Cannabis and mental health in adolescents: changes in associations over 15 years.

Purpose: Recent changes in the cannabis market, including decreased adolescence usage, increased Δ9-tetrahydrocannabinol levels and rising mental disorders over the last decade raises questions about the changing profile of cannabis consumers.

Methods: This study explores the trends of associations between regular cannabis use and mental health in five waves of a national representative survey of 17-year-old French adolescents, including more than 150,000 participants. Multivariable models, adjusted for gender and socioeconomic variables, were used.

Results: Cannabis use and mental health indicators showed some variations over time, with increasing divergence between 2017 and 2022. Regular use of cannabis decreased from 7.4% in 2008 to 3.8% in 2022 (p < 0.001). In contrast, suicidal ideation in the past year increased from 16% in 2008 to 18% in 2022 (p = 0.009), although it followed a U-shaped trend. The association between regular cannabis use and suicidal ideation in the past year increased from 1.44 (CI: 1.29-1.61) in 2008 to 2.52 (CI: 2.05-3.10) in 2022. Similarly, the association between cannabis use and antidepressant use in the past year increased from 2.57 (CI: 2.18-3.03) in 2008 to 4.47 (CI: 3.35-5.97) in 2022.

Conclusion: These results suggest that cannabis users are now more prone to mental health disorders compared to 15 years ago. Several mechanisms might explain these findings, including the self-selection of a population with both vulnerabilities, changes in the effects of cannabis, or the use of cannabis as a self-medication strategy.