As marijuana use among teens has grown in the past decade, researchers have been trying to better understand the health risks of the drug. Now, a new longitudinal study finds that cannabis use among…
As marijuana use among teens has grown in the past decade, researchers have been trying to better understand the health risks of the drug. Now, a new longitudinal study finds that cannabis use among adolescents increases risks of being diagnosed with bipolar and psychotic disorders, as well as anxiety and depression, years later.
Related Story: NPR"This is very, very, very worrying," says psychiatrist Dr. Ryan Sultan at Columbia University, a cannabis researcher who wasn't involved in the new study published in the latest JAMA Health Forum.
Strong study design
Researchers analyzed health data on 460,000 teenagers in the Kaiser Permanente Health System in Northern California. The teens were followed until they were 25 years old. The data included annual screenings for substance use and any mental health diagnoses from the health records. Researchers excluded the adolescents who had symptoms of mental illnesses before using cannabis.
"We looked at kids using cannabis before they had any evidence of these psychiatric conditions and then followed them to understand if they were more likely or less likely to develop them," says Dr. Lynn Silver, a pediatrician and researcher at the Public Health Institute, and an author of the new study.
They found that the teens who reported using cannabis in the past year were at a higher risk of being diagnosed with several mental health conditions a few years later, compared to teens who didn't use cannabis.
Teens who reported using cannabis had twice the risk of developing two serious mental illnesses: bipolar, which manifests as alternating episodes of depression and mania, and psychotic disorders, such as schizophrenia which involve a break with reality.
Now, only a small fraction — nearly 4,000 — of all teens in the study were diagnosed with each of these two disorders. Both bipolar and psychotic disorders are among the most serious and disabling of mental illnesses.
"Those are the scarier conditions that we worry about," says Sultan.
Silver points out these illnesses are expensive to treat and come at a high cost to society. The U.S. cannabis market is an industry with a value in the tens-of-billions — but the societal cost of schizophrenia has been calculated to be $350 billion a year.
"And if we increase the number of people who develop that condition in a way that's preventable, that can wipe out the whole value of the cannabis market," Silver says.
Depression and anxiety, too
The new study also found that the risk for more common conditions like depression and anxiety was also higher among cannabis users.
"Depression alone went up by about a third," says Silver, "and anxiety went up by about a quarter."
But the link between cannabis use and depression and anxiety got weaker for teens who were older when they used cannabis. "Which really shows the sensitivity of the younger child's brain to the effects of cannabis," says Silver. "The brain is still developing. The effects of cannabis on the receptors in the brain seem to have a significant impact on their neurological development and the risk for these mental health disorders."
Silver hopes these findings will make teens more cautious about using the drug, which is not as safe as people perceive it to be.
"With legalization, we've had a tremendous wave of this perception of cannabis as a safe, natural product to treat your stress with," she says. "That is simply not true."
The new study is well designed and gets at "the chicken or the egg, order-of-operations question," says Sultan. There have been other past studies that have also found a link between cannabis use and mental health conditions, especially psychosis. But, those studies couldn't tell whether cannabis affected the likelihood of developing mental health symptoms or whether people with existing problems were more likely to use cannabis — perhaps to treat their symptoms.
But by excluding teens who were already showing mental health symptoms, the new study points to a potential causal link between cannabis use and later mental health diagnoses. Additional research is needed to understand the link fully.
"Playing with fire"
Sultan, the psychiatrist and researcher at Columbia University, says the study confirms what he's seeing in his clinic — more teens using cannabis who've developed new or worsening mental health symptoms.
"It is most common around anxiety and depression, but it's also showing up in more severe conditions like bipolar disorder and psychosis," he says.
Related Story: NPRHe notes that mental health disorders are complex in origin. A host of risk factors, like genetics, environment, lifestyle and life experiences all play a role. And some young people are more at risk than others.
"When someone has a psychotic episode in the context of cannabis or a manic episode in the context of cannabis, clinicians are going to say, 'Please do not do that again because you're playing with fire,'" he says.
Because the more they use the drug, he says the more likely that their symptoms will worsen over time, making recovery harder.
"What we're worried about [is if] you sort of get stuck in psychosis, it gets harder and harder to pull the person back," says Sultan. "Psychosis and severe mood disorders, particularly bipolar disorder are like seizures in your brain. They're sort of neurotoxic to your brain, and so it seems to be associated with a more rapid deterioration of the brain."
Transcript
SCOTT SIMON, HOST:
Marijuana use among teens has grown in the past decade, and researchers have been trying to better understand the health risks. Now a new study finds that cannabis use among teens increases risks of being diagnosed with bipolar and psychotic disorder years later. NPR's Rhitu Chatterjee has more.
RHITU CHATTERJEE, BYLINE: Researchers analyzed health data on nearly half a million teenagers in the Kaiser Permanente health system in Northern California. The data included annual screenings for substance use and any mental health diagnoses all the way until they were young adults. Pediatrician Dr. Lynn Silver at the Public Health Institute in California is one of the authors of the study.
LYNN SILVER: We looked at kids using cannabis before they had any evidence of these psychiatric conditions and then followed them to understand if they were more likely or less likely to develop them.
CHATTERJEE: They found that the teens who reported using cannabis in the past year were at a higher risk of being diagnosed with several mental health conditions a few years later, compared to teens who didn't use cannabis.
SILVER: What we found is extremely worrisome.
CHATTERJEE: The highest risk was for two disorders - bipolar, which manifests as alternating symptoms of depression and mania, and psychotic disorders.
SILVER: And psychotic disorders means ones where you hear or see things that aren't real. Typically, it can be anything from an episode to actual schizophrenia.
CHATTERJEE: Now, only a small percentage - about 1% of the teens - were diagnosed with these two disorders, but the risk of developing them doubled for teens who used cannabis versus those who didn't. Silver notes that both bipolar and psychotic disorders are among the most serious and disabling of mental illnesses. The risk for more common conditions, like depression and anxiety, was also higher among cannabis users. Silver hopes that the study published in JAMA Health Forum will make teens more cautious about using the drug, which is not as safe as they think it is.
SILVER: With legalization, we've had a tremendous wave of misperception of cannabis as a safe, natural product to treat your stress with.
CHATTERJEE: Psychiatrist Dr. Ryan Sultan at Columbia University also researches the impacts of cannabis use on teens but wasn't involved in the new study. He finds the results worrying, and it confirms what he's seeing in his clinic, more teens using cannabis who've developed new or worsening mental health symptoms.
RYAN SULTAN: It is most common around anxiety and depression, but it's also showing up in more severe conditions like bipolar disorder and psychosis.
CHATTERJEE: He notes that mental health disorders are complex in origin. A host of risk factors, like genetics, our environment, lifestyle and life experiences, all play a role, and some young people are more at risk than others.
SULTAN: Which is why when someone has a psychotic episode in the context of cannabis or a manic episode in the context of cannabis, you know, clinicians are going to say, please do not do that again because you're playing with fire.
CHATTERJEE: Because the more they use the drug he says, the more likely their symptoms will worsen over time, making recovery harder.
Rhitu Chatterjee, NPR News.
(SOUNDBITE OF YAMI/HIKARI'S "APRICITY")
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Comments
Marijuana legalization arguments were my first introduction to motivated reasoning. I was pretty inclined to agree that locking up non-violent drug offenders was a net-harm to society. But, the pro-legalization folks would argue patently crazy things: it cures cancer, the smoke isn't bad for you at all, there are no downsides! etc.
It seemed obvious to me that you could make a more realistic argument and just stick to an argument which states that due to drunk driving and domestic abuse, marijuana is less harmful overall than alcohol, but is treated as more dangerous. (and yes, the other side was a bit crazy too. "When you buy weed you're supporting the same terrorism that happened on 9/11")
Later research (such as this) has suggested a link between marijuana and psychosis, however the actual risk factors do seem difficult to nail down. (however, this is still a far cry from the claim that it's totally harmless)
What I ultimately learned is that in a pitched political battle, people actually damage their credibility because they're afraid to cede _any_ ground to the opposition, even when that means making unrealistic claims. A centrist (or just someone who is undecided) is not really taken in as much by these extremist argument, and to their eyes it damages the credibility of one or both sides.
Probably worth clarifying that when you say "But, the pro-legalization folks would..." you mean some stoners you met in college.
Because there are plenty of proponents who are not that... in fact 64% of Americans support making weed legal (2025), so it'd be really unfair to judge that movement based on those old experiences.
By cyanydeez 2026-02-2412:04 Yeah, it sounds like hs confabulating arguments about pain reduction in cancer patients with "cures cancer" from some nebulous source.
Cherry picking is pretty much the same as motivated reasoning when making arguments.
> But, the pro-legalization folks would argue patently crazy things: it cures cancer, the smoke isn't bad for you at all, there are no downsides! etc.
Who seriously claimed that it “cures cancer”? There have been some claims that it helps alleviate nausea associated with chemotherapy, which is quite reasonable and will likely be proved out by evidence over time.
Really … who genuinely claimed it “cures” cancer?
By brailsafe 2026-02-2322:07 I've heard people who clearly had psychological issues claim things like this, but nobody actually credible. Problem is that people fall down rabbit holes that perpetually reinforce their own spiral.
The combination of actual drugs and grief and real underlying mental disorders is a powerful and scary mix.
By gosub100 2026-02-2318:59 I took it as more of an exaggeration of "medical marijuana" - a phrase you could rarely get away from in the 2000s.
By troosevelt 2026-02-2318:54 There are things like "Rick Sampson oil". I'm sure there are believers.
all legalization frameworks in the US already limit legal age of purchasing possession and consumption to 21 and over, specifically as a form of seeding ground to the opposition, specifically for the previously only anecdotal link to psychosis and underdeveloped minds of minors
>But, the pro-legalization folks would argue patently crazy things: it cures cancer, the smoke isn't bad for you at all, there are no downsides! etc.
Using the most anecdotally crazy people you met to suggest that the pro-legalization movement is crazy, is frankly, crazy. I'm very involved in legalization and I don't know anyone that is for legalization that thinks any of those things, never even heard anyone say such garbage. I think you may be cherry-picking the crazy here.
I don't think you can frame some of these arguments as belonging to a fringe minority. I remember watching an episode of "Penn & Teller's Bullshit"[1](2004) where they featured several pro-legalization advocates. These folks said or implied similar things (it's not bad for you, it helps cancer patients). These were not marginal "crazy" voices.
[1] https://en.wikipedia.org/wiki/List_of_Penn_%26_Teller:_Bulls...
I know that I too say and heard those arguments a lot. You do yourside a disservice by claiming it doesn't exist
>Using the most anecdotally crazy people you met to suggest that the pro-legalization movement is crazy, is frankly, crazy.
This was over 20 years ago, long before "nut-picking" became impossible to avoid. This is what I was hearing from my peers on my college campus. They may have had had extreme views, but this was long before modern social media surfaced only the craziest people for any given position.
>Using the most anecdotally crazy people you met to suggest that the pro-legalization movement is crazy, is frankly, crazy.
Also, I disagree with this characterization. I am not crazy, it was unnecessarily rude to suggest otherwise. I'm repeating the arguments I heard from my actual peers. I'm not just finding extremists on the internet and painting the whole group by its worst members.
By buzzerbetrayed 2026-02-2318:441 reply To be fair, the example they gave from the other side is far more fringe
> When you buy weed you're supporting the same terrorism that happened on 9/11
I am firmly against marijuana legalization. This is partially because of this insanity of the pro-legalization arguments. When I would see friends/family that started smoking regularly become noticeably less intelligent while pro-legalization proponents would argue there are no negative side-effects, or people who were obviously compelled to smoke every day or as often as they could.... like some sort of addiction, while pro-legalization proponents argued it was totally not-addictive.
The anti-legalization side had a few odd arguments as well, and some old claims that were unfounded. So no hands were totally clean.
> I am firmly against marijuana legalization. This is partially because of this insanity of the pro-legalization arguments.
this is also just motivated reasoning
The insanity of the fringe pro-legalization arguments has no bearing on whether legalization is a good idea or not.
> When I would see friends/family that started smoking regularly become noticeably less intelligent while pro-legalization proponents would argue there are no negative side-effects
This is also just ripe for cognitive bias which is why we should use science to understand these types of claims.
Did the people you notice becoming less intelligent ever recover? I'm genuinely interested. My biggest regret in life is early years drug use, smoked my first joint at 13. Mdma 18. Cocaine late tewnties. I personally think marijuana might be worse than mdma but not by much. And cocaine is really bad for cardio vascular system, probably physically worst of all of them that I tried.
I think both mdma and marijuana cause anxiety and they mess with short term memory.
There doesn't seem to be a good answer to protecting kids from drugs. Heavily regulated legalisation might help or it might normalise drug use.
As an aside I personally think alcohol in very moderate use isn't really as harmful as other drugs. And is probably a net benefit for many. Even moderate use of illegal drugs seems to have bad affects on people.
Edit: added my thoughts on alcohol and something on cocaine use.
By dec0dedab0de 2026-02-2319:051 reply I am firmly in favor of legalizing all drugs, except maybe antibiotics where overuse is causing harm for everyone.
The thing is, I 100% agree with your reasons for why it should be outlawed. I just think those are reasons to discourage using it, especially chronically.
However, I wholeheartedly believe the government should not have any say in how anyone lives their life, and treats their own body.
By something765478 2026-02-2318:552 reply I'm curious, do you also think alcohol and tobacco should be banned? I definitely believe that marijuana use can lead to negative consequences, but I still think it is less dangerous than either of those 2 substances.
By aaomidi 2026-02-2318:39 I never understand this line of thinking.
So the easiest way for an opposition to a good idea to get their way, is to go argue insane things on the opposite side?
Imagine if the oil industry starts paying people to go throw soup on paintings just to make the pro “let’s prevent climate change” people look stupid.
Oh. Wait.
>I am firmly against marijuana legalization.
Is there an argument or data that could be presented that _would_ change your mind?
But why is alcohol legal then? It has worse side effects and more collateral damage.
By whattheheckheck 2026-02-2321:181 reply Are you also firmly for alcohol abolition? What about gambling?
By throwaway27448 2026-02-2319:40 > What I ultimately learned is that in a pitched political battle, people actually damage their credibility because they're afraid to cede _any_ ground to the opposition
This could be a person making a bad argument, or it could be that the individual is the opposition trying to poison the well. Cf COINTELPRO. Largely any movement has people with insane takes, and it's impossible to tell the difference between good and bad faith actors.
That, and sometimes people just aren't trying to be persuasive at all. It's extremely rare to actually see someone persuaded about anything political without enormous amount of effort, or more realistically a change in material interests.
By Teever 2026-02-2317:55 Yes, what you observed is people making unrealistic and disingenuous responses in reply to equally unrealistic and disingenuous reefer madness type propaganda.
What happened is that the people making these disengenuous comments in bad faith did not realize that so many others would watch them and without understanding hte context woudl pick up those same disingenuous arguments and take them as truth.
This is all the long term consequences of allowing Reefer Madness tier propaganda be published and not repudiated immediately.
By btreecat 2026-02-2320:51 TBF, if your paraphrasing others as "curing cancer" but what they claimed is "treats cancer" then the issue may be comprehension or activite listening.
Something to consider.
By tuesdaynight 2026-02-2412:49 Honestly, I consider myself a "centrist", but I'm always frustrated how that means "do not take sides" for some people (not saying that is your case). In this case, not taking sides means that weed is illegal and people go to jail if they dare to use it. In the country that I was born, it's still illegal. I know stoners there and it's crazy how they could spent years in prison if someone told the police that they cultivate cannabis in their house. They do not sell and do not share with anyone, but they are one call away to be jailed.
I get it when people talk about society effects, but how are my friends dangerous while buying and drinking a lot of alcohol is totally okay? Taking no sides in this case is just maintaining status quo, which is not a "centrist position" when one side can be jailed for using weed.
By cwmoore 2026-02-2520:46 Indeed. What an asinine result. Let’s see the same study with alcohol, tobacco, and prescription medications before putting out words that have meanings.
"But by excluding teens who were already showing mental health symptoms, the new study points to a potential causal link between cannabis use and later mental health diagnoses. Additional research is needed to understand the link fully."
Hm, but this does not exclude the possibility that the being prone to mental illness comes with a little bit higher tendency to consume cannabis...
Similarly, cigarettes also have a very strong correlation with schizophrenia. Completely non-causal, but it's hard to find a non-hospitalized schizophrenic who does not smoke.
When I read this article the other day I had the exact same thought. Is this simply correlation, or is it causation? Is teenage usage an indicator of a possible underlying condition that hasn’t fully manifest? Is it an early form of self medication?
By M95D 2026-02-2320:51 And the only way to tell is to randomly split teenagers into two groups: cannabis vs. control. But no parent would give consent, so we will never know.
By joquarky 2026-02-2320:35 Let's not forget that many mental health "disorders" are just elaborate labels for having difficulty conforming to arbitrary cultural expectations.
By tsoukase 2026-02-2322:54 Its a correlation result and not causation. The author makes a mistake, off course. Mental diseases have effects since deep in a young age and push for increased marijuana use, but also nicotine, benzos and, may be, obesity, aggressiveness, school dropout, parent's divorce, low vitD and a long list of possible factors. All these will be correlations.
I used to read forums for schizophrenics (self disorders fascinate me, look the term up if you want to understand schizophrenia), and it was the consensus there that out of all the recreational drugs cannabis caused the greatest deterioration in one's mental state. Those are generally fairly sick people, but I don't think one can just ignore this signal. I personally went catatonic once after consumption, and I'm not schizophrenic at all. And that was in Amsterdam, so it wasn't some trash spiced up by a 17-years old dealer with whatever he found in his grandma's medical cabinet.
By orionsbelt 2026-02-2318:112 reply I don’t know what things are like in Amsterdam, but weed being “high quality” is not a good thing. The potency has skyrocketed over the past few decades. It’s like saying you went to Amsterdam to drink alcohol for the first time and had a bottle of tequila and passed out and puked; the fact that it was high quality tequila does not mean it’s better than a low quality glass of wine or beer. The issue is the doses are way too high.
By ProjectArcturis 2026-02-2321:37 Continuing the analogy, it does mean that they can blame the alcohol and not, say, rohypnol for their outcomes.
By galleywest200 2026-02-2317:40 > it was the consensus there that out of all the recreational drugs cannabis caused the greatest deterioration in one's mental state
Methamphetamine and PCP might take issue with this statement.
By swed420 2026-02-2321:06 But imagine the kind of self-selection you'd find on such a forum. Furthermore, it's been long known that cannabis use can trigger schizophrenia in those who were already genetically predisposed to such. Your observation and the OP are not news worthy, imo. Bad outcomes have also been observed when combined with immature brains.
But for healthy adults, countless have used cannabis for generations without experiencing harmful reactions.
This one's my favorite: https://thereitis.org/mr-x-by-carl-sagan/
By sfjailbird 2026-02-2318:091 reply Weed can make you paranoid, every smoker knows this. It is patently obvious that it could trigger something worse, too, if you are already sensitive.
I think only young people in their weed honeymoon phase get defensive about this.
By DANmode 2026-02-241:55 Acute toxicity from a variety of other intoxicants can, as well.
THC is a toxin!
By FeloniousHam 2026-02-2419:52 I'd been a casual user for a while (very sporadically in illegal days, regularly once legalized). I happened to going through a fairly traumatic breakup, and felt that if it didn't actually help me get to sleep, it at least made the insomnia tolerable.
My life settled down, but I continued to smoke a tiny bit. One puff really, before bed pretty much every night. When things were crazy and awful, I didn't care about feeling mossy the next day, but as normal life resumed, it definitely started to affect my attention.
Then, the "intrusive thoughts" started. It's like having an edge lord in your head. Whatever you think about, the idea gets lensed(?) from the worst/most extreme possible viewpoint/conclusion. It's hard to describe, but it was very distracting, and often just depressing. And of course, waking up at 3am every night, this is what I had to look forward to. And sometimes, I'd take a little toke in the hopes I'd get back to sleep.
Here's the punchline: I quit smoking and it went away in two days and hasn't returned.
By selectodude 2026-02-2318:062 reply Problem with recreational marijuana is that it’s so insanely strong. It would be like giving a child 190 proof azeotropic grain alcohol and being shocked that they immediately vomit. I can’t smoke pot - it’s just too strong.
I’ll admit to feeling a bit dumber and foggier after a few weeks of ingesting cannabis nightly though. That’s a real thing.
