This gene × environment interaction was replicated in a subsequent study of 489 patients with first-episode psychosis where carriers of the C/C genotype with a history of cannabis use were again shown to have greater than twofold risk of developing a psychotic disorder.9 Cognitive impacts of this polymorphism have also been observed with cannabis-using psychotic patients who are carriers of the AKT1 rs2494732 C/C genotype performing more poorly on a task of sustained attention than T/T carriers.10 This evidence concerns the gene AKT1 and psychotic disorder.