GFAP and attention deficit-hyperactivity disorder: Furthermore, ADHD has recently been suggested to increase vulnerability to subconcussive head impacts, as exhibited by acute declines in cognitive performance and increases in blood biomarker levels associated with neuronal injury (ubiquitin-C-terminal-hydrolase-L1; UCH-L1) and astrocyte activation (glial-fibrillary-acidic-protein; GFAP) following 10 acute soccer headers (8).