The Differential Levels of Inflammatory Cytokines and BDNF among Bipolar Spectrum Disorders

Objective: Emerging evidence suggests that inflammation and neurodegeneration underlies bipolar disorder. To investigate biological markers of cytokines and brain-derived neurotrophic factor between bipolar I, bipolar II, and other specified bipolar disorder with short duration hypomania may support the association with inflammatory dysregulation and bipolar disorder and, more specifically, provide evidence for other specified bipolar disorder with short duration hypomania patients were similar to bipolar II disorder patients from a biological marker perspective. Methods: We enrolled patients with bipolar I disorder (n=234), bipolar II disorder (n=260), other specified bipolar disorder with short duration hypomania (n=243), and healthy controls (n=140). Their clinical symptoms were rated using the Hamilton Depression Rating Scale and Young Mania Rating Scale. Inflammatory cytokine (tumor necrosis factor-α, C-reactive protein, transforming growth factor-β1, and interleukin-8) and brain-derived neurotrophic factor levels were measured in each group. Multivariate analysis of covariance and linear regression controlled for possible confounders were used to compare cytokine and brain-derived neurotrophic factor levels among the groups. Results: Multivariate analysis of covariance adjusted for age and sex and a main effect of diagnosis was significant ( P