IL6 and major depressive disorder: IL6 has been identified as one of the central cytokines associated with depression (29, 30); it is also known that one of the main functions of IL6 is to promote the secretion of proinflammatory cytokines leading to systemic inflammation, in addition within the peripheral and Central Nervous System (CNS), IL-6 can act as a neuronal growth factor inducing neurite development and nerve regeneration (31–33).