However, we did not find a significant correlation between BDNF levels and the severity of positive or negative symptoms, which were in agreement with some previous studies (17), suggesting that low BDNF levels may have a small and insignificant relationship with the psychopathology of schizophrenia, or it may be just a pathological epiphenomenon of schizophrenia. This evidence concerns the gene BDNF and schizophrenia.