Although increased expression of GFAP is commonly observed in reactive astrogliosis, postmortem results suggest that the frequency and intensity of reactive astrogliosis are decreased in the brains of patients with MDD.166 Accompanied by a decreased astrocyte density, the levels of GFAP and the GFAP intermediate filament domain are also reduced in brain samples from patients with MDD.167 Researchers have even proposed that the GFAP content in serum can be used to determine the severity of MDD,168 but this point is controversial. Here, GFAP is linked to major depressive disorder.