Gene-environment interplay between cannabis and psychosis.

Cannabis use is considered a contributory cause of schizophrenia and psychotic illness, but only a small proportion of users develop psychosis. The amount, duration, and strength of cannabis consumption, as well as age at first exposure, partly explain this. Genetic factors likely play a role in both short- and long-term effects on psychosis. This review discusses studies using genetic, epidemiological, experimental, and observational techniques to investigate gene-environment correlation and interaction within the cannabis-psychosis association. Evidence suggests that mechanisms of gene-environment interaction underlie the link, with multiple genetic variations and other environmental factors (e.g., stress) interacting with cannabis to increase psychosis risk. Further research on higher-order interactions is needed.

Study at a glance

Abstract

Cannabis use is considered a contributory cause of schizophrenia and psychotic illness. However, only a small proportion of cannabis users develop psychosis. This can partly be explained by the amount and duration of the consumption of cannabis and by its strength but also by the age at which individuals are first exposed to cannabis. Genetic factors, in particular, are likely to play a role in the short- and the long-term effects cannabis may have on psychosis outcome. This review will therefore consider the interplay between genes and exposure to cannabis in the development of psychotic symptoms and schizophrenia. Studies using genetic, epidemiological, experimental, and observational techniques will be discussed to investigate gene-environment correlation gene-environment interaction, and higher order interactions within the cannabis-psychosis association. Evidence suggests that mechanisms of gene-environment interaction are likely to underlie the association between cannabis and psychosis. In this respect, multiple variations within multiple genes--rather than single genetic polymorphisms--together with other environmental factors (eg, stress) may interact with cannabis to increase the risk of psychosis. Further research on these higher order interactions is needed to better understand the biological pathway by which cannabis use, in some individuals, may cause psychosis in the short- and long term.