Teenage cannabis users twice as likely as non-users to develop psychosis, bipolar disorder

A large and longitudinal study has added a trove of hard data to a widely held hypothesis about young people, cannabis and mental illness: Users are much more likely than non-users to be diagnosed with disorders of the mind. 

The new work doesn’t solve the mystery of which tends to come first—the illness or the drug use. 

Regardless, the research serves to underscore the need for proactive clinical, educational and protective measures—especially in this time of broad decriminalization and societal tolerance for “weed” usage. 

The researchers flesh out the major takeaways and discuss their full findings in a study published Feb. 20 in JAMA Health Forum. 

Teen cannabis use a red flag for susceptibility 

The team, led by clinical psychologist and senior scientist Kelly Young-Wolff, PhD, MPH, and colleagues at Kaiser Permanente Research, analyzed the records of approximately 464,000 adolescents who were initially screened for cannabis use when they were 13 to 17 years old. 

The researchers continued their investigative tracking until the participants reached their mid-20s.   

Most strikingly, Young-Wolff and team found cannabis use corresponded with doubled rates of both psychotic and bipolar disorders by young adulthood. 

Depressive and anxiety conditions were elevated in the user cohort too, albeit not as dramatically.

In their discussion section, Young-Wolff and co-authors note their use of population-level, EHR-based clinical data.

They state the results are “consistent with cannabis being a risk factor for—or exacerbating the risk of—psychiatric disorders rather than only resulting from preexisting psychiatric conditions.”

Further, they remark, the findings “reinforce the need for early prevention efforts, stronger public health messaging and policy strategies that limit youth exposure in the context of expanding cannabis legalization.”

This is not your grandparents’ pot party  

In consumer coverage of the study by Kaiser Permanente’s news operation, the researchers note the high average concentration of the psychoactive agent tetrahydrocannabinol (THC) in today’s cannabis versus that of decades past.

They also acknowledge the lack of a smoking gun that would show a cause-and-effect link between cannabis use and later mental illness. 

The study’s senior author, Stacy Sterling, DrPH, MSW, MPH, says that, while the project didn’t answer the question of causality, it “adjusts carefully for previous mental health problems and moves the field forward towards establishing a chronology of problem development.”

Sterling and Young-Wolff add that cannabis has not been shown to be an effective treatment for depression or anxiety. In fact, they emphasize, ongoing use of the substance is associated with worsening mood symptoms and poorer adherence to behavioral health treatment. Their implied warning: Those who turn to cannabis expecting mental relief may experience the exact opposite. 

Read the journal study here.