Absence of an association between serum interleukin-6 and brain-derived neurotrophic factor in drug-naïve first-episode major depression

ABSTRACT Peripheral and central cytokine interleukin-6 (IL-6) levels play an important role in the pathophysiology of major depression (MD). We investigated the association between serum levels of IL-6 and brain-derived neurotrophic factor (BDNF) in drug-naïve, first-episode patients with MD. This study included 28 patients (male/female: 11/17; mean [standard deviation] age, 46.7 [11.9] years) who met the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria for MD without any physical diseases. We evaluated the severity of depression using the Hamilton Rating Scale for Depression. No associations were found between serum levels of IL-6 and BDNF (r=-0.102, P =0.605). These results suggest that IL-6 does not influence BDNF and vice versa, but both act in a peripheral manner.