For many parents, cannabis can seem like a relatively harmless part of teenage experimentation. Some remember trying it themselves when they were younger, while others assume that occasional use is unlikely to cause serious problems.
But a major American study suggests that cannabis use during adolescence may be associated with greater mental health risks than many families realize.
Researchers examining the medical records of more than 463,000 teenagers found that those who reported using cannabis were approximately twice as likely to later be diagnosed with certain serious psychiatric conditions.
The strongest connections involved psychotic disorders and bipolar disorder, although researchers also identified increased risks of depression and anxiety.
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According to Kaiser Permanente's official announcement, the findings raise important questions about how cannabis may affect the developing brain, particularly when use begins at a young age.
The research was published in JAMA Health Forum on February 20, 2026, and is among the largest studies to examine the relationship between teenage cannabis use and subsequent psychiatric diagnoses.
Researchers followed more than 463,000 teenagers
The study was conducted by researchers at Kaiser Permanente Northern California, who examined health information from 463,396 adolescents between the ages of 13 and 17.
Rather than relying on adults remembering what they had done as teenagers, the researchers used information collected during routine medical appointments.
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Between 2016 and 2023, the teenagers completed confidential questionnaires asking whether they had used cannabis during the previous year.
Approximately 26,345 participants, equivalent to 5.7 percent of the study population, reported having used cannabis.
Researchers then examined their medical records to identify whether they subsequently received a diagnosis of a psychotic, bipolar, depressive or anxiety disorder.
Participants were followed until they received a relevant diagnosis, left the healthcare system, reached age 25 or the study ended in December 2023.
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The average follow-up lasted approximately three to four years, meaning not every participant was observed until their mid-twenties.
This approach allowed researchers to investigate whether cannabis use was recorded before the appearance of a clinically diagnosed mental health condition.
The results revealed several concerning patterns.
Cannabis users had approximately twice the risk of two serious disorders
When researchers compared teenagers who reported cannabis use with those who did not, they found significantly higher rates of several psychiatric diagnoses.
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The strongest associations involved psychotic disorders and bipolar disorder.
Teenagers who reported using cannabis had:
- A 119% higher relative hazard of receiving a psychotic disorder diagnosis.
- A 101% higher relative hazard of receiving a bipolar disorder diagnosis.
- A 34% higher relative hazard of receiving a depressive disorder diagnosis.
- A 24% higher relative hazard of receiving an anxiety disorder diagnosis.
These figures came from statistical analyses that accounted for several differences between participants, including age, sex, socioeconomic factors, alcohol use and other substance use.
The results were particularly striking for psychotic disorders.
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Psychosis involves a disruption in how someone experiences or interprets reality. Symptoms can include hallucinations, such as hearing voices, or delusions, which are strongly held beliefs that do not match reality.
Psychosis can occur in several psychiatric conditions, including schizophrenia, but receiving a diagnosis of a psychotic disorder does not automatically mean someone has schizophrenia.
Bipolar disorder is different. It involves episodes of significant mood changes, including depression and periods of unusually elevated or irritable mood known as mania or hypomania.
The study's findings suggest that teenagers reporting cannabis use were more likely to develop these diagnoses during follow-up.
However, the figures describe relative differences in the rate of new diagnoses, not the probability that an individual teenager will develop a psychiatric disorder.
Most participants, including those who reported cannabis use, did not receive a psychotic or bipolar disorder diagnosis during the study.
The youngest teenagers showed another concerning pattern
One of the most interesting findings involved the age at which teenagers were exposed to cannabis.
The researchers discovered that the association between cannabis use and depression or anxiety was particularly strong during early adolescence.
Among teenagers aged 13 to 15, cannabis use was associated with a 78 percent higher relative hazard of depression and a 47 percent higher relative hazard of anxiety.
Those associations became weaker as participants grew older.
By ages 21 to 25, the researchers no longer found statistically significant associations between cannabis use and new depression or anxiety diagnoses within those particular age-specific analyses.
However, the increased risk associated with psychotic and bipolar disorders remained evident into young adulthood.
This suggests that the relationship between cannabis use and mental health may differ depending on both a person's age and the psychiatric condition being examined.
Lead researcher Kelly Young-Wolff, a clinical psychologist and research scientist at Kaiser Permanente, emphasized the importance of adolescence when discussing the findings.
"These results add to growing evidence that adolescence may be a particularly vulnerable period for cannabis-related harms," she said.
The findings are especially relevant because the teenage years are a critical period of brain development.
Scientists believe THC may interfere with the developing brain
The human brain continues developing well beyond childhood, with important changes occurring throughout adolescence and early adulthood.
During this period, the brain strengthens connections that are frequently used while gradually removing others. This process helps develop the systems responsible for decision-making, memory, emotional regulation and other important functions.
Cannabis contains a psychoactive compound called tetrahydrocannabinol, commonly known as THC, which is responsible for many of the drug's intoxicating effects.
THC interacts with the body's endocannabinoid system, a network of receptors and chemical signals involved in regulating mood, memory, appetite and other functions.
One important component of this system is the CB1 receptor, which is found throughout the brain.
According to the US Centers for Disease Control and Prevention (CDC), cannabis exposure during adolescence may interfere with brain development, particularly when use is frequent or begins at a young age.
Researchers believe THC may affect the way certain brain circuits develop, potentially influencing emotional processing and the regulation of thoughts and behavior.
However, scientists are still investigating exactly how these biological effects relate to the development of psychiatric disorders.
The new Kaiser Permanente study did not directly measure changes in participants' brains, so it cannot establish that THC-related changes caused their later diagnoses.
Today's cannabis can be much stronger than parents remember
Another factor receiving increasing attention is the strength of modern cannabis products.
Cannabis available today can contain considerably higher concentrations of THC than products commonly used in previous decades.
The researchers noted that cannabis flower sold in Northern California now has an average THC concentration exceeding 20 percent.
This is important because previous studies suggest that frequent cannabis use and exposure to products containing more THC may be associated with greater psychiatric risks.
The CDC's guidance on cannabis and brain health also identifies THC concentration, frequency of use and age of first exposure as factors that may influence the drug's effects.
However, the Kaiser Permanente researchers did not measure which products individual teenagers used or how much THC they consumed.
The study therefore cannot determine whether stronger cannabis products were responsible for the associations observed.
It also cannot establish whether smoking cannabis, vaping it or consuming edible products produced different outcomes.
These questions will require further research.
Even reported cannabis use was linked to higher risk, but there is a catch
One particularly notable aspect of the study was that researchers did not limit their analysis to teenagers who used cannabis heavily.
Participants were simply asked whether they had used cannabis during the previous year.
This means the researchers identified an association using a broad measure that included anyone reporting past-year use, rather than restricting the study to daily users or people diagnosed with cannabis use disorder.
However, there is an important limitation.
The questionnaire did not establish how frequently each teenager used cannabis, how much they consumed or which products they used.
As a result, the study cannot prove that trying cannabis once carries the same risks as using it every day.
The researchers also acknowledged that teenagers who use cannabis frequently may be more willing to report their use than those who have only experimented occasionally.
This means the findings could partly reflect the experiences of more frequent users.
The distinction matters because the risks associated with cannabis are unlikely to be identical for every pattern of use.
Did cannabis cause the mental health problems?
This is perhaps the most important question raised by the study.
The researchers found that cannabis use generally came before the psychiatric diagnoses recorded in participants' medical histories.
Among teenagers who reported cannabis use and later received a diagnosis, the average time between those events ranged from approximately 1.7 to 2.3 years.
That timeline suggests cannabis could potentially contribute to the development of certain mental health problems.
However, it does not prove that cannabis caused those conditions.
For example, a teenager experiencing early symptoms of anxiety, depression or another psychiatric condition might begin using cannabis to cope with their emotions before receiving a formal diagnosis.
In that situation, cannabis use could appear in medical records before the diagnosis, even though the underlying mental health problem had already begun.
Genetic vulnerability, family circumstances, childhood adversity and other factors could also influence both cannabis use and psychiatric health.
To address some of these concerns, the researchers conducted additional analyses accounting for previous psychiatric conditions.
The associations became slightly weaker but remained statistically significant.
After those additional adjustments, cannabis use was associated with approximately 92 percent higher relative hazard of psychotic disorders and 73 percent higher relative hazard of bipolar disorder.
These findings strengthen the evidence of a relationship, but observational research cannot eliminate every possible alternative explanation.
The researchers therefore emphasize that more detailed studies are needed before the exact causal relationship can be established.
Other studies have raised questions about cannabis-related harms
The findings add to a broader body of research examining how cannabis use may affect mental and behavioral health.
Previous studies have reported connections between cannabis use and conditions such as depression, psychosis and substance use disorders.
Researchers have also investigated other outcomes, including a large analysis involving more than 265,000 people that examined cannabis use and violent behavior.
However, that research investigated a different outcome, and its findings should not be interpreted as evidence that people who use cannabis will become violent or that cannabis directly causes violence.
The relationship between substance use, behavior and mental health is complex, and many factors can contribute to the patterns observed in population studies.
Nevertheless, the accumulating evidence has led health organizations to pay particular attention to cannabis use among adolescents.
The CDC warns that the association between cannabis and schizophrenia appears stronger among people who begin using cannabis at a younger age and those who use it more frequently.
The new Kaiser Permanente study adds to those concerns by examining diagnosed psychiatric disorders in a particularly large teenage population.
What parents should do if their teenager uses cannabis
For parents, the findings may be concerning, but researchers emphasize that responding with anger or punishment is not necessarily the most effective approach.
Teenagers may use cannabis for many reasons, including curiosity, social pressure or attempts to manage difficult emotions.
Understanding those reasons can be an important first step toward providing support.
According to the American Academy of Pediatrics, parents should prioritize open and honest conversations rather than relying on threats or scare tactics.
Asking teenagers what they know about cannabis, whether their friends use it and how they feel about the potential risks may encourage more productive discussions.
Parents should also pay attention to persistent changes in mood, sleep, school performance or social behavior.
However, these changes do not automatically mean a teenager is using cannabis or developing a mental health disorder. They can have many explanations and should be approached with curiosity rather than assumptions.
If there are concerns about cannabis use, a pediatrician or another qualified healthcare professional can help assess the situation.
Doctors can provide confidential screening, discuss substance use and investigate whether a teenager may also be struggling with anxiety, depression or another mental health condition.
Young-Wolff and her colleagues argue that routine screening could help identify problems before they become more serious.
What the findings mean for teenagers and their families
The study does not suggest that every teenager who experiments with cannabis will develop a psychiatric disorder.
Nor does it establish that cannabis alone explains why some young people develop conditions such as psychosis, bipolar disorder or depression.
But the findings do provide another reason to take cannabis exposure during adolescence seriously.
The researchers found consistent associations between reported cannabis use and several later mental health diagnoses, even after accounting for multiple other factors.
The strongest relationships involved psychotic and bipolar disorders, while depression and anxiety showed particularly concerning patterns among younger teenagers.
For families, the practical message is not to panic over suspected cannabis use, but to make sure teenagers have accurate information, supportive adults and access to medical guidance when necessary.
The study also reinforces the importance of recognizing mental health problems early, particularly when substance use and emotional difficulties occur together.
Cannabis is often discussed as a relatively harmless recreational substance, especially as legalization becomes more widespread.
But for teenagers whose brains are still developing, the available research suggests the potential risks deserve careful attention.
And while scientists continue investigating exactly how cannabis and psychiatric conditions are connected, one conclusion remains important: delaying or avoiding cannabis use during adolescence is a reasonable way to reduce exposure to a potentially harmful risk factor.
This article is made and published by Aksel Kryhlmand, who may have used AI in the preparation.