However, the authors point out that further research is needed before the findings can be clinically significant.
Previous research has shown a link between smoking cannabis and psychosis. There is also emerging data that cannabis exposure during adolescence may increase the risk of developing schizophrenia. Predicting who is at risk of developing cannabis psychosis could therefore be used to advise people who smoke cannabis.
Researchers, led by Dr Marta Di Forti at King’s Institute of Psychiatry, studied the AKT1 gene, which is involved in dopamine signaling and known to be abnormal in psychosis. They studied 489 patients with their first episode of psychosis and 278 healthy controls.
They performed genetic tests on all volunteers, and assessed their use of cannabis. They found that cannabis users who carry a particular variant in the AKT1 gene had a two-fold increased probability of a psychotic disorder and this increased up to seven-fold if they used cannabis daily.
Dr Di Forti says: “We found that cannabis users who carry a particular variant in the AKT1 gene had a two-fold increased probability of a psychotic disorder and this increased up to seven-fold if they used cannabis daily. Although using cannabis increases the risk of schizophrenia, most cannabis users come to no harm. It has therefore been suggested that those who develop psychosis may carry some genetic vulnerability.
“Our findings help to explain why one cannabis user develops psychosis while his friends continue smoking without problems. Such findings could also help to design health educational campaigns tailored to reach those young people at particular risk.”
Dr. John Krystal, Editor of Biological Psychiatry says: “While the AKT1 genotype does not rise to the level of a clinically useful test of the risk for cannabis psychosis, it does show that this source of psychosis risk has a genetic underpinning.
“This advance also points to cellular signaling mechanisms mediated by Akt1 as being relevant to the biology of cannabis psychosis. This may suggest research directions for novel therapeutics for cannabis psychosis.”
Full paper: Di Forti, M. et al. “Confirmation that the AKT1 (rs2494732) Genotype Influences the Risk of Psychosis in Cannabis Users” Biological Psychiatry, Volume 72, Issue 10 (November 15, 2012) doi: 10.1016/j.biopsych.2012.06.020
For further information, please contact Seil Collins, Press Officer, King’s College London’s Institute of Psychiatry, at +44 0207 848 5377 or firstname.lastname@example.org.