Adolescent cannabis use is significantly linked to a doubled risk of developing psychotic and bipolar disorders, and a heightened risk of depression and anxiety, according to a large new study published in JAMA Health Forum. The research, which followed over 463,000 individuals from ages 13 to 26, adds to a growing body of evidence concerning the potential mental health consequences of early cannabis exposure.
The longitudinal study analyzed electronic health record data from routine pediatric visits between and . Researchers from Kaiser Permanente, the Public Health Institute, the University of California, San Francisco, and the University of Southern California collaborated on the project, which received funding from the National Institute on Drug Abuse (NIH grant R01DA0531920).
The study specifically found that adolescents who reported past-year cannabis use faced a doubled risk of developing psychotic disorders and bipolar disorder by young adulthood. The association with depressive and anxiety disorders was also significant, though the study did not quantify the increased risk to the same degree as with the psychotic and bipolar conditions.
“As cannabis becomes more potent and aggressively marketed, this study indicates that adolescent cannabis use is associated with double the risk of incident psychotic and bipolar disorders, two of the most serious mental health conditions,” said Lynn Silver, M.D., program director of the Getting it Right from the Start program at the Public Health Institute, and a study co-author.
The researchers observed that, on average, psychiatric diagnoses occurred between 1.7 and 2.3 years after adolescents reported cannabis use. This temporal relationship, while not proving causation, strengthens the argument that cannabis exposure may be a contributing factor in the development of these mental illnesses. The study’s longitudinal design – following the same individuals over time – is a key strength, as it allows researchers to observe the sequence of events and reduce the likelihood of reverse causation (where a pre-existing mental health condition leads to cannabis use, rather than the other way around).
It’s important to note that the study identifies an association between adolescent cannabis use and increased risk of mental health disorders, but does not definitively prove that cannabis causes these conditions. Other factors, such as genetic predisposition, family history of mental illness, and environmental stressors, also play significant roles in the development of psychiatric disorders. However, the findings suggest that cannabis use may act as a trigger or exacerbate existing vulnerabilities in some individuals.
The increasing potency of cannabis products available today is a particular concern. Modern cannabis strains often contain much higher levels of tetrahydrocannabinol (THC), the psychoactive compound responsible for the “high,” than those available in the past. Higher THC levels have been linked to a greater risk of adverse mental health effects, particularly in adolescents whose brains are still developing.
The study’s findings have important implications for public health and prevention efforts. Given the increasing legalization and commercialization of cannabis, it is crucial to educate adolescents, parents, and healthcare providers about the potential risks associated with early cannabis use. Preventing or delaying the initiation of cannabis use during adolescence may be an important strategy for reducing the burden of mental illness in young adults.
The researchers emphasize the need for continued research to better understand the complex relationship between cannabis use and mental health. Future studies should investigate the specific types of cannabis products used, the frequency and duration of use, and the individual characteristics that may make some adolescents more vulnerable to adverse effects. Further investigation into the underlying biological mechanisms linking cannabis exposure to mental illness is also warranted.
This study adds to a growing body of evidence suggesting that adolescent cannabis use is not without risk. While the debate surrounding cannabis legalization continues, these findings underscore the importance of prioritizing the mental health of young people and implementing evidence-based prevention strategies.
