© 2004 The Royal College of Psychiatrists
Correspondence |
Cannabis and psychosis
Service Hospitalo-Universitaire de Santé Mentale et Thérapeutique, Prs H. Lôo et J.-P. Olié, Centre Hospitalier Sainte-Anne, I Rue Cabanis, F-75014 Paris, France
Arseneault et al (2004) very accurately reviewed recent epidemiological data and concluded that cannabis use should now be considered as a component cause leading to psychosis. Yet at least two unanswered questions remain. How can cannabis lead to psychosis? Are some subjects specifically vulnerable to the psychotogenic effect of cannabis?
Several studies, including the Dunedin study, have suggested that adolescents are more vulnerable to cannabis (Arseneault et al, 2004). Interestingly, the effects of cannabis on cognitive function also seem more pronounced in adolescents (Ehrenreich et al, 1999; Pope et al, 2003). This difference might also reflect pre-existing differences in cognitive ability between groups.
Cannabis interferes with endocannabinoid systems, known to be involved in neurodevelopment. In rats, chronic cannabinoid treatment during puberty induces behavioural and cognitive changes that are not found when the treatment is done in adulthood (Schneider & Koch, 2003).
Together, these observations are compatible with the idea that cannabis consumption could alter the last steps of brain maturation, leading to cognitive dysfunction and, in turn, enhancing the risk of psychosis. On the other hand, we recently suggested that genetic variants of the cannabinoid receptor type 1 could be associated with a specific sensitivity to cannabis (Krebs et al, 2002). Further studies are now needed to identify subjects ‘highly sensitive’ to the psychotogenic effect of cannabis, by coupling genetic analysis and cognitive testing to prospective follow-up.
REFERENCES
- Arseneault, L., Cannon, M., Witton, J., et al
(2004) Causal association between cannabis and psychosis:
examination of the evidence. British Journal of
Psychiatry, 184, 110
-117.
[Abstract/Free Full Text] - Ehrenreich, H., Rinn, T., Kunert, H. J., et al (1999) Specific attentional dysfunction in adults following early start of cannabis use. Psychopharmacology, 142, 295 -301.[CrossRef][Medline]
- Krebs, M.-O., Leroy, S., Duaux, E., et al (2002) Vulnerability to cannabis, schizophrenia and the (ATT) N polymorphism of the cannabinoid receptor type 1 (CMRI) gene. Schizophrenia Research, 53 (suppl. 3), 72 .
- Pope, H. G., Gruber, A. J., Hudson, J. I., et al (2003) Early-onset cannabis use and cognitive deficits: what is the nature of the association? Drug and Alcohol Dependence, 69, 303 -310.[CrossRef][Medline]
- Schneider, M. & Koch, M. (2003) Chronic pubertal, but not adult chronic cannabinoid treatment impairs sensorimotor gating, recognition memory, and the performance in a progressive ratio task in adult rats. Neuropsychopharmacology, 28, 1760 -1769.[CrossRef][Medline]
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