Objective  To calculate the neutrophil-to-lymphocyte ratio (NLR) and the platelet-to-lymphocyte ratio (PLR), detect the concentration of glial cell line-derived neurotrophic factor (GDNF), and investigate their effects on cognitive function in patients with bipolar disorders.

  Methods  A total of 55 patients with bipolar disorders and 54 healthy controls were selected as research objects, and their NLR, PLR and GDNF were measured. Cognitive function of the patients was evaluated by verbal fluency test (VFT), trail-making test (TMT) and Stroop test.

  Results  The NLR and PLR of the observation group were significantly higher than those of the control group, while the GDNF was significantly lower (P < 0.01). In the observation group, NLR and GDNF were correlated with VFT-action (r=-0.379, P=0.004; r=0.269, P=0.047) and TMT-B (r=0.597, P < 0.001; r=-0.407, P=0.002). NLR was significantly negatively correlated with GDNF (r=-0.415, P=0.002). After adjusting for confounding factors by hierarchical regression, NLR (β=15.475, P < 0.001) and GDNF (β=-0.016, P=0.046) were able to predict performance of TMT-B, in which interactive items of NLR and GDNF (β=0.166, P < 0.001) were able to positively predict cognitive function (R²=0.914), and the result indicated that the interaction between the two indexes can explain 30.5% of the total variation of TMT-B in cognitive function.

  Conclusion  Inflammation factors, neurotrophic factor and their interactions are closely related to cognitive function. A larger sample size prospective study is needed in the future to explore the effects of inflammation factors and GDNF on cognitive function.