from Hacker News

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

by mosiuerbarso on 3/10/23, 2:17 PM with 88 comments

by troydavis on 3/10/23, 2:46 PM
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.
by legitster on 3/10/23, 2:50 PM
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.
by jamal-kumar on 3/10/23, 2:38 PM
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.
by AlanYx on 3/10/23, 2:22 PM
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.
by fallingknife on 3/10/23, 2:27 PM
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.
by dankai on 3/10/23, 2:36 PM
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...).
by bowsamic on 3/10/23, 2:51 PM
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
by Felminor on 3/10/23, 2:28 PM
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.
by thefz on 3/10/23, 4:46 PM
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.
by m0llusk on 3/10/23, 3:04 PM
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.
by Clent on 3/10/23, 2:30 PM
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.
by AnEro on 3/10/23, 2:36 PM
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
by yehosef on 3/12/23, 1:52 PM
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.
by User23 on 3/10/23, 2:27 PM
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.
by varispeed on 3/10/23, 2:23 PM
Totally not biased load of tripe.
by _fat_santa on 3/10/23, 2:44 PM
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.
by Maursault on 3/10/23, 2:26 PM
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.