Can Teen Cannabis Use Increase the Risk of Mental Illness?
Yes. A cohort study of 463,396 adolescents found that teens who reported cannabis use in the past year were more than twice as likely to be diagnosed with a psychotic or bipolar disorder by age 26. The risk of depressive and anxiety disorders was elevated as well, though by a smaller margin.
This was a retrospective cohort study of adolescents aged 13 to 17 at Kaiser Permanente Northern California. Between 2016 and 2023, teens answered a confidential screening question about past-year cannabis use during routine well-child visits, and researchers then followed them through their electronic health records until age 25 or the end of 2023. Because the screening is universal rather than triggered by concern, the cohort captures ordinary teenagers coming in for a check-up, not a clinic population already flagged for substance use.
The exposure was updated every time a teen answered the question again at a later visit, and any adolescent already carrying a given diagnosis at baseline was dropped from the analysis of that outcome. So the diagnoses being counted are new ones that followed the cannabis screening.
Dr. Kumar’s Take
I find this study important, especially as a physician who sees young patients. The size alone, over 463,000 teens screened during routine pediatric care, gives it real weight, and the psychiatric outcomes are clinician-assigned diagnoses rather than symptom questionnaires.
I want to be clear: this study cannot prove that cannabis caused these disorders. There may be shared risk factors I do not yet understand, and the authors themselves note that not every study has found cannabis to be a factor. But when the risk of a psychotic or bipolar diagnosis roughly doubles in the teens who report using, that is a conversation every parent and pediatrician needs to have. The teenage brain is still forming, and substances that act on brain chemistry during this window may carry risks that do not apply in the same way to adults.
What the Data Show
Among the 463,396 adolescents in the cohort, 26,345 (5.7%) reported past-year cannabis use at their first screening. After adjustment for sex, race and ethnicity, neighborhood deprivation, insurance type, and time-varying alcohol and other substance use, past-year cannabis use was associated with:
- Psychotic disorders: adjusted hazard ratio 2.19 (95% CI, 1.97 to 2.42)
- Bipolar disorders: adjusted hazard ratio 2.01 (95% CI, 1.82 to 2.22)
- Depressive disorders: adjusted hazard ratio 1.34 (95% CI, 1.30 to 1.39)
- Anxiety disorders: adjusted hazard ratio 1.24 (95% CI, 1.21 to 1.28)
The researchers then added a further adjustment for past psychiatric conditions, which is the analysis I care about most, since it partly addresses the worry that early symptoms drove the cannabis use rather than the reverse. The pattern held with slight attenuation: psychotic disorders 1.92 (1.73 to 2.13), bipolar disorders 1.73 (1.57 to 1.90), depressive disorders 1.33 (1.29 to 1.38), and anxiety disorders 1.19 (1.16 to 1.23).
One age pattern did emerge. The strength of the associations between cannabis use and incident depressive and anxiety disorders decreased as the adolescents got older.
Who Is Most at Risk?
Everyone in this cohort was between 13 and 17 years old at screening, so the study describes adolescent exposure as a whole rather than comparing teens against adults.
Cannabis use also travelled with other exposures. Among teens who reported past-year cannabis use, 64.3% also reported drinking alcohol in the past year, compared with 3.3% of those who did not use cannabis, and 22.7% reported using another substance to get high, calm down, or stay awake, compared with 0.9%. A history of disruptive behavior disorder was present in 8.7% of cannabis users versus 3.9% of non-users. The models adjusted for alcohol and other substance use, but these figures tell me that a teen who says yes to cannabis is often a teen worth asking several more questions.
The associations with psychotic and bipolar disorders were the largest of the four outcomes.
Important Limitations
This study has real strengths, including its size, its universal screening design, and diagnoses drawn from clinical records rather than self-report. But there are important things it cannot tell me. Because it is observational, it cannot prove that cannabis use caused the psychiatric diagnoses. It remains possible that teens already developing early symptoms turned to cannabis before their condition was formally diagnosed, which is exactly why the additional adjustment for past psychiatric conditions matters, and why the persistence of the association after that adjustment is meaningful without being conclusive.
The exposure was a single confidential yes or no question about the past year, answered by the teen. Self-report can go either direction, and a yes from a teenager who tried cannabis once is scored the same as a yes from one who uses daily. Follow-up also stopped at age 25, so the cohort was observed through adolescence and young adulthood rather than across a full lifetime.
Practical Takeaways
- Talk openly with your teenagers about what this research shows, because the risks of cannabis use during adolescence appear to go well beyond what most families realize.
- If your teen is already using cannabis, speak with their pediatrician or a mental health professional about screening for early signs of mood or psychotic disorders.
- Pay attention to changes in behavior, sleep, social withdrawal, or unusual thinking patterns in teens who may be using cannabis, as these could be early warning signs.
- Ask about alcohol and other substances too, since in this cohort they clustered heavily with cannabis use.
- Remember that the legal status of cannabis in your state does not reflect its safety for developing brains, and legal does not mean risk-free for adolescents.
Related Studies and Research
If you are interested in learning more about mental health and substance use in young people, these related articles explore similar themes:
- Over-the-counter products for depression, anxiety, and insomnia in older adults looks at how common supplements and OTC products are used for mental health across age groups.
- Sugary drinks linked to 34% higher anxiety risk in teens examines another modifiable risk factor for anxiety in adolescents.
- Circadian light therapy for young people with depression: systematic review explores a non-drug approach to treating depression in younger populations.
- Dietary creatine intake and depression risk among U.S. adults covers nutritional factors that may influence mood disorders.
FAQs
Does cannabis directly cause psychosis in teenagers?
This study found a strong association between adolescent cannabis use and later psychotic disorder diagnoses, with an adjusted hazard ratio of 2.19, but an observational cohort cannot establish direct causation. Some teens who later developed psychosis may have been showing subtle early symptoms and turned to cannabis before receiving a formal diagnosis. The authors addressed that concern in part by re-running the models with adjustment for past psychiatric conditions, and the association was attenuated but still present at 1.92. They also note that prior longitudinal work has linked early adolescent use, daily use, cannabis use disorder, and higher strength products to psychotic disorders, while acknowledging that not all studies report cannabis as a factor in increased risk. My reading is that cannabis is best treated as a contributing risk factor that interacts with other vulnerabilities, not as a sole cause.
Is cannabis safer for adults than for teenagers?
This study cannot answer that directly, because everyone in it was screened between ages 13 and 17 and followed only to age 25. What it does show is that the strength of the associations between cannabis use and incident depressive and anxiety disorders decreased as the adolescents aged. That fits what neuroscientists describe about brain development: the adolescent brain is undergoing major changes in the systems that govern mood, reward, and decision-making, and substances that act on those systems during the sensitive period may carry risks that differ from those in a fully developed brain. That is not a clearance for adult use, particularly for anyone with a family history of psychotic disorders.
Should parents be concerned if their teen has only tried cannabis once or twice?
The exposure here was a single question, whether the teen used marijuana during the past year, so a yes covers everything from one experiment to regular use, and the results describe that group as a whole. What the cohort does show is that cannabis use clustered tightly with alcohol and other substance use. Adolescence is a period when occasional use can become habitual, especially given the potency of modern cannabis products. I would treat any use as a reason to start a conversation, not as something to wave off.
Bottom Line
In a cohort of 463,396 adolescents screened for cannabis use during routine pediatric visits, past-year use was associated with roughly double the risk of an incident psychotic disorder (adjusted hazard ratio 2.19) or bipolar disorder (2.01), along with smaller but clear increases in depressive (1.34) and anxiety (1.24) disorder diagnoses through age 26. The associations with depression and anxiety weakened as the teens got older, and all four held up with modest attenuation after additional adjustment for past psychiatric conditions. The study cannot prove causation, but the size of the cohort, the universal screening, and the use of clinician-assigned diagnoses make this a serious signal that the developing teenage brain is particularly vulnerable to cannabis.
