Decreased levels of serum brain-derived neurotrophic factor in drug-naive first-episode schizophrenia: relationship to clinical phenotypes

There is accumulating evidence that brain-derived neurotrophic factor (BDNF) may be involved in the pathophysiology of patients with schizophrenia. Clinical studies show reductions in BDNF in schizophrenic patients treated with first generation antipsychotics or second generation antipsychotics. However, there have been few systematic studies to examine the relationship between BDNF levels and psychopathology in first-episode and drug-na < ve patients with schizophrenia. Serum BDNF levels were determined using enzyme-linked-immunosorbent assay (ELISA) in the serum of 88 never-medicated first-episode and 90 healthy controls subjects matched for age and gender. The schizophrenia symptomatology and the depressive symptoms were assessed by the positive and negative syndrome scale (PANSS) and the Hamilton rating (HAMD) scale for depression. The results showed that BDNF levels were significantly lower in first-episode patients with schizophrenia than in healthy control subjects (9.0 +/- 4.2 ng/ml vs 12.1 +/- 2.2 ng/ml; F = 37.6; df = 1, 176; p < 0.0001). A significant positive correlation between BDNF levels and PANSS positive subscore was observed (r = 0.29; df = 88; p = 0.008). Furthermore, higher BDNF levels were observed in patients with paranoid subtype of schizophrenia. However, no significant correlation between BDNF and HAMD total score was found. Low BDNF levels at the onset of psychosis suggest that it may contribute to the pathogenesis of schizophrenia and perhaps, could be a candidate biological marker for positive symptoms.