Day-of-injury GFAP values were significantly (p < 0.0001) lower in participants with (median: 142.9 [IQR: 21.0–529.3] pg/ml) versus those without (median: 314.0 [IQR: 84.6–924.3] pg/ml) probable PTSD at the 6-month assessment (Fig. 2a). This evidence concerns the gene GFAP and post-traumatic stress disorder.