The ability of teens, and, in the case of younger athletes, their parents, to accurately recall the severity of symptoms experienced before after a mild traumatic brain injury (mTBI) injury is subject to a "good old days" bias and declines dramatically over time, says a new study, which suggests that using symptom ratings of pre-injury functioning obtained as soon as possible after injury might result in a 5 to 7-fold improvement in a clinician's identification of patients who have clinically recovered from concussion.