"The data you want, is to take a relatively normal population of teens from families of average stability, dietary habit, who don't abuse alcohol, cigarettes and hard drugs.  This is where the prohibitionists have a field day in their negative studies, and impose their findings on a public that has, well a low IQ."


The idea that cannabis leads to cognitive impairment is a hot topic.  Certainly, if you've a stoner or been one, you notice that their IQ is altered, and certainly goes down in some areas, in some instances.  Then you have your stereotypical stoner, lazy, dumb and foolish.  The off hand conclusion, made by people of low IQ themselves is that marijuana makes you lazy and dumb.


However, this idea that marijuana lowers IQ is not born out in many examples, nor even scientific and statistical studies.  Further compounding the data is that people that suffer from cognitive dysfunction that find improvement with cannabis treatment do lower the average IQ of the user group.  Again, the low IQ researcher ignores this fact, which is akin to saying that a patient taking Drug A to treat cancer means Drug A causes cancer.


Cannabis is the only medicine that really works.


What is really brutal about IQ studies is to assume it's one thing, or a couple of things.  What does IQ include?  emotional intelligence? artistic ability? musical ability, or just playing with numbers and words with pattern recognition.   Often is the case, people have this crazy idea, and say, he has a really high IQ, but no street smarts or he doesn't understand women, etc.  

Intelligence is many faceted, the ability to figure a chess game and do equations is only a small part of the intellectual ability of humans.   




"Interestingly, in states that have legalized the herb, cannabis use among teens has gone down.  In Colorado, teen use in the past month declined from 24% in 2009 to 21% in 2015. Opiate and overdose deaths were down. Rather than being a gateway drug, the statistics show exactly the opposite effect."


After all is said an done, is it not easy to see if a drug is causing problems?  Yes it is. There is the productivity meter.  There is the social interaction meter.  There is the creativity meter. Two factors that cause people to fail in seeing the light is a bias against weed, and denial, the warped mentality of the cannabis user.  Thus, some long time weed users actually suffer from a real decline in emotional IQ, which comes with other subtle losses in cognitive function.  Fortunately, the consequences of weed abuse pale in comparison to other substances and long lasting effects don't seem to be an issue.


Let's move onto a large scientific study on the topic, where the conclusion is that marijuana use overall, even heavier use, does not affect IQ in any major way.


"The predictions of fire and brimstone have failed to materialize. Most Coloradans, including the governor, recognize that the law is working."  - Colorado isn't seeing IQ problems




It is a classic “chicken or egg” problem.  Extensive past media attention suggests the detrimental effects of cannabis on brain function and mental health; smoking a spliff is akin to repeatedly bashing yourself over the head with a giant bong. However, scientific studies to date tend to be cross-sectional ( measurements are taken fraction of a person’s life), it cannot be determined that cannabis users would have performed any differently before they started using cannabis.

Cannabis use does not occur in a vacuum-  teenagers who start using cannabis from a young age differ from abstainers,or smoke for the first time when they are older.


Some kids that smoke cannabis at a young age have less stable backgrounds and more issues to deal with, like a broken family, domestic violence and an outrageous community full of gangs. Who wouldn't want to take something in these kinds of shithole environments?  Hard drugs will kill you, but weed, would this be the smarter choice?    Certainly, no growing person should play around with any drug what so ever, in their formative years, however, after growth is complete, so many natural substances taken in moderation have beneficial effects.  




"It is obvious that some people build up a tolerance over time, especially seen in using high THC strains for a long time.  Symptoms include anxiety, paranoia and a sense of detachment.  Unlike alcoholism, negative effects are inclined to cause users to stop, while some alcohol users continue unabated." - Dr. J

Researchers from University College London and University of Bristol conducted a study, using data on 2235 teenagers.   They looked at the relationship between how many times someone reported cannabis use at age 15 compared with an IQ test.


"It's back to nature.  Marijuana users should smoke weed that contains an assortment of cannabinoids, along with THC, there should be a  few percent of CBD, and values of CBC, and CBN.  Adding a bit of essential cannabis oil to bud (terpenes) is a good idea, because the terpenes highly medicinal and are volatile, lost over time." - Johnny Rodriguez

Teen cannabis users performed worse on their teenage IQ tests, after accounting for their ‘baseline’ IQ at 8 years old. Sporadic cannabis users scored roughly 2 IQ points lower.  But then they looked deeper.  Those same teens were prone to break the laws of the land and were far more likely to smoke cigarettes, take nasty drugs and engage in not so intelligent behavior.  The data you want is to take a relatively normal population of teens from families of average stability, dietary habit, who don't abuse alcohol, cigarettes and hard drugs.  This is where the prohibitionists have a field day in their negative studies, and impose their findings on a public that has, well a low IQ.


"Most strikingly we saw that cannabis users were also much more likely to be tobacco cigarette smokers- 84% of those in our heaviest cannabis use group (who reported having used cannabis at least 50 times by age 15) had smoked cigarettes more than 20 times in their life, compared to just 5% of those who had never used cannabis."


The heaviest using teenagers used cannabis around  two years, and had used cannabis at least 50 times each (although 57% of this group reported having used cannabis at least 100 times).


When statistically adjusted for substance use, behavioural problems and mental health symptoms, cannabis use could no longer be correlated with lower IQ scores, there was no difference to those who had never tried cannabis. An analysis of school GCSE grades verified this non-association with cannabis use and grades.


"While this may sound like great news for those 15% of 15-24 year old Europeans who have used cannabis in the past year, the take home message is sadly not so clear cut. This is just one study from one cohort in one area of England, and as authors of the paper, we are the first to acknowledge the limitations of this work, including the young age of the participants when we measured IQ, and the relatively moderate levels of cannabis use."


In a 2012 study those who showed the most dramatic IQ decline had been cannabis abusers from adolescence until their late 30’s; had been diagnosed with cannabis addiction.  Focusing on people with addiction disorders, as was done in this study, is no way to find out what happens to normal individuals.


"CBD in the cannabis friendly press is seen as a saintly compound, it doesn't get you high, is highly medicinal, and balances THC.  While all of this is true, in many cases, some individuals don't respond well to higher amounts of CBD.  Basically, you have to try different strains, and look at the cannabis profile and terpenes to figure out what's best for you."


MMJDOCTORONLINE NOTES: If you suffer from chronic stress, pain, inflammation or other conditions and symptoms, you may qualify for a medical doctor's recommendation.  In California, the process of getting California Cannabis ID can be completed online.  Our process is free to apply and patients only pay once they have been approved.  The cost of a 420 evaluation is probably less than the tax you'll pay as a recreational user for one ounce.  MMJDOCTORONLINE documents and cards are used at licensed dispensaries, delivery services, cannabis clubs, and other points of access in California.









yesThe authors found decreases in ability among marijuana users compared to non-users in two modules – Vocabulary and Information – associated with “crystallized intelligence”, or the ability to use learned knowledge.

yesyesThe authors noted, however, that in one of the two studies, 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.


yesInteresting. so people with lower IQ scores are more "inclined" (probably not the best word) to use marijuana

yesSmoking pot doesn't make you stupid or lazy but a lot of stupid lazy people smoke pot because ... (drumroll) doesn't kill you (and thereby thresh for intelligence).

yesThere probably aren't any significant universal attributes of marijuana users other than their use of marijuana.

yesI think we should start there because it tosses out the stereotypes. But I would really like to know why after several years of sobriety my brain still loves weed while many people I know trying it again aren't that interested. There is something about my brain/body/perspective that makes me want all the marijuanas.

yesI used to be all about it from 2008-2011. Loved being high all the time. Enjoyed it, did well in school, had social life, worked out. Around 2012 I just started to hate being high, started getting paranoid and anxious and shit. I rarely smoke now, and when I do, like 75% of the time I get anxious and regret it.

yesHow old were you when it changed?

yesNot OP but my experience is exactly the same as his and the change happened for me at age 22.

yesDo you think there's something particular happening at that age that makes this, because I am random sample number three in this thread confirming the same thing - just turned 23, fed up with the anxieties and paranoias for several months now and gradually stopping.

yesyesyesBased on the other responses it seems like a lot started fairly young, probably in high school. I was a goody two-shoes who never did any drugs or alcohol. I turned 21 and didn't drink, first time drunk was 24, turned down vaginal sex with a couple of partners and lost my virginity with my now wife at 25, for high by smoking weed at 26 for the first time and quickly switched to vaporizers and I edibles only. From 27 until 30 were my heavy usage years meaning I would get high most days once or twice, usually just helping my much heavier user of a roommate finish a bag (on out vaporizer). The roommate moved out and I switched to a portable vape and used it about 3 times a week, moved into a new place with another regular used and it picked up again, usually partaking in bags he wanted to make. That roommate moved away about 2 years ago now and I rarely get high any more. I do get a steady supply of already vaped weed (it's toasted and brown as its been though, essentially and oven), we call it ABV (already been vaped) and it's amazing stuff. Shortly after I started vaping I learned that the leftovers once you were done still contained a little THC and a lot of cannabidiol CBD. I looked extraction methods and settled on a coconut oil extraction which I place into gel caps. I get a steady supply of ABV from my ex roommates, I turn to into capsules and keep 60%. One capsule relaxes my muscles and helps with general pain, achy back, and general anxiety, I get a little bit of a warm pleasant body high. Two capsules and I'm head high as well, sex becomes amazing and it helps with erection strength and makes orgasms out of this world. Three capsules are often too much unless I've been regularly vaping, sometimes good for parties, especially if we're playing Cards Against Humanity.

yesIf you check my submitted posts you can find my oil recipe or head over to /r/ABV, it should still be semi close to the top, maybe a couple pages in.

yesTL;DR - it seems most people that quit in their early 20's started quite young. A lot of people seem to cut way down or stop after a few years.

yes22 here as well. Maybe its the age we start getting real responsibility? Or something biological. I still love and use it, but couldn't function doing it every day like i used to.

yesSame thing happened to me, about the same time frames too. Eventually I just stopped trying to smoke altogether.

yesWow - I'm exactly the same. To be honest I wish I could still smoke because I had some great times, but 90% of the time now it gives me a panic attack.  

I'm right there with you.

yesThat directly contradicts the result of the study, as quoted just three links up in the reply chain. Unless you're being literal with your use of "universal," which is inherently meaningless in a statistical/probabilistic study.

Maybe he just smokes too much and therefore can't apply the stuff he just learned.

Where C is a common cause, S is heavy smoking pot and L is Low IQ. It stands that having a lower IQ doesn't make pot more or less attractive.

yesWhat is the common cause? There's a bunch of things it could be. The biggest candidate is social support. People who become socially isolated would find drugs more attractive. People who suffer cognitive disability and have trouble learning (aka. "stupid") find drugs more attractive. People who have emotional issues (depression, etc.) that cause them to be unmotivated (aka. "lazy") find drugs more attractive. Lack of social support is correlated with drug use and low IQ. There's a lot of data to argue that drugs aren't the cause, but a symptom, but I have yet to see good conclusive research that proves clear causality (but again there's a lot out there pointing towards that).

yesThey 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.

yesThere is a lot of hand-wringing going on about the legalization of a substance that is quite probably safer than alcohol, as far as cognitive ability is concerned.

About the legalization of a substance that is quite probably safer than alcohol

yesBeing 'safer than alcohol' is hardly a glowing recommendation, considering the damage alcohol can do to an individual, and does do to society in general.

How do you quantify a substance being illegal or not if not based on how dangerous it is? The entire basis of it being illegal is it is a dangerous drug, similar to other drugs in it's schedule such as Heroin and bath salts.

yesThere doesn't need to be a "glowing recommendation", the fact that many states have medicinal laws for marijuana completely contradicts the federal drug scheduling system. It's ridiculous that you can "legally" do something in one state, but it's federally illegal in every other state that hasn't passed laws contradicting the federal law.

yesyesFYI, heroin is actually a schedule below marijuana, along with cocaine. Marijuana is schedule 1 (along with LSD and psilocybin mushrooms, both of which have also killed a total of zero people) in regards to having "absolutely no medical value". Heroin and coke are schedule 2 because they have "some medical value," medical use being the current form of determining a drug's legal status.

yesyesConsidering we've had scientific studies stating MDMA, LSD, Psilocybe cubensis and cannabis possessing some medical value (the former three for therapeutic methods, the latter for numerous ailments), the current scale is a load of BS... although expecting a nation brainwashed by DARE and propaganda to take a sensible stance on drug use is a little much, I guess.

yesYou missed /u/Super Nazz's point. He's not saying throw out the study. He's saying let's stop comparing alcohol and marijuana because they're not even in the same playing field. My own 2 cents: let's compare marijuana to coffee and tea.

yesyesyesDon't think comparing a psychoactive drug to stimulants is good either.

yesI think one reason for comparing it to alcohol is that alcohol is over-glorified in the US while marijuana is still unfairly compared to other schedule one drugs. There are many that make drinking alcohol a hobby but would become hysterical if you mentioned smoking weed.

yesThat being said I can see how changing the discussion to something more mundane provides an opportunity to educate people that marijuana is not a life-ending disaster and could help open minds to the medicinal benefits.

Which makes little sense.

yesThe effects of coffee on your system aren't anywhere near as strong or as impairing on your system as marijuana, in the doses we use of each. Trying to argue over how much something harms you is a dumb comparison for most of society's concerns. How it affects you is far more more pertinent, and that's why it gets compared to alcohol and narcotics.

You should watch 10 things you don't know about - Season 3 Episode 7 Marijuana. It will open your eyes to how it got to become a schedule one drug.

That's how the US of A was designed to work. "Alright, so the Fed does X, and States are in charge of Y. "But what about Z?" "Whatever, State's rights and shit."

yesThe problem is, the Fed has made X illegal. The states are actively ignoring the Fed's opinions on X, and have legalized it in varying degrees. The fed sent in people to penalize people for listening to them instead of the State, but have given up for the time being. This is not how it's designed to work.

yesWell the mainstream opinion was that prohibition was horrible and a failure. So it might not be a glowing recommendation, but common sense dictates that it really should be legal, for the same reasons as alcohol is.

yesThere are bad things that happen, yes, but it seems fairly ridiculous to downplay the importance of alcoholic beverages in human culture and the benefits that they have brought forth.

And DEFINITELY safer from a general health standpoint.

My point was more "The use of that quote without this one is disingenuous"; I won't speak to my interpretation.

I agree it was disingenuous, I was just providing my own interpretation.

What you succeeded in doing was partially manipulating people by taking something out of context

yesThe study also found no relationship between heavier or more frequent marijuana use and the magnitude of IQ decline. The authors note that their study, unlike some previous research, did not ask participants about their current use, but only the greatest use since the initial testing.

yesThe participants may have been smoking every day for years.

yesSo while the results cannot rule out a causal relationship between near-term use and cognitive ability, the findings do agree with previous studies finding no relationship between prior heavy marijuana use and long-term cognitive impairment.

C'mon, the decrease in use of vocabulary and information is why people get stoned. It's funny and/or interesting.

yesyesI don't personally think it's decrease in use of vocabulary, but rather the brain making new associations between concepts, and getting an epiphanies of those associations. Like "socks are mittens for feet", associating socks with the category "warming sack like clothes you put at the end of your limbs" where mittens also go. Or "beef jerky is like meat raisin", associating beef jerky with the category "foodstuffs made by drying another foodstuffs" which beef jerky and raisins both are, or "the music is too loud, could you turn off the lights" associating volume to the category "sensation which can be decreased via electronics" where lights also belong. These associations get mixed casually causing funny and interesting epiphanies.

yesI also think it eases you up, makes you more likely to say the silly things that pop in your head. No filter. It can allow you to follow thoughts you would normally ignore. And creative, intelligent conversation thrives on that.

yesyesFinally, 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. The authors also focused on twins where one sibling used marijuana and the other didn’t, assuming similar genetic, socioeconomic and environmental factors for each member of the pair. These analyses, performed on more than 200 twin pairs, found no significant difference between users and non-users.

yesIf you read the rest of that paragraph, it explains that the marijuana users typically had lower scores in those areas before using marijuana. It suggests that a person that has lower scores in those areas is more likely to use marijuana, and even states "Where, marijuana use does not precede cognitive decline"

yesBut doesn't "decline" mean it is lower at moment b than at moment a? I see everyone explaining that cognitive abilities were already low to begin with and therefore there is no decline. Maybe it's because English isn't my first language but I don't get it. Can someone explain this to me?

yesSeems pretty convenient to just write off any findings contrary to your thesis as being caused by outside influence. Especially considering they were using twins to eliminate these haha. It's honestly a horrible study that doesn't prove anything either way but it has a catchy title so the media will over report it.

yesCherry picking sentences from an article about scientific study like this with no context should be against the rules. It's akin to a click bait headline that doesn't accurately represent the content of the article. It's very misleading without context.

yesPicking sentences from an article like this should be the rules. It's akin to a headline that accurately represent the content of the article. - /u/eel_heron

This makes sense. Sometimes I have a good idea of what I'm on about but for the life of me cannot convey what I need to. It can be hard to put my thoughts into words is another way to put it.

This is me when I'm not on anything.

Some people have a way with words, and others...uh, well, not have way, I guess.

Yuh know Julian is just like book smart and good with words and stuff and I like have different kinds of smarts.

So basically they still have the ability to learn hence Intelligence Quotient does not change, but they have lessened ability to actually use the new information? If that is the case it doesn't seem like a trade off for the better.

yesyesDoes IQ have any correlation to achievement? Can two people have the same IQ and one be less motivated and perform to a lower level? There has to be a reason why habitual users that begin at a young age generally have lower levels of achievement in the socially accepted meaning of the word (advancement in personal wealth and career, clean legal record, home ownership).

Does IQ have any correlation to achievement?


What does IQ include?  emotional intelligence? artistic ability? musical ability, or just playing with numbers and words with pattern recognition.

Yes, in fact some studies have found correlations between IQ and academic achievement of up to 0.80 (very strong).

achievement in the socially accepted meaning of the word (advancement in personal wealth and career, clean legal record, home ownership).

With grade inflation and all that, I don't know how relevant academic achievement still is.

yesYes, there are correlations between IQ and measures of achievement. The Bell Curve makes a very good case. It is also highly controversial because of findings related to race, but I haven't been able to find any criticisms of substance. I'd be very interested if anyone could provide some.

Can two people have the same IQ and one be less motivated and perform to a lower level?

yesYes. Statistically speaking, people with higher IQs tend to achieve more, but it isn't a perfect 1:1 correlation. In other words, there are plenty of people with higher IQs that achieve less.

There has to be a reason why habitual users that begin at a young age generally have lower levels of achievement

yesyesIs it so difficult to believe that someone with low motivation will gravitate to using marijuana (or drugs in general) recreationally? This doesn't that marijuana are responsible for a decrease in IQ, motivation, or achievement. The findings here seem to indicate just the opposite; namely, that marijuana may have a stronger attraction to people with lower drive or IQ.

yesThe Bell Curve makes a very good case. It is also highly controversial because of findings related to race, but I haven't been able to find any criticisms of substance. I'd be very interested if anyone could provide some.

yesyesSure, the racial differences have been consistently shown to be better explained by environmental factors (e.g, al literacy, education, nutrition etc.). There is a huge amount of research on that. Another way to show it is that the Flynn Effect is actually slowing down in many educated/wealthy parts of the world but not in poorer areas. Someone more in the area may be able to provide links but my understanding is that it's completely accepted in the psych community that there's no meaningful IQ difference between races that is due to any genetic component.

Could you provide more information on the Flynn Effect?

In a sentence, the Flynn Effect is the observation that IQ test scores have to be constantly revised downward because people keep scoring higher and higher, especially in developed and developing areas.

Noting that IQ is a normalized bell curve and not an absolute metric.

From memory, the wiki article on this is fairly decent. Have a read and let me know if you get stuck on anything -

yesThe scores for intelligence tests have to be revised because the mean result tends to be above 100. However, the results are normed in a way that the mean of a population should be 100. That is why they are revised and that is the Flynn effect. Therefore, the effect regards only the whole population. If a subpopulation gets an increase in scores over time, that is not the Flynn effect itself.

yesYep I'm usually a science-based person but for the case of marijuana I think people should try to take anecdotal evidence into account. It does have bad side effects for frequent use and those should be weighed against the positive effects.

I feel the good outweighs the bad significantly.

I am happy to see a lack of dogma in these threads though. People seem to be approaching the issue with a fair bit of intellectual honesty and an open mind.


Credits in part to Reddit.




Children of the Children of the 90s (COCO 90s)

Children of the 90s is a group of around 14,500 children born in the Avon area in 1991 and 1992. Scientists have been studying them ever since and are constantly making discoveries that make a difference to lives around the world.


No, marijuana use doesn't lower your IQ - The Washington Post

Yet another study finds no relationship between teen marijuana use and IQ



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