It is no secret that many young people believe that marijuana is a safe and natural drug and is the most commonly tried illegal drug in New Zealand. However, recent research has revealed otherwise. A recent study found that cannabis use among adolescents increases the risk of being diagnosed with bipolar and psychotic disorders, as well as anxiety and depression, years later.
Published in the latest JAMA Health Forum, the longitudinal study analysed health data on 460,000 teenagers (aged 13-17 years) in the Kaiser Permanente Health System in Northern California, USA, and followed them until they reached age 25. Researchers found that cannabis use was associated with a significantly increased risk across all four psychiatric outcomes compared to non-users by the time participants were 25 years old. For adolescent cannabis users, the risk for psychotic disorders was 2x higher, bipolar disorder was 2x higher, depressive disorders were 1.3x higher, and anxiety disorders were 1.2x higher than for non-users.
The study’s findings appear consistent with other longitudinal epidemiological research showing that adolescent cannabis use is often associated with a higher risk of psychotic experiences and disorders in adulthood. This includes experimental studies reporting increased psychotic experiences following intravenous tetrahydrocannabinol (THC) exposure. While other studies have also found a link between cannabis use and mental health conditions, determining a causal relationship has often been difficult.
However, this latest research has excluded teenagers already exhibiting mental health symptoms, suggesting a potential causal link between cannabis use and subsequent mental health diagnoses.
The study is well-designed and addresses the classic cause-and-effect question: which comes first? Psychiatrist Dr Ryan Sultan at Columbia University, a cannabis researcher not involved in the study, notes that it tackles the ‘chicken-or-the-egg, order-of-operations question”. Past research has also shown a link between cannabis use and mental health issues, especially psychosis. However, those studies couldn’t clarify whether cannabis use increased the risk of developing mental health symptoms or whether individuals with existing issues were more inclined to use cannabis, possibly to manage their symptoms.
Whilst further studies are needed to fully understand this link, the new findings underscore the harmful effects of marijuana, particularly on the adolescent brain, which is still developing neurologically, cognitively and emotionally.
*Written by Family First staff writers*
