We evaluated two antioxidant enzymes that are members of the GST family, which are known to have a deletion polymorphism, GSTM1 and GSTT1, in TRS patients from Brazil diagnosed according to American Psychiatric Association criteria [22], to achieve a better understanding of the contribution of these genes to the development of schizophrenia and its refractory manifestation. Here, GSTM1 is linked to schizophrenia.