Associations between polymorphisms in CYP1A2 and ABCB1 sequences and treatment responses or weight gain have been previously reported [14, 15], and it is presumed that genetic polymorphisms that affect the serum concentration of olanzapine could be associated with ANS activity in olanzapine-treated patients with schizophrenia. This evidence concerns the gene ABCB1 and schizophrenia.