Epidemiologic research suggests that cannabis use may be a significant risk factor for psychotic disorders. A meta-analysis of longitudinal studies estimated that lifetime cannabis users had an odds ratio of 2.58 (95% CI 1.08–6.13) for psychotic disorders compared to non-users (Moore et al., Reference Moore, Zammit, Lingford-Hughes, Barnes, Jones, Burke and Lewis2007). Another meta-analysis found an odds ratio of 3.90 (95% CI 2.84–5.34) for psychotic disorders among the most frequent cannabis users compared to non-users, suggesting dose–response (Marconi, Di Forti, Lewis, Murray, & Vassos, Reference Marconi, Di Forti, Lewis, Murray and Vassos2016). Whether cannabis use is causally related to psychotic disorders continues to be debated, with recent genetic studies raising uncertainty about the directionality of the relationship and the magnitude of association (Ganesh & D’Souza, Reference Ganesh and D’Souza2022; Gillespie & Kendler, Reference Gillespie and Kendler2021).

This study provides new evidence of a strong but age-dependent association between cannabis use and risk of psychotic disorder, consistent with the neurodevelopmental theory that adolescence is a vulnerable time to use cannabis. The strength of association during adolescence was notably greater than in previous studies, possibly reflecting the recent rise in cannabis potency. Age-dependent association of cannabis use with risk of psychotic disorder Psychological Medicine , First View , pp. 1 – 11 https://doi.org/10.1017/S0033291724000990