Longitudinal Associations Between ADHD Symptoms and Cannabis Use in Adolescence: Exploration of the Dynamic Cross-Lagged Effects

Introduction Adolescence represents a period of heightened vulnerability for the initiation of psychoactive substance use, such as cannabis. A growing body of research suggests a marked co-occurrence between attention-deficit/hyperactivity disorder (ADHD) symptoms and early or problematic cannabis use. However, most of these studies are cross-sectional, raising questions about the nature and directionality of this association. Understanding the underlying dynamics of this relationship is of particular importance for both prevention and intervention among at-risk adolescents. Method Data were drawn from CoVenture , a longitudinal study of 3,756 secondary school students from the Greater Montreal area. Each year from Grade 7 to Grade 11, participants self-reported their frequency of alcohol and cannabis use, as well as ADHD symptoms. A Random Intercept Cross-Lagged Panel Model was used to assess within-person associations over time, controlling for alcohol use and demographic covariates. Results At a between-person level, cannabis use and ADHD symptoms were significantly associated, even after controlling for alcohol use. At a within-person level, findings suggest a bidirectional relationship, starting in Grade 8. Greater ADHD symptom severity significantly predicted subsequent year increases in cannabis use. The reverse pathway—from greater cannabis use to subsequent year increases in ADHD symptoms—was also significant. Further analysis showed that higher cannabis use in Grade 9 increased the risk of reaching a clinically relevant level of ADHD symptoms in Grade 10. Conclusion The findings suggest that ADHD and cannabis use are related through a common vulnerability mutually exacerbating relationship where (a) ADHD symptoms present a risk factor for cannabis use onset, and (b) once cannabis use has begun, cannabis use and ADHD symptoms appear to mutually predict each other, suggesting a potential “spiral effect” that warrants attention.