Association between increased serum interleukin-8 levels and improved cognition in major depressive patients with SSRIs.

Background: The effect of neuroinflammatory cytokines on cognitive deficits in patients with major depressive disorder (MDD) can be altered by selective serotonin reuptake inhibitors (SSRIs). This study aimed to examine serum interleukin-8 (IL-8) levels, cognitive function, and their associations in MDD patients with SSRIs.

Methods: Thirty SSRI-treated MDD patients and 101 healthy controls were recruited for this study. We examined cognitive performance using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and serum IL-8 levels using the Human Inflammatory Cytokine Cytometric Bead Array in both cases and controls.

Results: The RBANS test scores were significantly lower in MDD patients with SSRIs than in healthy controls after controlling for covariates (all p < 0.001). Serum levels of IL-8 were higher in MDD patients with SSRIs than in healthy controls after adjusting for covariates (F = 3.82, p = 0.05). Serum IL-8 levels were positively correlated with sub-scores of delayed memory (r = 0.37, p = 0.04) and visuospatial/constructional (r = 0.43, p = 0.02) in MDD patients with SSRIs but not in in healthy controls (delayed memory score: r = -0.12, p = 0.24; visuospatial/constructional score: r = 0.02, p = 0.81).

Conclusions: Our findings suggested that increased serum IL-8 level might not only be involved in the MDD psychopathology or the use of SSRIs but also correspond to improving MDD delayed memory and visuospatial/constructional function.