Effects of Pediatric Traumatic Brain Injury on Verbal IQ: A Systematic Review and Meta-Analysis

Objectives: To examine the effects of pediatric traumatic brain injury (TBI) on verbal IQ by severity and over time. Methods: A systematic review and subsequent meta-analysis of verbal IQ by TBI severity were conducted using a random effects model. Subgroup analysis included two epochs of time (e.g., <12 months postinjury and ≥12 months postinjury). Results: Nineteen articles met inclusion criteria after an extensive literature search in MEDLINE, PsycInfo, Embase, and CINAHL. Meta-analysis revealed negative effects of injury across severities for verbal IQ and at both time epochs except for mild TBI < 12 months postinjury. Statistical heterogeneity (i.e., between-study variability) stemmed from studies with inconsistent classification of mild TBI, small sample sizes, and in studies of mixed TBI severities, although not significant. Risk of bias on estimated effects was generally low (k = 15) except for studies with confounding bias (e.g., lack of group matching by socio-demographics; k = 2) and measurement bias (e.g., outdated measure at time of original study, translated measure; k = 2). Conclusions: Children with TBI demonstrate long-term impairment in verbal IQ, regardless of severity. Future studies are encouraged to include scores from subtests within verbal IQ (e.g., vocabulary, similarities, comprehension) in addition to functional language measures (e.g., narrative discourse, reading comprehension, verbal reasoning) to elucidate higher-level language difficulties experienced in this population.