IL6 and major depressive disorder: Depression leads to an increase in proinflammatory cytokines, tumor necrosis factor-alpha (TNF-α), interleukin-1 (IL-1), and interleukin-6 (IL-6) which stimulate central serotonin neurotransmission and are linked to hypothalamic-pituitary-adrenal overactivity increasing the risk of CVD and MI.