Pro-inflammatory cytokines and cognitive dysfunction among patients with bipolar disorder and major depression

Bipolar disorder and major depressive disorder (MDD) have been demonstrated to be associated with proinflammatory states and cognitive function deficits. We aimed to investigate the differences of cognitive function and proinflammatory cytokines between patients with bipolar I disorder (BDI), bipolar II disorder (BDII), and MDD.

Thirty-seven patients with BDI, 33 with BDII, 25 with MDD, and 54 age-, sex-matched controls were enrolled. All patients had a clinical global impression-severity scale ≤2. Serum levels of proinflammatory markers, including soluble interleukin-6 receptor, C-reactive protein, and soluble tumor necrosis factor receptor 1 (sTNF-αR1) were measured. Performance in the Word List Memory Task (WLMT), Wisconsin Card Sorting Task (WCST), 2-back task, Go/No-Go task, and divided attention task was assessed.

Patients with BDI had higher levels of sTNF-αR1 than patients with MDD and controls (P < 0.001). Patients with BDI performed worse on WLMT, WCST, 2-back task, divided attention_visual and divided attention_auditory tasks than the other three groups (all P < 0.05). Furthermore, sTNF-αR1 levels were negatively correlated with cognitive function measured using the WLMT and divided attention_auditory (all P < 0.05).

Patients with BDI had higher levels of sTNF-αR1 and cognitive function impairments than the remaining groups. Future studies are needed to explore the pathophysiology of sTNF-αR1 in the contribution of cognitive alterations.