What the researchers compared
Di Forti and colleagues studied 489 people with first-episode psychosis and 278 controls. Among daily cannabis users, the C/C group at AKT1 rs2494732 had higher odds of psychosis than the T/T group: an odds ratio of 7.23, with a wide 95% confidence interval of 1.37–38.12. Original study.
What the number means
That comparison is between genotype groups among daily users. It is not a sevenfold estimate for every cannabis user, an absolute probability of developing psychosis, or a diagnostic test. The case-control design and wide interval warrant caution. The study cannot establish that a different genotype makes cannabis safe for an individual.
Read the original research
Confirmation that the AKT1 (rs2494732) genotype influences the risk of psychosis in cannabis users.
Biological psychiatry
Citation
Marta Di Forti; Conrad Iyegbe; Hannah Sallis; Anna Kolliakou; M Aurora Falcone; Alessandra Paparelli; Miriam Sirianni; Caterina La Cascia; Simona A Stilo; Tiago Reis Marques; Rowena Handley; Valeria Mondelli; Paola Dazzan; Carmine Pariante; Anthony S David; Craig Morgan; John Powell; Robin M Murray. (2012). Confirmation that the AKT1 (rs2494732) genotype influences the risk of psychosis in cannabis users.. Biological psychiatry. https://doi.org/10.1016/j.biopsych.2012.06.020