Proinflammatory cytokines such as interferon gamma (IFNγ), tumor necrosis factor-alpha (TNFα), interleukin 1 beta (IL-1β), and interleukin 6 (IL-6) can reach the brain parenchyma and play a role in the development of depressive disorder through regulating synaptic transmission, neuronal excitability, neuronal survival, and synaptic plasticity [46]. This evidence concerns the gene IL6 and depressive disorder.