IL6 and major depressive disorder: Within the central nervous system (CNS), IL-6 is synthesized by an array of cells including neurons, astrocytes, microglial cells, and endothelial cells, playing a vital role in the inflammatory response linked to PSD Elevated serum IL-6 levels in the acute phase of ischemic stroke are independently associated with the occurrence of depression at two weeks and one-year post-stroke[29].