Cannabis use in adolescence was associated with a significantly greater likelihood of developing serious psychiatric disorders — particularly psychosis and bipolar disorder — in early adulthood compared to no cannabis use, a large longitudinal cohort study found.

Researchers analyzing electronic health record data from nearly 500,000 adolescents found that teens who reported past-year cannabis use were twice as likely to be diagnosed with psychotic or bipolar disorders as those who did not use cannabis. They also experienced more modest increases in diagnoses of depression and anxiety.

“This cohort study found that adolescent cannabis use was associated with increased risk of incident psychiatric disorders, particularly psychotic and bipolar disorders,” Kelly C. Young-Wolff, PhD, MPH, of Kaiser Permanente Northern California, and colleagues wrote. The findings are “consistent with cannabis being a risk factor for or exacerbating the risk of psychiatric disorders rather than only resulting from preexisting psychiatric conditions.”

The authors said the findings add to growing evidence that should inform clinical guidance, parent and adolescent education, and policies aimed at preventing or delaying youth cannabis use as legalization expands.

The study was published online on February 20 in JAMA Health Forum.

Closer Look at Teen Cannabis Use

As of early 2026, nearly half of the US states have legalized recreational marijuana use, and 38 states permit medical marijuana, according to the National Conference of State Legislatures.

The authors have noted a substantial rise in cannabis potency over recent decades, with average tetrahydrocannabinol (THC) concentrations in Northern California flower now exceeding 20%. 

THC binds to cannabinoid-1 receptors, which are highly expressed in the adolescent brain and may disrupt neural circuits involved in emotional regulation and cognition during a critical developmental window. 

While previous research has suggested a link between cannabis use and psychiatric illness, most of the data are based on small studies in adults or individuals with heavy, regular cannabis use.

To better understand the issue in teens, researchers conducted a retrospective analysis that included 463,396 adolescents aged 13-17 years who completed confidential cannabis screening during routine pediatric visits at Kaiser Permanente Northern California between 2016 and 2023. The cohort was nearly evenly divided between males (50.5%) and females (49.4%).

The researchers followed participants through age 25. 

Risk Tied to Any Past-Year Use

At baseline, 5.7% of participants reported cannabis use in the previous 12 months. 

During follow-up, more than 4000 adolescents were diagnosed with psychotic disorders and a similar number with bipolar disorder, while anxiety and depressive disorders were diagnosed in tens of thousands.

Psychiatric diagnoses typically followed the first report of cannabis use by an average of 1.7 to 2.3 years. 

After adjusting for demographic factors, socioeconomic status, prior mental health conditions, and other substance use, past-year cannabis use was associated with more than double the likelihood of psychotic disorders (adjusted hazard ratio [AHR], 2.19) and bipolar disorder (AHR, 2.01).

Associations were smaller but remained significant for depressive (AHR, 1.34) and anxiety disorders (AHR, 1.24).

Even adolescents who reported any cannabis use in the prior year — not necessarily daily or heavy use — showed similarly elevated likelihood of later psychotic and bipolar diagnoses.

“Given that daily cannabis use and use of higher strength cannabis products may have a stronger association with psychiatric disorders, it is notable that we found associations even when defining cannabis solely as any past-year use,” researchers wrote.

Findings Key for Public Health

Baseline cannabis use was more prevalent among older adolescents, Hispanic, non-Hispanic Black, and non-Hispanic White teens, as well as among those with Medicaid or those living in socioeconomically disadvantaged areas. 

The authors noted that these patterns raise equity concerns amid rising cannabis accessibility and commercialization. 

“Increasing evidence on the associations of adolescent cannabis use with increased risk of developing psychiatric disorders could inform more effective policies to limit youth access, marketing, and exposure in legal cannabis markets,” they wrote, urging stronger public health messaging and early prevention efforts.

Although causality cannot be established, the association with later psychiatric diagnoses remained consistent across multiple sensitivity analyses, investigators noted.

The authors acknowledged several limitations. Cannabis use was self-reported and did not capture frequency, mode of use, or detailed potency exposure. Psychiatric diagnoses were based on electronic health records and may have missed undiagnosed cases. 

Although cannabis use preceded diagnosis by nearly 2 years on average, unmeasured confounding, including genetic vulnerability or early childhood adversity, cannot be ruled out.

The study was funded by a grant from the National Institute on Drug Abuse. The funder had no role in the study design or reporting. Full author disclosures are detailed in the original article.