking at the world: more like a shaman treating the substances like sacraments, with awe and respect, than a cold rationalist.

Sorry I didn’t make myself clear. I think it’s entirely possible cannabis causes problems. I’m saying this study has successfully narrowed down reasonable associations to make direct cause more likely. But this also means if it is caused by another factor, we can use weed use as a signal for whatever that other factor is with high confidence. It’s multi use in that way which is helpful to establish. It shows evidence that people who are smokers of weed now either are doing damage to themselves or have potentially significant issues they need to address because something is doing damage.

It has drawbacks. No one is saying it doesn't, but now we have a gasp on them.

Like, wait until I tell you about how bad alcohol, sugar, or sleep deprivation is for you...

IQ statistics is pseudo science. Therefore we can dismiss the study out of hand. Soft sciences need to be able to prove their underlying methodologies, and have so far largely failed to do so. They rely on shifting around numbers and cherry picking data to get specific outcomes.

> IQ statistics is pseudo science.

The correlation between IQ and general intelligence is one of the more reproducible results in psychology. Is there a different usage of IQ that you're doubting, or are you doubting that correlation itself?

This doesn't really inspire confidence given the recent reproducibility crises.

Wait, but the IQ/intelligence link is reproducible.

Are you just saying that "most reproducible" is a low bar? (If so, that makes sense.)

Yes, sorry for the lack of clarity. I mean in the same way that infinity+1 > infinity is a trivial difference and only technically true.

Just as something to ponder, this caught my eye:

> The correlation between IQ and general intelligence is one of the more reproducible results in psychology.

and raises the question;

How do you measure | rank 'general intelligence' in a reliable and reproducable manner fully independantly of IQ measures in order to claim a correlation

.. there's just a smattering of chicken and egg there.

I think there's a ton of self deception when it comes to marijuana use. I mean, look with your own eyes and you can clearly see lots of long-term negative effects on users. The studies are only proving what we all really already know.

The same thing was true for cigarettes - even before all of the major studies came out lots of people were able to put together the obvious connection between smoking and lung problems.

Before legalization in many states, even on HN even the suggestion that cannabis was unhealthy could get you voted down. People refused to believe it.

Now that it's legal peoples' objectives have shifted and it's now ok to talk about it. It's a literal example of the stupidity in human psychology.

People don't use logic to make conclusions about the world, they use logic to justify their conclusions so they can fulfill their objectives.

Very hard to find a person who does cannabis on a daily basis and is also fully on board with the fact that cannabis causes cognitive decline.

*Very hard to find a young person. But you find enough people after 10-15 years of using who will tell you they have noticed some effects.

I think it's important to point out that marijuana is certainly less dangerous than alcohol and cigarettes. But it's weird how people try to argue that there shouldn't be any sort of moderation when it comes to weed. Like, even alcoholics won't argue that they shouldn't be drunk all of the time.

The longer duration and fat solubility of canabinoids makes the alcohol comparison difficult. Many people have a glass of red wine with dinner daily, and are not drunk in the daytime, but even very light cannabis consumption nightly seems to result in a permanent low-level stonnedness.

Do you have a source for permanent low level stonedness? TBH that sounds completely made up.

I did not intend that as an empirical observation but rather a mathematical pharmacokinetic result of fat-solubility rather than water-solubility. THC is fat-soluble and so has a higher volume of distribution which drives a longer half-life.

(See Shulgin “The Nature of Drugs” pg 132)

And “constant” would be a better word than “permanent”, as certainly it should go away after some weeks of abstinence.

I use cannabis daily, and I also follow all the studies suggesting cognitive decline, alzheimers, and heart issues, etc. However, having not started till I was in my mid 20's, I do find that maybe I benefited from that cognitive decline with decreased anxiety, more physical energy, and more success in life. But now that I'm in a better place, I do intend to stop for a decade or two though, for the sake of my longevity.

The study didn't mention anything about THC levels of the marijuana, but I would think that would make a big difference. As a general rule, dependence on any substance probably always entails a certain sacrifice to health. Even reliance on a pill to sleep at night has deleterious effects.

>and more success in life.

There's merit in the idea that stupidity correlates with success. Anecdotally you see the correlation among academia and celebrities. Celebrities are richer and happier then academics who are poorer but smarter. Therefore doing something that contributes to your stupidity could possibly increase your success and happiness.

What anecdotally makes you think that cognitive decline contributed individually to your success? I'm curious.

I too value my happiness and wealth over my intelligence, and I would gladly take a stupid pill if such a pill made the trade off between the two attributes.

this is a good argument for its legalisation. The more you try to ban it, the more the allure is. But legalisation should be coupled with early childhood education warning about the harms. It is particulary bad for the developing brain to use it. I fear this has been overlooked, and we are going to see a generational lapse in achievement.

This is true. Banning does work though when coupled with extreme capital punishment. See Singapore.

There is also the argument of whether usage reduction is the objective goal though.

> I think there's a ton of self deception when it comes to marijuana use.

Indeed, as is evidenced by the many comments in this very post claiming the study is bullshit or there's no proof of causality, or whatever else they can come up with.

This is pretty important kind of research. Tons of people are using this stuff medically and while it's obviously a better solution for pain management than long-term use of things that can kill you if they're suddenly unavailable, like opiates, we should still be highly aware of mitigating whatever harms could come from the widely used alternatives. It would also be more interesting to see harm in aspects of things like hippocampal density compared to pain medication than compared to regular alcohol or other recreational substance use. I kind of feel it's unlikely at this point but it could just turn out that people who are prone to losing IQ points faster like to consume more cannabis as well and it's not as much of a causative agent. I would imagine the first thing I want after getting smacked in the head by someone if this was something I did professionally is something to take the pain away. This study could also just be a crock of shit like some others are saying but I don't really feel qualified to judge that.

The only thing that can truly tell with these kinds of studies is another 30 years of data.

Lots of people use it recreationally with the belief it’s not bad for you at all. This kind of research will help to show them that’s not the case.

Everything in moderation :)

I don't know if it will really make any difference at all. Many people consume alcohol regularly and we already know that it's bad for you. I think most people are willing to make tradeoffs, especially when in moderation the negatives aren't really that big.

I doubt most recreational users are using it at anywhere near the same strength or with the same frequency, however.

We're talking the difference between 2 and 200 milligram doses of THC here in terms of how it affects people on these levels. One comes in a soda at the store down the street from me. The other you can't get like that and might send your average recreational user to the hospital with a panic attack.

I'm wondering also if one of the big factors here is oxygen deprivation. These sound kind of like the same kind of numbers of cognitive decline that you see in air pollution, maybe just generally clogging your lungs with smoke could be comparable.

With the legalization in a lot of states people are consuming ridiculously strong amounts of THC these days and it’s only getting legalized in more places.

What's most interesting about this article IMHO is that these results were found with "long-term cannabis users" defined as those who use "typically 1-4 times weekly". That seems like relatively casual use.

Author obviously has a conflict of interest. He fails to acknowledge that correlation is not causation and that these studies fail to take into account other variables that could influence the outcomes.

I read the article and did not see anything that would qualify as a conflict. Correlation is not causation only on its face, which is why researchers compare their findings against control groups.

> a psychiatrist who specializes in addiction medicine.

And typically their are missing confounding variables.

I don’t think you’re using conflict of interest correctly. You’re saying here the author has secondary motives, such as being sponsored by an anti-weed org or something, which they would have to disclose in their own section (as per basic academic standards).

You might want to instead if you want to criticize the research say the authors clearly have a personal agenda or bias.

This is par for the course. When anyone suggests that weed may not be beneficial to your health people who consume it tend to get very defensive.

It is common for people working with addiction to demonise drugs, so that they can have stream of scared patients lined up.

I don't think they have any shortage of patients in rehab. There is already a steady stream of them. Rehab counselors are often former addicts just trying to help others live through what they did. It is not exactly a way to get rich.

> correlation is not causation

True. But then there’s something that makes you stupid and makes you use cannabis at the same time. This is as bad as just cannabis making you stupid.

It's the same situation as observing that people who take pain killers have headache, therefore pain killers are causing headaches.

This is the level where OP's article is at. It's baffling that people upvote that drivel.

That highly depends on your frame of reference, I suppose. In most of Germany that would be considered fairly 'heavy' use already, whereas most of the West Coast would probably consider that to be rookie numbers.

I had roommates at UCSC where 1-4 times a day was a minimum.

Dude eventually quit cold turkey for a 6+ months. Also quit booze, coffee, and tobacco, dropped out of Uni and hung out at an uncle's cabin in the mountains, real Walden Pond sorta stuff. Did him a world of good, but then he got a job w/ a FAANG and went back to the "smoke two joints" routine again.

It's pretty shocking how many people I know who are essentially high 24/7.

If you look at the description of the cohorts you'll find that most of the people classified as long-term cannabis users were using cannabis quite a bit more frequently than that (median ~300 days per year). It just happens that the analysis here split people into boolean subgroups rather than trying to quantify a dose-response effect (as the primary outcome; dose-response effects are claimed but not emphasized).

I would be most interested in seeing a correlation with sleep disturbances. Some cannabis users claim that they smoke weed to help with sleep disturbances; critics argue to the contrary that persistent cannabis use may cause sleep disturbances. Chronic sleep disturbances are known to correlate with a variety of negative outcomes, and the use of sleep-inducing drugs is known to correlate with a variety of problems as well (including the great boogeyman, all-cause mortality).

From my own perspective, I stopped smoking weed last year, but I don't think the overall change has been very noticeable. The use of means can distort perceptions when distributions are not symmetric. Notably, my sleep habits aren't great right now, though I'm working on it.

I smoked weed constantly in college, and when I stopped, it was like a fog lifted. Its danger was comically exaggerated in the anti-drug propaganda they force fed to kids in the US for so long that a lot of people have a reactionary tendency to assume it's harmless, but they will soon be proven wrong. Still has nothing on America's number 1 hard drug, alcohol, though.

Yeah, I kinda know what you mean by fog. I have a "low key" addiction to weed because I'm a bit emotionally dysregulated and weed helped with that. So, when I'm struggling to cope I sometimes wish I had weed at hand.

However the fog thing is real. I noticed it on myself when I stopped too.

It did without a doubt help me live a somewhat more normal life than if I hadn't been using it at the time.

However eventually as I got better (in general, still got acute episodes), the fog/downside outweighed the benefits.

I think it should be studied more as a form of medication. Maybe smaller doses and administered orally, as to avoid the negative side effects associated with smoking or vaping it

I've found it's possible to get high every night, and be clear headed and functional in the morning.

A weekend of heavy smoking and edibles can leave me feeling a bit sluggish on Monday. But also refreshed for the rest of the week.

Ditto. I don’t smoke cannabis that is bred to be high in thc, because I prefer a light effect. I use a dry herb vaporizer and don’t have any issues engaging in deep thought work in the morning.

My main concern with long term use is dream suppression. So I do take breaks frequently. Also I think it’s not a good for developing brains <25y. Cannabis is great as medicine for colds, flu, aches and a lot of more serious conditions and chronic conditions.

In the realm of things that I think the government needs to protect us from, I think cannabis prohibition is completely absurd and insidious. We barely talk about alcohol addiction and god forbid we reckon with prolific Tylenol and NSAID abuse — both of which have acute toxic effects on the body.

The deciding factor for that next-day sluggishness, in my experience, has been whether or not I fall asleep while still noticeably under its influence. If you wait it out and then sleep near the end of the come-down, you may avoid it entirely. But then, I never use it to sleep, so YMMV.

Your experience matches mine almost exactly.

Look at the sample sizes and the demographics (https://imgur.com/a/LG5vVMF) of the groups the study (https://moffittcaspi.trinity.duke.edu/sites/moffittcaspi.tri...) compares. Also look at the publication bias of the first author (https://scholar.google.com/citations?view_op=list_works&hl=e...).

if you mean the very small mean iq difference at baseline, that is hardly a significant concern, here especially in a longitudinal design. As far as publication bias, do you mean expert in his/her field?

There is such a taboo around discussing this that even if you present a lot of people with an extensive meta-analysis showing that there are negative effects people will totally brush it away and call it BS. It seems we have swung way too far in the opposite direction from "weed is really bad and makes you crazy and paranoid" to "weed is totally fine". Naturally the truth is somewhere in between, though so many people seem totally sure it's the latter

What's that? '. Their cognitive decline may have altered employment opportunities for which they were qualified, but they were in no way demented. Yet.'

Who writes like that?

Also I have insomnia and ADHD and I'm pretty sure weed does help and allowed me to do more not less.

Without it I'm super tired already at Thursday.

And yes I lived long enough without it and it was like this before my weed use not after.

Interesting. I have ADHD and find that smoking weed makes my symptoms noticeably worse. Depending on how high I get, I find myself largely unable to focus, or even to complete thoughts without becoming distracted. This seems to persist after I'm no longer high -- even many hours after smoking I still find myself less able to stay on task.

If you're of the hyperactive type I could possibly see some benefits? As an inattentive and non-hyperactive type it's hard for me to imagine weed helping very much.

I find the same thing. Cannabis just makes me lose my train of thought within 5 seconds. It is very irritating.

The one thing I found to help the most is excercise. Even moderate daily walking, but the more you do it, the more benefits you get. There are actually endorphins released that mimic a high the natural way.

I'm very restless normally.

Enough weed and I'm not keeping myself awake.

But I only eat a cookie before bed

I have shaky hands, and a shot of alcohol is one of the recommended ways to treat them. This doesn't mean that alcohol has no downsides though.

Acknowledging that something has negative long term effects doesn't mean that you have to stop using it, it just means that you should weigh those effects into your mental cost-benefit analysis.

Excercise is also great for ADHD. Even a 2-mile vigorous walk every day. And it actually improves your health.

Anecdote time: A couple of late 30 to early 40 year old friends smoke constantly since the '20s. And I mean every day, multiple joints. They claim their life is normal, I claim that... it shows somehow.

From senseless paranoia to being reclusive, and sometimes being very late/slow in grokking things, they are very different from the rest. Even from casual, weekend smokers.

I think that you can't expect to smoke 5 to 8 joints every day and lead a normal life past your '20s.

It might be interesting to give this more context. Does five points of IQ loss in later life actually change outcomes? And what about the rest? In my experience older cannabis users tend to be more centered, pleasant, easygoing, and are better at retaining their social support networks over long periods. My cannabis use has made my life tolerable, so if there really is a loss in IQ then that might not be such a bad price to pay. Comparing my work history with others my age it really isn't clear that my long term regular cannabis use has made any negative change that isn't visible in others.

It seems like these studies are mostly about confirming bias. People who are judgemental and don't like cannabis can confirm that cannabis users are bad and slow and degraded and so on. But we are still here we need to share the world somehow so it might make sense to think about balance and trade offs rather than only ever keeping the emphasis on no, no, no, you might degrade some of your capacities.

This isn't standalone "five points of IQ loss", this is "brain volume loss culminating in five points of IQ loss among others". 12% hippocampal volume loss is half of what happens in Alzheimer's, it's nothing to scoff at.

Does this imply that cannabis is never worth using and we should "protect" people from it? Probably not, but it's sorely needed in light of the "weed is harmless and a medicine for many" narrative that's getting blasted everywhere.

This is not a primary source of anything related to psychology.

This site is article marketing for people in the mental health field.

The primary motivation of the author's is to self promotion.

Here's the full text of the paper it's covering (cited as footnote 4):

"Long-term Cannabis Users Show Lower Cognitive Reserves and Smaller Hippocampal Volume in Midlife": https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9426660/

You might say that article is, in many ways, a puff piece.

Maybe, but there’s no smoke without fire.

It can be difficult to weed out the useless information on the subject.

I find that to be a chronic issue.

I also wonder what their lifestyles are in general, and if it would have an effect. I feel like weed puts my brain into autopilot to a degree and makes me 'okay' with w/e I am doing. So recreational usage I could see making you 'dumber' cause weed lets you feel okay doing nothing and doing nothing is a good way to be dumber

My anecdotal opinion for someone that smokes a lot compared to their long-term cannabis users, maybe once or twice a night vs 1 to 4 times weekly. I'm late twenties have been smoking since my early twenties, obsessed with brain optimization and min maxing performance etc. I feel like I've gotten smarter in some areas and dumber in others, which lines up with how weed affects the reward circuits of the brain imho. So I've been using it as a reward for doing stuff I otherwise would be uncomfortable with trying, like a new project or new hobbies; anything worth doing is worth doing poorly. So I think it has helped me get smarter programming and developing intuition on some areas, but since I have avoided writing like the plague it's gotten terrible to be honest. Personally it feels like it just tunnels you in further to what ever you are doing, and possibly makes it harder to stop doing it even not high

> anything worth doing is worth doing poorly

Ha! That’s great line.

Physical excercise can give you many of those benefits too. A good strenuous workout or run will give you a high without any of the harms.

That's why I also lift and do jogs! That's why I'm interested in the lifestyle peace because I have a pretty healthy lifestyle outside of smoking weed. I think I could be doing better micro nutrient wise and get a better omega and mushroom stack rather than w/e veggies are on sale lol

I think that part of the suspicion of research like this comes from years of complete lies about the dangers of cannabis. The fact that is still classified as a schedule-1 drug even though we know that it's nowhere near as dangerous as it was claimed.

It's also important to note what affect cannabis has on the pharma-industries. It's a "weed" that can help cure a huge variety of serious issues with far less cost, side-effects and risks than prescription drugs. Given the influence of the big-pharm on medical publications and research, I assume some people will be suspicious of any research which says anything bad about something that might affect their bottom line.

I'm not saying these arguments are valid for this article, just explaining another angle why some people might be suspicious.

This is a huge effect size especially in the tails. I wish the article talked about the control groups though.

I predict a number of addicts will be triggered by this research. We saw the same effect when we found that even light drinking is measurably harmful. If your first reaction is to get upset and defensive there’s a good chance that you have a problem.

They'd be triggered by the results, not the research.

and the first to claim that the author is biased.

Totally not biased load of tripe.

My issue with this study is they based it around IQ points. I feel like IQ is a very bad measure of cognitive ability outside of determining if someone is competent of not. And the fact that it only went down by a mean of 5.5, I feel like that small of a decline could be attributed to someone just having a bad day or being a little groggy when they took the IQ test.

Had the measured brain waves or brain activity it would be one thing, but I feel like an IQ test is just not satisfactory for a study like this.

5.5 is a massive decline in IQ.

Have you got any reason to think IQ is a bad measure of cognitive ability? And what makes you think 5.5 points is small? The average is 100 and a typical standard deviation is about 15; one third of a standard deviation looks pretty big to me.

> And the fact that it only went down by a mean of 5.5, I feel like that small of a decline could be attributed to someone just having a bad day or being a little groggy when they took the IQ test.

How does your theory explain that the results were particular to certain sub-groups? That is, the 5 point decline was only associated with long-term cannabis users.

(Is your theory that long-term cannabis users are more likely to "have a bad day or be a little groggy"? That would explain the sub-group difference, but it seems pretty similar to the author's results.)

This just in: drugs make you stupid. Alcohol lowers IQ. Watching television lowers IQ. The decline in IQ reported sounds like it's within the margin of error. 10,000 years or more of cannabis use, and it is shocking we are only learning about it now that pot makes you stupid.

Reply on news.ycombinator.com