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Meta at Science News reports on a new study (DOI: 10.1073/pnas.1516648113) still paywalled at PNAS:
Marijuana is used more than any other recreational drug, with recent trends toward greater social and legal acceptance in some regions. Concerns remain, however, about a possible causal relationship suggested in scientific studies between marijuana use and decline in IQ.
A new study from two longitudinal studies of twins, examine the link between marijuana use and IQ using data from more than three thousand individuals from Southern California and Minnesota.
The study by scientists from UCLA and the University of Minnesota focused on three criteria they proposed as measures for evidence of a direct causal relationship between marijuana use and cognitive decline.
- If marijuana use causes IQ decline, as opposed to merely being associated, then poor cognition scores should only be evident after use begins, and not before.
- If a causal link exists, a dose-response relationship would be expected.– that is, higher decline with heavier marijuana use.
- finally, if the relationship is causal, then the association of marijuana use and IQ decline should remain, even after accounting for genetic and social factors.
In tests of abstract reasoning and problem solving associated (called "fluid intelligence") showed no significant differences between uses and non users.
[more]
The study did find decreases in ability among marijuana users compared to non-users in the ability to use previously learned knowledge. (Vocabulary and Information retrieval, or so called "crystallized intelligence".)
The authors noted, however, that the baseline IQ scores of eventual users were already significantly lower in the affected areas.
Here, marijuana use does not precede cognitive decline, and they point out prior evidence that suggests other factors such as behavioral disinhibition and conduct disorder that may predispose individuals to both lower IQ and substance use.
(So criteria 1 above was not met).
The study also found no relationship between heavier or more frequent marijuana use and the magnitude of IQ decline.
(Criteria 2 was not met).
Finally, the authors examined the effects of outside factors associated with IQ decline. They found the decrease in Vocabulary scores was reduced in one study and "completely eliminated" in the other when adjusted for participants who self-reported binge drinking and use of other drugs.
(Criteria 3 also failed).
The authors conclude that taken together, the results provide "little evidence to suggest that adolescent marijuana use has any direct effect on intellectual decline".
(Score: 1, Interesting) by Anonymous Coward on Tuesday January 19 2016, @08:25PM
I guess that means the two young gentlemen in the Community College classes that I taught were just terminally stupid rather than severely affected by the impressive/depressing quantities of marijuana that they used.
That's a shame.
I preferred to think they were merely impaired by the external influence of the smoke, rather than by some inherent deficiencies. Nice enough kids, but absolutely INSISTED that marijuana didn't have any adverse effects on them. They'd make that point several times an hour, whether or not anyone asked.
(Yes, anecdote is not evidence. One AC post should not be taken as proof of anything.)
(Score: 5, Interesting) by Anonymous Coward on Tuesday January 19 2016, @08:32PM
1. It could affect short term memory
2. Stupider people more likely to hit the bong
3. Weed users more likely to be binge drinking, which causes real damage
The study shows how to not be a statistic while using weed, except that daily heavy weed smokers with memory impairment are going to look stupid to most people even if the damage is not permanent.
(Score: 3, Insightful) by VLM on Tuesday January 19 2016, @08:58PM
There's probably an aspect of self medicating for depression or WTF mental issue, which makes the user feel better but just as ineffective at the game of life as before smoking up.
Observation from my youth is the weed never did anything too bad, but it did mess with people socially; that dude being a bad influence to hang out with isn't fixed by getting stoned, etc. Failing a class, feel bad, some would study, some would smoke up, guess how that turned out.
(Score: 2) by kurenai.tsubasa on Tuesday January 19 2016, @11:39PM
I think you're running into the causation-correlation mix-up that allowed previous studies to show cannabis usage having an effect on a variety of outcomes for individuals. (Things like negative outcomes wrt relationships is a bit different ball of wax.) The nature of the mix-up are that people who are prone to having lives that are messes also have an easier access to cannabis flower.
Right now I'm self medicating with alcohol because SSRIs I've found are worse than ineffective. I guess they work for some people but not for me. When I have an easy access to cannabis for a prolonged period of time, I tend to drink far less and make better choices in general, like jogging a mile or two before work every day and doing strength exercises after work every other day. (Also little things like preparing a homemade lunch instead of eating junk. I'd prepare 5 or 6 300–400 kcal lunches/meals on Sunday for the rest of the week and put them in the fridge.) I don't think I'd felt healthier and actually was healthier according to the numbers before or after that period of my life.
I'd love to be able to figure out what cultivar works for me best by stopping by a gas station (or dispensary if we must) on the way home and trying different ones until I find it. I'll know I've found it when I start thinking I can comprehend fifth dimensional geometry. Also of course no psychoactive compound is without side effects. I imagine heavy, daily use has to have some effect vs. control. These days I'd probably look for vaporizer juice, but I've got a sneaking suspicion it isn't just THC that was helping me. There's a menagerie of cannabinoids that act on the endocannabinoid system in different subtle ways at different strengths in different cultivars.
I mean, of course somebody is a dumbass if their response to failing a class is anything except studying harder and seeking out resources to help them learn the subject matter. I don't think cannabis flower has much to do with their being a dumbass. Plenty of dumbasses find ways of being dumbasses without cannabis. Apply same argument to World of Warcraft for example.
Well, no, scratch that. There are way better games for dumbasses to waste time with!
(Score: 1, Interesting) by Anonymous Coward on Wednesday January 20 2016, @01:47AM
I started taking Fluoxetine (Prozac) about three months ago -- I guess I'm lucky because it really works for me. I wish I had tried it 15 years ago. I was worried it would make me stupid, but the opposite is really the case. I used to work on hard projects as a way to distract myself from my self-dialog/excessive negative thoughts/anxiety. Now I work on the same projects for fun. It's a difference that makes life seem worthwhile rather than a chore.
I know they don't work for everybody, and I'm empathetic toward you because they don't work for you, but for anyone who has been living with a constant barrage depression and internal negativity, it's worth a try. I was at the point where I really felt like I just wanted to die and figured I should at least try medications before buying a tank of nitrogen gas. Now I wish I would have tried prozac years and years ago, but, at the same time: "whatever". One thing about prozac, it has helped me build up what I consider a healthy sense of apathy -- if you care too much about everything you do always being perfect, and beat yourself to a pulp for the slightest failures, life is a horrible torture. It takes a little apathy to make life good -- some people will understand that.
(Score: 3, Insightful) by kurenai.tsubasa on Wednesday January 20 2016, @03:27AM
My roommate has actually had great success with Zoloft after being burned by Prozac. I think each individual needs a tailored healthcare solution when it comes to depression.
Many of us are depressed for vastly different reasons, and that would I think at least imply different cures. I'm happy for you! Huge success!
(Score: 0) by Anonymous Coward on Tuesday January 19 2016, @09:22PM
3. Weed users more likely to be binge drinking, which causes real damage
Which has little to do with the marijuana itself, and is more about the choices of the users.
The study shows how to not be a statistic while using weed, except that daily heavy weed smokers with memory impairment are going to look stupid to most people even if the damage is not permanent.
It's foolish that some people equate intelligence to memory. You need to be able to retain information to some extent, but strong critical thinking skills are far more important when you're talking about intelligence.
(Score: 0) by Anonymous Coward on Tuesday January 19 2016, @09:55PM
Memory is needed to function day-to-day as a human being. You are much less useful if you can't function socially due to vocabulary problems or have to look up information constantly.
(Score: 0) by Anonymous Coward on Tuesday January 19 2016, @10:00PM
Memory is needed to function day-to-day as a human being.
I said: "You need to be able to retain information to some extent"
I still say that it doesn't have much to do with intelligence. There are serious diminishing returns here. A person who can memorize everything instantly is not necessarily a person who can make amazing innovations; they are different abilities.
(Score: 0) by Anonymous Coward on Tuesday January 19 2016, @10:29PM
Yes, I know, you said "I've drawn this arbitrary and blurry line, and I will move it wherever I need in order to weasel out of any counter example presented to me."
(Score: 0) by Anonymous Coward on Tuesday January 19 2016, @10:50PM
No, it's more like I acknowledged that you need to be able to retain information in order to function. Good job missing the larger point. Not everything is about weaseling out of something else.
(Score: 0) by Anonymous Coward on Wednesday January 20 2016, @02:40AM
Sagan, Feynman, Gould [famousscientists.org]
-- OriginalOwner_ [soylentnews.org]
(Score: 2) by ikanreed on Tuesday January 19 2016, @09:53PM
Well, it definitely does substantively affect likelihood of psychosis. Psychosis can be far more debilitating to classroom achievement than fluid intelligence.
Many people think of psychosis as a condition that results in severe delusions or hallucinations, but the more common form of it just makes it very hard to string cohesive thoughts together in order. That's even the main diagnostic criterion: how likely a subject's speech is to change subject mid-sentence. To your general "sense" of how smart someone is, psychosis can read very negatively, while not necessarily having any apparent impact on focused interpretation like IQ measures.
(Score: 1, Touché) by Anonymous Coward on Wednesday January 20 2016, @02:26AM
Well, it definitely does substantively affect likelihood of psychosis.
[Citation needed]
(Score: 2) by ikanreed on Wednesday January 20 2016, @05:17AM
Meta-analysis of existing research on the subject [procon.org]
(Score: 2) by mcgrew on Wednesday January 20 2016, @06:49PM
From your link:
The study did say there was an association between marijuana use and psychosis, but not that marijuana was the causative factor. I knew several crazy (as in later diagnosed as mentally ill) kids when I was a kid, and all of them wound up being stoners. I've known a lot of stoners, and the crazy ones were nuts before they took their first toke.
Carbon, The only element in the known universe to ever gain sentience
(Score: 2) by ikanreed on Wednesday January 20 2016, @07:04PM
That's a very generous reading of a summary that also includes language like this:
These longitudinal studies surveyed for self-reported cannabis use before psychosis onset and controlled for a variety of potential confounding factors (eg, other drug use and demographic, social, and psychological variables). Three meta-analyses of these and other studies concluded an increased risk of psychosis is associated with cannabis use, with an odds ratio of 1.4 to 2.9 (meaning the risk of developing psychosis with any history of cannabis use is up to 3-fold higher compared with those who did not use cannabis).
In addition, this association appears to be dose-related, with increasing amounts of cannabis use linked to greater risk—1 study found an odds ratio of 7 for psychosis among daily cannabis users.
As it goes on to note, that's not definitive proof of a causative function(which is hard to study for a controlled substance, which can't be administered in randomized trials), but if it doesn't make you go "That's a pretty substantial relationship", you're willfully glossing over the material to arrive at a predetermined answer.
(Score: 2) by mcgrew on Wednesday January 20 2016, @07:20PM
I'll admit I didn't read the whole study.
Carbon, The only element in the known universe to ever gain sentience
(Score: 0) by Anonymous Coward on Wednesday January 20 2016, @10:51PM
Same AC here. Now that wasn't so hard, was it?
(Score: 2) by ikanreed on Wednesday January 20 2016, @11:57PM
I never said it was hard, I just assumed the relationship was common knowledge. Dunning Kruger effect: you write your competencies and knowledge onto other people around you.
(Score: 0) by Anonymous Coward on Thursday January 21 2016, @04:52AM
I never said it was hard, I just assumed the relationship was common knowledge. Dunning Kruger effect: you write your competencies and knowledge onto other people around you.
Not a good assumption.
I mean, what with smoking up all the time, then freaking out and beating up homeless guys, busting plate glass windows or playing mailbox baseball, who can remember all the scholarly papers we read anyway?
(Score: 1) by Francis on Wednesday January 20 2016, @03:40AM
I'm not surprised that they found no correlation between IQ decline and pot use, the parts of the brain that pot affects aren't related to IQ.
Parts of the brain effected by pot are mostly in the PFC which means that working memory, short term memory and general executive function are likely to be affected by pot and that's where you're much more likely to see issues than with IQ.
The other really interesting question is really how much is too much. Clearly one joint isn't going to damage the brain to any appreciable degree, but spending most of your life toasted is highly likely to have negative consequences for the brain.