Influencedbythe"GoodOldDays"Bias:TangibleImplicationsforClinical Practice and Outcomes Research †

Recoveryfrommildtraumaticbraininjury(mTBI)isprimarilybasedontheresolutionofpost-concussivesymptomsbacktoapremorbidlevel. However, the “good old days” bias means fewer premorbid symptoms are retrospectively recalled, thus skewing the determination of recovery relativetopre-injury.Theobjectivesofthisstudyweretoinvestigatethe“goodolddays”biasinpediatricmTBIanddemonstratetheimplications ofthisbiasonperceivedrecovery.Childrenandadolescents2‐18yearsold(mean ¼ 10.9,SD ¼ 4.4,N ¼ 412)wererecruitedaftersustainingan mTBI. Ratings of premorbid symptoms were provided: (a) in the Emergency Department (ED; by parents), (b) retrospectively at a 1-month follow-up(byparentsandadolescents),and(c)retrospectivelyata3-monthfollow-up(byparentsandadolescents).Parentratingsofpremorbid 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). Adolescentspremorbidratingsdeclinedfrom1to3monthspost-injury.Slowrecoverydidnothaveadifferentialimpactonpremorbidreporting. 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%) postinjury 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.