Objective  To compare differences of neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), complete blood count and brain-derived neurotrophic factor (BDNF) between patients with schizophrenia and those with bipolar disorder.

  Methods  A total of 80 patients with schizophrenia and 70 manic patients with bipolar disorder were enrolled in this study, and were included in schizophrenia group and bipolar disorder group, respectively. At the same time, 77 healthy volunteers were selected as control group. BDNF levels and complete blood cell count were measured in the three groups. The number of white blood cell, neutrophil, lymphocyte, platelet and monocyte was recorded, and NLR, PLR and MLR were calculated.

  Results  Compared with the control group, the PLR and MLR levels of the bipolar disorder group were significantly higher, while the levels of lymphocytes and BDNF were significantly lower (P < 0.05). The levels of white blood cells, monocytes, NLR, MLR and PLR in the schizophrenia group increased, while the levels of BDNF and lymphocytes decreased (P < 0.05). The level of lymphocytes in the schizophrenia group was lower than those in the bipolar disorder group, and the levels of monocytes, NLR, PLR and MLR were higher than those in the bipolar disorder group (P < 0.05), but there was no significant difference in BDNF level between the two groups (P>0.05). There was a significant negative correlation between BDNF and neutrophils in patients with schizophrenia (r=-0.223, P=0.047).

  Conclusion  Patients with schizophrenia and bipolar disorder have inflammation and neurotrophic deficits, and the abnormal levels of hematological inflammatory markers and BDNF are more obvious in patients with schizophrenia. BDNF is significantly correlated with neutrophils in patients with schizophrenia.