Daily cannabis use is proven to cause psychosis in young people

This comprehensive review examined the relationship between daily cannabis use and mental health disorders by analyzing evidence from multiple research approaches—epidemiological studies, genetic research, experiments, and preclinical work. The research focused on adolescents and young adults (ages 15-25) who engage in daily cannabis use or develop cannabis use disorder, comparing this group with peers who don't use cannabis regularly. The key finding is that credible evidence demonstrates daily cannabis use is a direct cause of psychosis, meaning regular cannabis users have a significantly elevated risk of developing psychotic symptoms or disorders.

For other mental health conditions, the evidence was more complex and less conclusive. While cannabis use correlates with bipolar disorder, depression, and anxiety, the direction of causality remains unclear—users might be self-medicating existing anxiety or depression, the conditions and cannabis use might share common underlying risk factors, or the relationship might work both ways. The review also found associations with increased suicidal behaviors, though this link requires further investigation. Notably, there were fewer high-quality studies examining cannabis's relationship with bipolar disorder specifically.

The research highlights a critical public health challenge: young people with mental health conditions are more vulnerable to developing cannabis use disorders, creating a potentially harmful cycle. The authors emphasize that effective interventions for cannabis use disorder in people already experiencing mental illness should be a priority. This is particularly important given that cannabis use typically begins during the developmental window when anxiety, depression, and psychosis naturally emerge, making it difficult to disentangle cause from effect.