As mentioned in the previous section, pro‐inflammatory cytokines, such as IL‐1β, TNF‐α, IFN‐γ and TGF‐β, can cross the BBB and initiate or modulate astrogliosis, suggesting that stress‐induced exacerbated activation of these glial cells may contribute to depression pathogenesis (see Figure 2). Here, IFNG is linked to major depressive disorder.