Clinical studies have found that compared with normal people, patients with depression have proinflammatory cytokines such as tumor necrosis factor-α(TNF-α)、Interleukin-1β(IL-1β)、IL-6 and interferon While anti-inflammatory cytokines such as IL-10, IL-4, IL-8 and transforming growth factor. This evidence concerns the gene IL4 and major depressive disorder.