The present study is the first, to the best of our knowledge, to analyze the association of polymorphisms in CYP1A2, UGT1A4, and ABCB1―namely rs2069514, rs762551, rs2011425, rs1045642, rs1128503, rs2032582, and rs2235048―with ANS dysfunction and other side effects in schizophrenia patients treated with the atypical antipsychotic olanzapine. The gene discussed is CYP1A2; the disease is schizophrenia.