Recovery from mild traumatic brain injury (mTBI) is primarily based on the resolution of post-concussive symptoms back to a premorbid level. However, the "good old days" bias means fewer premorbid symptoms are retrospectively recalled, thus skewing the determination of recovery relative to pre-injury. The objectives of this study were to investigate the "good old days" bias in pediatric mTBI and demonstrate the implications of this bias on perceived recovery. Children and adolescents 2-18 years old (mean = 10.9, SD = 4.4, N = 412) were recruited after sustaining an mTBI. Ratings of premorbid symptoms were provided: (a) in the Emergency Department (ED; by parents), (b) retrospectively at a 1-month follow-up (by parents and adolescents), and (c) retrospectively at a 3-month follow-up (by parents and adolescents). Parent ratings of premorbid symptoms decreased by 80% from the ED to 1-month post-injury (p < .001) but were stable from 1 to 3 months post-injury (p < .05). Adolescents premorbid ratings declined from 1 to 3 months post-injury. Slow recovery did not have a differential impact on premorbid reporting. Using premorbid ratings obtained in the ED, instead of retrospective symptom reporting at the time of follow-up, suggests that a significant minority of patients believed to be "not recovered" actually have the "same or lower" symptom ratings at 1 (29%) and 3 months (41%) post-injury compared with before the injury. The "good old days" bias is present in pediatric mTBI by 1-month post-injury, influences retrospective symptom reporting, and has measureable implications for determining recovery in research and clinical practice.
Keywords: Bias; Children; Concussion; Post-concussion syndrome; Recovery; Symptom.