Reduced Serum BDNF Levels in Schizophrenia Patients on Clozapine or Typical Antipsychotics

Neurotrophic factors regulate neuronal development & synaptic plasticity, possibly playing a role in the pathophysiology of schizophrenia & other psychiatric disorders. Decreased brain-derived neurotrophic factor (BDNF) levels have been found in brains & in the serum of schizophrenic patients, but results are inconsistent. Also, clozapine may upregulate brain BDNF expression. In the present study, we assessed serum BDNF immunoreactivity in 44 schizophrenic patients (20 on clozapine & 24 on typical antipsychotics) & in 25 healthy volunteers. Serum BDNF levels were measured using an enzyme immunoassay. Healthy controls showed significantly higher levels of BDNF compared to the whole group of schizophrenic patients (p < 0.001) as well as to the subgroups on typical antipsychotics & clozapine (p < 0.001). Serum BDNF values for controls were 168.8 - 26.3 pg/ml, for the clozapine group were 125.4 - 44.5 pg/ml & for the group on typicals were 101.3 - 51.6 pg/ml. BDNF values from patients on clozapine were non-significantly higher than values from patients on typical antipsychotics (p = 0.09). Serum BDNF was strongly & positively correlated with clozapine dose (r = 0.643; p = 0.002) but not with other demographic characteristics. These results reinforce previous findings of reduced serum BDNF levels in schizophrenic patients & suggest a differential effect of clozapine compared to typical antipsychotics on such levels. Tables, Figures, References. [Copyright 2006 Elsevier Ltd.]