Bold claim: A landmark study links teen cannabis use to higher odds of serious mental health disorders years later. And this is the part most people miss: the implications stretch beyond individual risk to public health and policy.
As teen cannabis use has risen over the past decade, researchers have sought to clarify the health consequences. A new longitudinal study now indicates that adolescent cannabis use is associated with increased chances of later diagnoses of bipolar disorder, psychotic disorders, anxiety, and depression.
Columbia University psychiatrist Dr. Ryan Sultan, a cannabis researcher not involved in the study, calls the findings highly concerning. The research appears in the latest JAMA Health Forum.
A strong study design
Researchers analyzed health data from 460,000 teenagers within the Kaiser Permanente Health System in Northern California, tracking them until age 25. The dataset included annual substance-use screenings and recorded mental health diagnoses. Importantly, the researchers excluded youths who already showed mental-health symptoms before cannabis use.
We looked at kids who used cannabis before any psychiatric symptoms and followed them to see if they were more likely to develop these conditions later, explains Dr. Lynn Silver of the Public Health Institute, who co-authored the study.
Findings show that teens reporting cannabis use in the past year faced higher risks of several mental health conditions a few years down the line, compared with peers who did not use cannabis.
Two particularly serious outcomes stood out: bipolar disorder, characterized by fluctuating depressive and manic episodes, and psychotic disorders, including schizophrenia, which involve a break from reality. Among all teens in the study, these diagnoses remained relatively rare—roughly 4,000 cases each—but they are among the most disabling mental illnesses.
“These are the scarier conditions we worry about,” Sultan notes.
Silver adds that these illnesses are costly to treat and impose a heavy societal burden. While the U.S. cannabis market is worth tens of billions, the societal cost of schizophrenia has been estimated at about $350 billion annually. If more people develop this outcome in a preventable way, it could erode the market’s value, she argues.
Depression and anxiety are also more common among cannabis-using teens. Depression risk rose by about one-third, and anxiety by about one-quarter. The association with depression and anxiety weakened as tobacco age of cannabis use increased, underscoring the particular vulnerability of younger brains. The developing brain’s receptors appear especially sensitive to cannabis, affecting neurological development and raising the likelihood of these disorders.
Silver hopes the findings will curb teen cannabis usage by countering the perception that legalization makes cannabis a safe, natural product for stress. “With legalization, there’s a strong belief of safety,” she says. “That is simply not true.”
The study is cited for its solid design and its attempt to disentangle cause and effect—the chicken-or-egg question—by excluding youths with prior mental health symptoms. While prior research has shown links between cannabis use and mental health outcomes, it often couldn’t determine whether cannabis increased risk or people with preexisting problems used cannabis as a coping mechanism. By removing those with early symptoms, this study strengthens the case for a causal connection, though more research is needed.
“Playing with fire,” warns Sultan. He notes that his clinical experience mirrors the study: more teens are presenting with new or worsening anxiety, depression, and, increasingly, bipolar disorder and psychosis after cannabis onset.
Mental health disorders arise from a mix of factors—genetics, environment, lifestyle, and life experiences—and some youths are more vulnerable than others. If a psychotic or manic episode occurs in the context of cannabis use, clinicians caution against repeating it, as repeated exposure may worsen symptoms and hinder recovery. In essence, chronic cannabis use could accelerate neurobiological changes associated with these conditions, making long-term improvement harder to achieve.
Bottom line: the potential for harm is real, especially for younger adolescents, and this has broad implications for individuals, families, and health systems. Do you think current policies and teen-education efforts strike the right balance between decriminalization, medical access, and protective messaging for youths? What additional safeguards would you propose to protect developing brains while respecting adult access and autonomy?
