IL6 and concussion: However, not all studies have found success with IL-6 as an RHI-related biomarker.Parkin et al conducted an immunoassay of blood-based immune markers up to 3 monthsafter pediatric concussion, observing that patients with normal recovery exhibitedthe same gradual decrease in IL-6 expression as patients with persisting symptomsshowing concentration difficulty as well as cognitive and behavioral deficits (73).