Thus, in this study, we examined the pharmacogenetic interindividual differences in the effects of particular atypical antipsychotics, with an emphasis on the relationship with the activity of P-glycoprotein (P-gp), to clarify the individual differences in ANS activity during atypical antipsychotic―risperidone, olanzapine, quetiapine, and aripiprazole―treatment in schizophrenia. This evidence concerns the gene ABCB1 and schizophrenia.