Date of Award
Fall 2019
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Psychology
First Advisor
Hoelzle, James B.
Second Advisor
Grych, John
Third Advisor
Magnus, Brooke
Abstract
Mild traumatic brain injuries (MTBIs) result in a constellation of non-specific physical, cognitive, and psychological symptoms. There is significant variability in neurocognitive recovery after MTBI, ranging from a few days to a few months, and others who fail to make complete recovery. A broad literature has attempted to elucidate what individual differences explain this variability. The present study sought to build upon previous meta-analyses, which systematically aggregated and examine relevant literature, by including a more heterogenous population and utilizing contemporary meta-analytic techniques. Three online databases (PsychINFO [sic], PubMed, MedLine) were searched for pertinent studies. Separate random-effects Analogue-to-ANOVA were utilized to examine the overall neurocognitive effects of MTBI across time points, stratified by age, psychological comorbidity, populations of interest (athletes, general medical referrals, Veterans, litigants), and whether performance validity tests (PVT) were utilized. Subsequent analyses utilized meta-regressive techniques to simultaneously examine the variables of interest. After article review, 109 studies were retained for analysis (NMTBI = 5919, NControl = 8318). Analogue-to-ANOVA analyses revealed a medium-large overall neurocognitive effect size in the first 24 hours post-injury (d = .64) that decreased to a small effect size over the first 90 days (d = .24). Driven by a higher number of Veteran and litigant samples, the effect size increased in the post-acute period (> 90 days; d = .39). Veteran samples were observed to have significantly larger effect sizes than other populations considered. Meta-regressive analyses found that, across heterogenous populations, time since injury (TSI) was predictive of overall cognitive function only prior to 90 days post-injury, but not in the post-acute period. Psychological functioning was the most important predictor of cognitive functioning after MTBI (β = .47), over and above TSI, population, demographic variables, injury parameters, age, or PVT. This study is consistent with the growing research suggesting that psychological functioning largely explains MTBI recovery and suggests that assessment of emotional well-being and psychological functioning should be part of routine clinical care for the management of MTBI.