GDNF and schizophrenia: CSF APP and GDNF levels were significantly lower in patients with schizophrenia {p = 0.019 (corrected p = 0.11) and 0.035 (corrected p = 0.21)}, while CSF APP and NCAM-1 levels were significantly lower in patients with BD {p = 0.002 (corrected p = 0.011) and 0.017 (corrected p = 0.097)}, than in healthy controls (Fig. 1).