A previous study involving 136 patients with psychotic disorders treated with a single-dose of risperidone, did not identify any significant association between CYP2D6 polymorphisms and clinical recovery [15], which was supported by another study involving female patients with schizophrenia that found that PANSS improved following risperidone treatment, but was not associated with CYP2D6 genotype [16]. This evidence concerns the gene CYP2D6 and psychotic disorder.