GFAP and major depressive disorder: Adjusting for age, sex, psychiatric history and prior TBI, we found a significant interaction effect between GFAP levels and CT status, indicating an inverse association of GFAP levels with depression in the first year post-injury among CT-subjects (adjusted odds ratios = 0.84, 95% CI: 0.77–0.92 per log unit increase; see Table 4).