What I Wish I'd Known About THC and the Teenage Brain
I was driving into New York City to meet with a therapeutic team when I put on a podcast a colleague had mentioned, Schizophrenia: Three Moms in the Trenches. The hosts were interviewing Laura Stack, who founded the nonprofit Johnny's Ambassadors after her nineteen-year-old son, Johnny, died by suicide in 2019. He had become psychotic after dabbing high-potency THC. In the weeks before he died, he believed the mob was after him.
By the time I reached the city there were four mothers in my head, each of whom had raised a son through a serious neuropsychiatric disorder. Some of those disorders were genetic. Some were set in motion by cannabis. I felt the particular grief that comes from recognizing your own family in someone else's. And I felt something deep, we dodged a bullet.
My son used high-potency THC for years, in every form it comes in. He started around fifteen. Then the pandemic arrived, school moved to a screen, and the use climbed. He became a legit aficionado. He could walk you through the strains, the potency, the differences most people wouldn’t care to know. For a long stretch I told myself what a lot of loving, educated parents tell themselves. It's just weed. It could be so much worse. At least he isn't drinking. If it takes the edge off his anxiety, maybe it beats an SSRI.
I did not know then what I know now. By her own account, neither did Laura Stack.
This piece is the result of going back and learning what I should have learned the first time. It is not a lecture, and it is not panic. It is the information I wish someone had put in front of me when my son was fifteen and I was telling myself it was fine.
Johnny’s Ambassadors is a great resource for learning about the dangers of THC to the adolescent and young adult brain.
THC can be 70-90% more potent than the marijuana of the past
The first thing I had wrong was the substance itself. In the mid-1990s, the average cannabis flower contained roughly 4% THC. Today the flower sold in a dispensary commonly runs north of 20%, and the concentrates my son preferred (dabs, wax, shatter, vape oil) routinely reach 70% to 90% or higher. Dabbing strips the THC out of the plant into a concentrated form that is vaporized and inhaled, often with little smell, which is part of why so many parents never notice.
When people my age picture marijuana, we picture something that no longer exists in most legal markets. The potency has changed by an order of magnitude, and the research is only now catching up to what that means for young brains. (For a fuller rundown of the risks and the myths I used to believe, see my earlier post, Marijuana Use: What Parents Should Know.)
Why the teenage brain is uniquely vulnerable
The human brain is not finished at eighteen. The prefrontal cortex, which governs judgment, impulse control, planning, and the ability to foresee consequences, keeps maturing into the mid-to-late twenties. Adolescence is a period of heavy construction: the brain prunes away the connections it doesn't use and strengthens the ones it does, refining itself into its adult form.
That pruning is guided in part by the endocannabinoid system, a signaling network the brain uses to regulate mood, memory, and the timing of its own development. THC works by binding to one of that system's receptors (CB1), which is densely concentrated in the prefrontal cortex, hippocampus, and amygdala, and which is especially active during the teenage years. When THC floods that system from the outside, the brain's own signaling quiets down. Researchers describe THC as disrupting the timing and selectivity of pruning during the exact window when that process is most consequential (American Heart Association, 2022). Brain-imaging studies have linked adolescent cannabis use to faster thinning of the prefrontal cortex, and longitudinal work has associated heavy, persistent use that begins in adolescence with lasting deficits in attention, memory, and processing speed, and in some studies with a measurable drop in IQ (Volkow et al., 2014).
None of this proves that cannabis ruins every teenage brain that touches it. It does explain why age is not a side detail. The same exposure that an adult brain may largely absorb can land very differently on a brain that is still being built.
What the newest research says about THC Induced psychosis
The link between cannabis and serious mental illness is no longer a fringe concern. The most recent studies are the most sobering.
In February 2026, researchers at Kaiser Permanente Northern California published findings in JAMA Health Forum tracking 463,396 adolescents from ages 13 to 17 into young adulthood (Young-Wolff et al., 2026). Teens who reported using cannabis in the past year were about twice as likely to later be diagnosed with a psychotic disorder, and about twice as likely to be diagnosed with bipolar disorder. The association held even after the researchers accounted for prior mental health history and other substance use. Two findings stand out for parents. This was any use, not heavy use. And the cannabis use came first, on average a year or two before the diagnosis, which strengthens the case that this is more than coincidence (though the authors are careful to note that a study like this cannot prove cause, and that some teens may use cannabis to quiet symptoms that are already emerging).
Older research fills in the dose-response picture. A large European study led by Marta Di Forti found that people who used cannabis daily were roughly three times more likely to have a first episode of psychosis than those who never used, and that daily use of high-potency cannabis (over 10% THC) raised the risk to nearly five times (Di Forti et al., 2019). In some cities where strong cannabis is the norm, the researchers estimated that a substantial share of all new psychosis cases were tied to it.
And in Canada, a 2025 study in JAMA Network Open tracked the entire population of Ontario and found that the share of new schizophrenia diagnoses associated with cannabis use disorder almost tripled over seventeen years, a period in which cannabis was liberalized and potency climbed (Myran et al., 2025). Among young men in particular, the connection was strongest.
The takeaway is not that every teenager who tries cannabis will become psychotic. Most will not. The takeaway is that age matters, potency matters, frequency matters, and the risk for the most serious conditions does not always fade as these kids move into their twenties. The vulnerability appears strongest during adolescence itself, when the brain is least equipped to absorb the exposure (McDonald et al., 2024).
Why It’s Hard to quit Using THC
There is one more piece of the science I wish I had understood, because it quietly undermined the plan I never really admitted I had, which was that he would grow out of it before it did any harm.
THC is lipophilic, which means it is fat-soluble. Unlike alcohol, which clears the body in hours, THC and its metabolites are absorbed into fat tissue and released back into the bloodstream slowly, over days and weeks. In an occasional user, it clears in a few days. In a chronic, heavy user, the elimination half-life stretches to one to two weeks, the metabolites can be detectable in urine for a month or longer, and the body essentially holds a reservoir of the drug that it lets go of gradually (National Institute on Drug Abuse, 2024). The heavier and more potent the use, the deeper that reservoir runs.
What that meant in practice, for a teenager using high-potency concentrates almost daily, was that his brain was rarely without it. The exposure was not a Friday-night event that resolved by Monday. It was closer to constant. For a brain in the middle of its most important developmental years, that is exactly the wrong kind of steady.
There is also the matter of addiction. Cannabis use disorder is real and recognized, and the risk climbs for anyone who starts young. Research suggests that up to roughly three in ten users develop some degree of dependence, and the odds are higher for those who begin in adolescence (National Institute on Drug Abuse, 2024). Cannabis withdrawal is now its own diagnosis in the DSM-5, and a 2020 meta-analysis found that close to half of regular users develop withdrawal symptoms when they try to stop (Bahji et al., 2020). Those symptoms are not gentle. The most common ones are anxiety, irritability, trouble sleeping, restlessness, and low mood, often alongside physical symptoms like headaches and stomach pain (Livne et al., 2019). For a kid who is using to feel calmer, quitting hands him back a worse version of the exact discomfort he was trying to escape. That is one reason "just stop" is so much easier to say than to do.
Does THC Help With Anxiety?
The biggest story I told myself was that the weed was helping his anxiety. He was an anxious kid, suffering with it since he was a toddler. If it took the edge off, maybe it was doing a job a prescription, like an SSRI, would otherwise have to do. A lot of parents find themselves here. Isn’t weed better than taking a pill, which has it’s own negative side-effects?
The research tells a more complicated story, and not a reassuring one. THC has what scientists call a biphasic, dose-dependent effect on anxiety. At low doses it can dull anxiety briefly. At higher doses it does the opposite, reliably producing anxiety and sometimes outright panic (Sharpe et al., 2020). In a market built on high-potency flower and concentrates, the calming dose and the anxiety-producing dose are not far apart, and a daily user chasing relief is very often on the wrong side of that line.
Over time the picture gets worse, not better. Regular use is associated with more frequent anxiety, not less, and the relief becomes a loop: use to quiet the anxiety, feel calmer for an hour, then feel it return harder as the dose wears off and the brain's own regulation stays suppressed. The Kaiser study that followed those hundreds of thousands of teenagers found that cannabis use was associated with later anxiety disorders, on top of the psychosis and bipolar findings (Young-Wolff et al., 2026). And the withdrawal I just described closes the trap: when an anxious kid tries to stop, anxiety is one of the first symptoms to come roaring back, which sends him right back to the thing that is making it worse.
The bullet we dodged: Cannabinoid hyperemesis syndrome vs. psychosis
My son never became psychotic. He was one of the lucky ones, and so were we.
What we got instead was cannabinoid hyperemesis syndrome, a condition that shows up in long-term heavy users as cycles of severe nausea, vomiting, and abdominal pain (Cannabinoid Hyperemesis Syndrome, StatPearls, 2023). It is cruelly paradoxical, given that cannabis is marketed to settle the stomach, and it is widely missed by doctors who aren't looking for it. It made my son so sick that he was in and out of the hospital, and one night, from the organ strain that comes with relentless vomiting and diarreah, he nearly died. I still get a pit in my stomach thinking about the call I received from the attending doctor, “We will do everything in our power to save him, but right now his organs are shutting down.” The only reliable treatment is to stop using entirely.
I have lived that nightmare, the kind where you are grateful that the thing nearly killing your child is his body and not his mind. He got sick and tired of being sick and tired. His brain is his own.
I still wonder what years of heavy use during such a critical window did to him. He has not had a neuropsychological evaluation in a while. It would probably tell me something. A large part of me does not want to know.
If I knew then what I know now: Hindsight is 20/20
If I had understood that my son could have lost his mind, I would not have been as laissez-faire as I was. I was not happy about his use. But I did not do everything in my power to end it. Knowing what I know now, I would have been diehard. Drug testing. Clean screens as the condition of my financial support: I will pay for your phone, your food, and a roof, as long as the screens are clean, and if they are not, then treatment is required. I would have set boundaries firm enough to strain our relationship, maybe firm enough that he stopped speaking to me for a while.
Most parents are afraid of that path, and I understand the fear intimately. What if he leaves? What if he goes to the streets and finds something worse, like heroin or meth? Those fears are real, and no one should pretend otherwise. But if I had truly understood what those years of high-potency THC might have cost him, I would have walked that path anyway. The relationship can be repaired. A brain that breaks during the years it is still forming may not be.
I want to be careful here, because every family and every child is different, and a hard-boundary approach is not a formula you apply blindly. What it requires is that you make the decision with clear eyes, knowing what is actually at stake, instead of telling yourself the comfortable thing. That is the part I got wrong. Not the love. The information. (I've written more about how to think through that decision in When Your Child Isn't Safe: A Parent's Guide to Making a Really Hard Decision.)
what to do if your adolescent or young adult is using cannabis (thc)
If there is a young person in your life using cannabis, the questions worth asking are not whether it's "just weed," but how old they are, how potent the products are, and how often they're using. The younger the brain, the more potent the product, and the more frequent the use, the higher the stakes. These are conversations worth having early, and worth having from a place of information rather than fear.
There is shame in writing some of this, the plain shame of not having known what I did not know. I am writing it anyway, because I would rather a few more parents learn it from me than learn it the way Laura Stack did. Listening to her on that drive, I felt an old fire come back. I have not written about this in a while. She reminded me why I started.
Listen and learn more
Schizophrenia: Three Moms in the Trenches, the podcast that started this for me, hosted by Randye Kaye, Mindy Greiling, and Miriam Feldman. Available on Apple Podcasts, Spotify, and the show's home page. Their episode on cannabis and psychosis is the one to start with.
Johnny's Ambassadors, Laura Stack's nonprofit, with parent resources, a weekly webinar series, and Johnny's full story
If you or someone you love is struggling, the 988 Suicide and Crisis Lifeline is available by call or text at 988.
If your family is somewhere in the middle of this, you are not alone in it. This is the work we do every day at Crossbridge, and if you're in it, you don't have to figure it out by yourself. Just hit reply, or reach out here.
Jennifer Benson, MSW, is a partner at Crossbridge Consulting, a therapeutic educational consulting firm that helps families navigate complex school and treatment placements for children, adolescents, and young adults. She is a member of IECA, TCA, and YATA. Learn more about Jennifer.
sources on thc and the adolescent brain
Young-Wolff KC, Cortez CA, Alexeeff SE, et al. Adolescent Cannabis Use and Risk of Psychotic, Bipolar, Depressive, and Anxiety Disorders. JAMA Health Forum. 2026;7(2):e256839. doi:10.1001/jamahealthforum.2025.6839
Di Forti M, Quattrone D, Freeman TP, et al. The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): a multicentre case-control study. Lancet Psychiatry. 2019;6(5):427-436. doi:10.1016/S2215-0366(19)30048-3
Myran DT, Pugliese M, Harrison LD, et al. Changes in Incident Schizophrenia Diagnoses Associated With Cannabis Use Disorder After Cannabis Legalization. JAMA Network Open. 2025;8(2):e2457868. doi:10.1001/jamanetworkopen.2024.57868
McDonald AJ, Kurdyak P, Rehm J, Roerecke M, Bondy SJ. Age-dependent association of cannabis use with risk of psychotic disorder. Psychological Medicine. 2024;54(11):2926-2936. doi:10.1017/S0033291724000990
Bahji A, Stephenson C, Tyo R, Hawken ER, Seitz DP. Prevalence of Cannabis Withdrawal Symptoms Among People With Regular or Dependent Use of Cannabinoids: A Systematic Review and Meta-analysis. JAMA Network Open. 2020;3(4):e202370. doi:10.1001/jamanetworkopen.2020.2370
Livne O, Shmulewitz D, Lev-Ran S, Hasin DS. DSM-5 cannabis withdrawal syndrome: Demographic and clinical correlates in U.S. adults. Drug and Alcohol Dependence. 2019;195:170-177. doi:10.1016/j.drugalcdep.2018.09.005
Sharpe L, Sinclair J, Kramer A, de Manincor M, Sarris J. Cannabis, a cause for anxiety? A critical appraisal of the anxiogenic and anxiolytic properties. Journal of Translational Medicine. 2020;18:374. PMC7531079
Testai FD, Gorelick PB, Aparicio HJ, et al. Use of Marijuana: Effect on Brain Health. A Scientific Statement From the American Heart Association. Stroke. 2022;53(4):e176-e187. doi:10.1161/STR.0000000000000396
Volkow ND, Baler RD, Compton WM, Weiss SRB. Adverse Health Effects of Marijuana Use. New England Journal of Medicine. 2014;370:2219-2227. doi:10.1056/NEJMra1402309
Cannabinoid Hyperemesis Syndrome. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023. NCBI Bookshelf NBK549915
National Institute on Drug Abuse. Cannabis (Marijuana) research reports and DrugFacts (THC pharmacokinetics, storage in adipose tissue, and detection windows in chronic users). nida.nih.gov
