Evidence suggests that glial dysfunction may be a mechanism contributing to liability for a major depressive disorder.23-25 Prior work on post-mortem brain tissue from participants with depression has reported decreased numbers, density and protein expression of glial cells in the hippocampus and cortico-limbic regions.24 Hviid et al. 23 previously reported that depressed patients had ∼17% lower GFAP serum concentrations at baseline compared with healthy controls. Here, GFAP is linked to major depressive disorder.