This study designed to investigate the pathogenic mechanisms of schizophrenia by the assessment the hypothalamic–pituitary–adrenal axis and their association with pro-inflammatory cytokines and identify any association between the single nucleotide polymorphism of the D- amino-acid oxidase activator and Methylenetetrahydrofolate reductase genes and schizophrenia with assessment the frequency of Human Leukocyte Antigen (HLA) class 1 (A&B) alleles in schizophrenic patients.