NGF and schizophrenia: Significant associations were observed between chronic schizophrenia and reduced levels of NGF-β (B = 1.040, P < 0.001, RR = 2.829, 95% CI: 2.101−3.811) and BDNF (B = 0.526, P = 0.001, RR = 1.692, 95% CI: 1.241−2.306).