Authoritative sources advise clinicians and parents that a history of prior concussion confers increased risk for worse outcome from a future concussion. However, the strength of the evidence supporting such pronouncements and thus the extent to which clinicians should incorporate this information into their care and management of pediatric concussion is unclear. This systematic review critically analyzed and synthesized the literature on the association between a history of prior concussion and prognosis/clinical outcome following a subsequent sport-related concussion among children and adolescents. The online databases PubMed, MEDLINE®, PsycINFO®, CINAHL, Cochrane Library, EMBASE, SPORTDiscus, Scopus, and Web of Science were searched from inception to May 15, 2021. From 5118 total records screened, 51 studies (46 cohort studies and five case-control studies) met inclusion criteria, reporting concussion recovery or outcome for 26,643 youth. A median of 36% had a prior history of concussion. Across all studies and outcomes, the majority (k = 37, 72.5%) did not find a statistically significant association between lifetime history of concussion and outcome from a subsequent concussion. Important methodological limitations in the literature were identified. Available studies do not provide consistent or compelling evidence that children and adolescents with a history of concussion are at increased risk for worse clinical outcome following a subsequent sport-related concussion-although methodological limitations temper the strength of this conclusion. Clinicians are cautioned against routinely treating children and adolescents with one or more prior injuries differently and more conservatively, because doing so, in some cases, might be counterproductive.
Keywords: mild traumatic brain injury; outcome research; persistent post-concussion symptoms; prognosis; sport-related concussion.