IL6 and mood disorder: Furthermore, in the last two decades, increased blood and cerebrospinal fluid (CSF) pro-inflammatory cytokine concentrations, including interleukin-1β (IL-1β), IL-6, interferon-γ (IFN-γ), and tumor necrosis factor alpha (TNF-α) were revealed in MDD and BDs [35,47,48,49,50,51], leading to the cytokines hypothesis of mood disorders [39] (Figure 2).