Can BDNF and IL-2 be indicators for the diagnosis in schizophrenic patients with depressive symptoms?

The aim of the current study is to determine whether serum levels of brain-derived neurotrophic factor (BDNF) and interleukin-2 (IL-2) can be biological indicators for the diagnosis of schizophrenia in patients with depressive symptoms.

Forty-seven patients (11 patients diagnosed with schizophrenia, 16 patients diagnosed with schizophrenia and comorbid depression and 20 patients diagnosed with major depressive disorder) and 20 healthy subjects were enrolled. The Positive and Negative Symptoms Scale, the Calgary Depression Scale for Schizophrenia and the Hamilton Depression Rating Scale were used for assessment. The serum BDNF and IL-2 levels of all the subjects were studied.

Decreased levels of serum BDNF and increased levels of serum IL-2 were found in the patients diagnosed with either schizophrenia, schizophrenia with depression, or major depressive disorder (p = 0.049, p = 0.010; p = 0.001 and p = 0.044; p = 0.027, p = 0.003; respectively) compared with control group. There were no significant differences between the patient groups in their serum BDNF and IL-2 levels.

The present study suggests that neurotrophic factors and immune system changes are involved in the pathogenesis of schizophrenia with or without depressive symptomatology. However, the data do not clarify whether depressive symptoms in schizophrenia occur as a dimension of schizophrenia or as symptoms of major depression that is comorbid with schizophrenia.