While this study isn’t youth-specific (it included individuals age 18-64), the findings are still applicable as they show an association of daily use of high potency cannabis increasing occurrences of first-episode psychosis. If high potency cannabis products were no longer available, the incidence of first-episode psychosis dramatically decreased. Most importantly, it provides the first direct evidence that cannabis use has an effect on variation in the incidence of psychotic disorders.
by Di Forti M et al
Read the full study at the National Library of Medicine (PubMed.gov).