We observed that FEP had higher serum C3 and C4 protein levels than HC, suggesting that aberrant expression of complement proteins may be potential biomarkers for schizophrenia; C4 polymorphism affected serum C4 protein levels in FEP but not in HC, suggesting that genotype may be considered as an important risk factor for the development of schizophrenia. This evidence concerns the gene VTN and schizophrenia.