Chronic inflammatory processes in the brain associated with excessive activation of microglia and increased production of pro-inflammatory cytokines are one of the key factors leading to the development of depressive symptoms, as patients suffering from this mental illness are very often characterized by elevated levels of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), interleukin-1 beta (IL-1β), C-reactive protein (CRP), and interferon-gamma (IFN-γ) in the cerebrospinal fluid and the blood [59–61]. Here, IFNG is linked to psychiatric disorder.