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Cannabis use and risk of psychosis: an etiological link?*

  • Helene Verdoux (a1) and Marie Tournier (a1)


Objective – The nature of the link between cannabis use and psychosis remains to be clarified. Method – The paper reviews the evidence suggesting that cannabis may be a risk factor for psychosis onset. Results – Cross-sectional and retro- spective epidemiological studies show that individuals with psychosis use cannabis more often than other individuals in the gener- al population. It has long been considered that this association is explained by the self-medication hypothesis, postulating that cannabis is used to self-medicate psychotic symptoms. This hypothesis has been recently challenged by several prospective stud- ies carried out in population-based samples, showing that cannabis exposure is associated with an increased risk of psychosis, pos- sibly by interacting with a pre-existing vulnerability for these disorders. A dose-response relationship was found between cannabis exposure and risk of psychosis, and this association was independent from potential confounding factors such as exposure to other drugs and pre-existence of psychotic symptoms. However, the diagnostic specificity is weak, as cannabis exposure may be a risk factor for the occurrence of a large spectrum of psychiatric disorders, ranging from schizophrenia to mood and anxiety disorders. Conclusion – Considering the growing number of adolescents exposed to cannabis, the impact of this substance on the population mental health should be further explored.


Corresponding author

Address for correspondence: Prof. H.Verdoux, Hôpital Charles Perrens, 121 rue de la Béchade, 33076 Bordeaux Cedex (France). Fax: (33) 556-56-35-46 E-mail:


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Paper presented at the VI National Congress of the Italian Society of Psychiatric Epidemiology (SIEP), held in Sirmione (BS), 6-8 November 2003.



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