IFNB1 and major depressive disorder: On the other hand, microglia from GFAP-IFN mice were hypertrophied, had longer processes and were hyper-ramified, comparable to microglia in the brain of mice reported during aging [106, 107], chronic stress [108, 109], IFN-α-induced depression [110] and following chronic, CNS-targeted production of IFN-β [107].