A Meta-Analysis of Neuropsychological Outcome After Mild Traumatic Brain Injury: Re-analyses and Reconsiderations of Binder et al. (1997), Frencham et al. (2005), and Pertab et al. (2009)

Abstract

The meta-analytic findings of Binder et al. (1997) and Frencham et al. (2005) showed that the neuropsychological effect of mild traumatic brain injury (mTBI) was negligible in adults by 3 months post injury. Pertab et al. (2009) reported that verbal paired associates, coding tasks, and digit span yielded significant differences between mTBI and control groups. We re-analyzed data from the 25 studies used in the prior meta-analyses, correcting statistical and methodological limitations of previous efforts, and analyzed the chronicity data by discrete epochs. Three months post injury the effect size of −0.07 was not statistically different from zero and similar to that which has been found in several other meta-analyses (Belanger et al., 2005; Schretlen & Shapiro, 2003). The effect size 7 days post injury was −0.39. The effect of mTBI immediately post injury was largest on Verbal and Visual Memory domains. However, 3 months post injury all domains improved to show non-significant effect sizes. These findings indicate that mTBI has an initial small effect on neuropsychological functioning that dissipates quickly. The evidence of recovery in the present meta-analysis is consistent with previous conclusions of both Binder et al. and Frencham et al. Our findings may not apply to people with a history of multiple concussions or complicated mTBIs.

Keywords:

• Traumatic brain injury
• Meta-analysis
• Post concussion
• Effect size calculations

Notes

¹ For the sake of consistency, in this paper a negative effect size indicates better performance by the control group than the mTBI group, regardless of the definition of negative effect size in previous studies. Some previously published papers, including Binder et al. (1997), defined effect sizes in the reverse direction. For example, Binder et al. (1997) reported an effect size of –0.07 showed a negligible superiority of controls over mTBI cases, but in the present paper, the same effect size is reported as –0.07.