Cannabis use and risk of psychosis: an etiological link?

Abstract

SummaryObjective – 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.