Cannabis use during adolescence was associated with an 11-fold psychosis risk, but no significant risk during young adulthood, suggesting a critical vulnerability window.
Parents, adolescent health providers, mental health clinicians, and policymakers.
Adolescent cannabis users: 11x psychosis risk; young adults: no significant increase
What the researchers found
Among 11,363 Ontario youth, cannabis use was associated with 11.2-fold increased psychosis risk during adolescence (12-19) but only non-significant 1.3-fold during young adulthood (20-33). Restricting to hospitalizations/ER: 26.7-fold risk in adolescents.
Why it matters
One of the strongest demonstrations of age-dependent psychosis risk, using population data and healthcare records. The dramatically higher adolescent risk has direct prevention implications.
The numbers in context
N=11,363. Adolescence: aHR=11.2 (CI 4.6-27.3). Young adulthood: aHR=1.3 (CI 0.6-2.6). Hospitalizations only: adolescence aHR=26.7 (CI 7.7-92.8).
How the study worked
Population-based cohort linking 2009-2012 survey data with Ontario universal healthcare records through 2018. N=11,363 aged 12-24 with no prior psychotic disorder.
What this study cannot tell us
Observational. Single baseline cannabis measure. Possible confounding. Wide confidence intervals for hospitalization analysis.
How to read the evidence
Large population-based cohort with universal healthcare outcome data, though observational.
When this study was published
Published in 2024 with 2009-2012 baseline followed through 2018.
The bigger picture
The stronger associations compared to older studies may reflect increasing cannabis potency, providing modern, high-potency-era evidence for the neurodevelopmental theory.
Questions still open
- Does increasing potency explain stronger associations than older research?
- Is there a specific age threshold below which psychosis risk jumps?
Common questions
Does cannabis cause psychosis in teenagers?
Is cannabis safer for adults than teenagers?
Read the original research
Age-dependent association of cannabis use with risk of psychotic disorder.
Psychological medicine, 54(11), 2926-2936
Citation
McDonald, André J; Kurdyak, Paul; Rehm, Jürgen; Roerecke, Michael; Bondy, Susan J. (2024). Age-dependent association of cannabis use with risk of psychotic disorder.. Psychological medicine, 54(11), 2926-2936. https://doi.org/10.1017/S0033291724000990
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