CYP2D6 and autism spectrum disorder: Furthermore, our investigation of different alleles agree with the results of previous studies [12, 23], as well as a recent study involving children and adolescents with autism spectrum disorders which reported plasma concentrations of risperidone and RIS/9-OH-RIS to be significantly associated with CYP2D6*10, while plasma concentration of 9-OH-RIS was not found to be significantly correlated [13].