A huge study finds a link between cannabis use in teens and psychosis later

Growing rates of marijuana use among adolescents are prompting increased scrutiny of the drug’s potential long-term health consequences. A new, extensive study reveals a link between cannabis use during teenage years and a heightened risk of developing serious mental health conditions – including bipolar and psychotic disorders, as well as anxiety and depression – years later.

A Concerning Trend

Psychiatrist Dr. Ryan Sultan at Columbia University, who was not involved in the research, described the findings as “very, very, very worrying.” The study, recently published in JAMA Health Forum, analysed health data from a large cohort of nearly 460,000 teenagers within the Kaiser Permanente Health System in Northern California.

Robust Research Methodology

Researchers followed these individuals until they reached age 25, tracking annual substance use screenings and mental health diagnoses recorded in their health records. Crucially, the study excluded adolescents who already exhibited symptoms of mental illness prior to cannabis use, allowing researchers to isolate the potential impact of the drug.

Dr. Lynn Silver, a pediatrician and researcher at the Public Health Institute and an author of the study, explained the research approach: “We looked at kids using cannabis before they had any evidence of these psychiatric conditions and then followed them to understand if they were more likely or less likely to develop them.”

Increased Risk of Serious Illness

The data revealed that teenagers who reported recent cannabis use faced a significantly elevated risk of being diagnosed with several mental health conditions in the years that followed. Specifically, cannabis use was associated with a doubled risk of developing bipolar disorder – characterized by alternating periods of depression and mania – and psychotic disorders, such as schizophrenia, which involve a detachment from reality.

While the number of teens diagnosed with these severe conditions remained relatively small – approximately 4,000 in the entire study – both bipolar and psychotic disorders are recognized as among the most debilitating mental illnesses.

Impact on Common Mental Health Concerns

The study also indicated a higher risk of more prevalent conditions like depression and anxiety among cannabis users. Depression rates increased by roughly one-third, while anxiety rates rose by about a quarter. However, the correlation between cannabis use and these conditions appeared weaker in teens who began using cannabis at an older age.

Dr. Silver emphasized the vulnerability of the developing adolescent brain, stating, “The brain is still developing. The effects of cannabis on the receptors in the brain seem to have a significant impact on their neurological development and the risk for these mental health disorders.”

Potential Future Implications

If these findings prompt increased caution among teenagers, it could lead to a decrease in cannabis use and, potentially, a reduction in the incidence of preventable mental health disorders. Conversely, continued widespread cannabis use, particularly among young people, may result in a greater burden on mental healthcare systems and increased societal costs associated with these illnesses. Further research is needed to fully understand the complex relationship between cannabis and mental health.

Dr. Sultan, reflecting on his clinical experience, noted that he is observing a growing number of teens presenting with new or worsening mental health symptoms linked to cannabis use. He emphasized that mental health disorders are multifaceted, influenced by genetics, environment, and lifestyle, but warned that continued cannabis use could exacerbate symptoms and hinder recovery. He described psychosis and severe mood disorders as “neurotoxic to your brain,” potentially leading to a more rapid deterioration of brain health.

Frequently Asked Questions

What mental health conditions were linked to cannabis use in the study?

The study found that cannabis use was associated with an increased risk of being diagnosed with bipolar disorder, psychotic disorders (such as schizophrenia), anxiety, and depression.

How was the study designed to determine if cannabis use caused mental health problems?

Researchers excluded teenagers who already had symptoms of mental illness before using cannabis, and then followed the participants to see if cannabis use predicted the development of these conditions later in life.

Did the age at which teens started using cannabis affect the results?

Yes, the link between cannabis use and depression and anxiety was weaker for teens who started using cannabis at an older age, suggesting that the developing brain is particularly vulnerable to the effects of the drug.

Given these findings, what steps might individuals and communities take to address the potential risks associated with adolescent cannabis use?