Can Teen Cannabis Use Increase the Risk of Mental Illness?
Yes. A large study of over 463,000 adolescents found that teens who used cannabis were more than twice as likely to develop psychotic or bipolar disorders later in life. They were also 34% more likely to develop depression and 24% more likely to develop anxiety.
This study, published in JAMA Health Forum, followed hundreds of thousands of teens aged 13 to 17 over time. Researchers tracked whether those who reported past-year cannabis use went on to receive a psychiatric diagnosis. The results paint a concerning picture for parents and teenagers alike, especially as cannabis becomes more widely available and socially accepted across the country.
What makes these findings so striking is the timeline. Cannabis use typically came first, appearing an average of 1.7 to 2.3 years before a psychiatric diagnosis showed up. While this does not prove that cannabis directly caused the mental health problems, the pattern is hard to ignore.
Dr. Kumar’s Take
I find this study deeply important, especially as a physician who sees young patients. The size of this study alone, over 463,000 teens, gives it real weight. The fact that cannabis use came before the diagnosis in most cases by nearly two years is a strong signal that something is happening in the developing brain.
I want to be clear: this study cannot prove that cannabis caused these disorders. There may be shared risk factors we do not yet understand. But when I see a teenager whose risk of developing a psychotic disorder more than doubles with cannabis use, that is a conversation every parent and pediatrician needs to have. The teenage brain is still forming, and substances that affect brain chemistry during this window may carry risks that do not apply to adults.
What the Data Show
The numbers from this study are hard to overlook. Among the 463,396 adolescents studied, those who reported cannabis use in the past year faced more than double the risk of developing a psychotic or bipolar disorder compared to teens who did not use cannabis. The risk of depression was 34% higher, and anxiety risk was 24% higher.
One of the most interesting patterns was how these risks changed with age. The link between cannabis and depression or anxiety grew weaker as teens moved into their early twenties. By ages 21 to 25, the connection was no longer statistically significant for those conditions. This suggests the adolescent brain may be especially vulnerable to the effects of cannabis in ways that the adult brain is not.
Who Is Most at Risk?
The strongest associations appeared in the youngest group, teens aged 13 to 17. This makes sense given what we know about brain development. The prefrontal cortex, the part of the brain responsible for decision-making, impulse control, and emotional regulation, does not fully mature until the mid-twenties. Introducing cannabis during this critical window may interfere with normal development in ways that raise the risk of serious mental health conditions.
The link to psychotic and bipolar disorders was especially strong, and unlike depression and anxiety, this connection did not weaken with age. This suggests that the most severe psychiatric outcomes may involve different pathways than mood and anxiety disorders, and those pathways may be more permanently affected by early cannabis exposure.
Important Limitations
This study has real strengths, including its massive sample size and its long follow-up period. But there are important things it cannot tell us. Because it is an observational study, not an experiment, it cannot prove that cannabis use caused the psychiatric diagnoses. It is possible that teens already developing early symptoms of mental illness turned to cannabis as a form of self-medication before their condition was formally diagnosed.
The study also relied on self-reported cannabis use, which means some teens may have underreported or overreported their usage. Researchers could not account for how often teens used cannabis, the strength of the products they used, or whether they combined cannabis with other substances.
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.
- 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 psychotic disorders, but it could not prove direct causation. It is possible that some teens who later developed psychosis were already showing subtle early symptoms and turned to cannabis before receiving a formal diagnosis. However, the consistent finding across many large studies that cannabis use precedes psychotic episodes, often by years, has led many researchers to consider it a significant contributing risk factor. The current scientific consensus is that cannabis likely interacts with genetic and environmental vulnerabilities to increase psychosis risk, rather than acting as a sole cause.
Is cannabis safer for adults than for teenagers?
The data from this study suggest yes, at least when it comes to depression and anxiety risk. The association between cannabis use and these conditions was strongest in teens aged 13 to 17 and weakened significantly by ages 21 to 25, when it was no longer statistically significant. This aligns with what neuroscientists know about brain development. The adolescent brain is undergoing major changes in areas that control mood, reward, and decision-making. Substances that disrupt these processes during this sensitive period may carry risks that simply do not apply once the brain has finished developing. That said, adult cannabis use is not without risk, especially for those with a family history of psychotic disorders.
Should parents be concerned if their teen has only tried cannabis once or twice?
This study measured past-year cannabis use, not lifetime use, so it captured teens who were at least occasional users. It did not break down risk by frequency or amount. A single experiment with cannabis is unlikely to carry the same risk as regular use. However, adolescence is a time when occasional use can quickly become habitual, especially given the high potency of many modern cannabis products. Parents should view any use as a starting point for conversation, not as something to dismiss. Early and open discussions about the real risks, backed by data like this study, are one of the most effective ways to help teens make informed decisions.
Bottom Line
A study of over 463,000 teenagers found that adolescent cannabis use was linked to more than double the risk of psychotic or bipolar disorders, a 34% higher risk of depression, and a 24% higher risk of anxiety. The connection was strongest in the youngest teens and weakened by young adulthood for mood and anxiety conditions, but not for psychotic disorders. While the study cannot prove causation, the size of the data and the consistent timing pattern, where cannabis use preceded diagnosis by nearly two years, make a strong case that the developing teenage brain is particularly vulnerable to the effects of cannabis.
