Influence of poor effort on self-reported symptoms and neurocognitive test performance following mild traumatic brain injury

Abstract

When considering a diagnosis of postconcussion syndrome, clinicians must systematically evaluate and eliminate the possible contribution of many differential diagnoses, comorbidities, and factors that may cause or maintain self-reported symptoms long after mild traumatic brain injury (MTBI). One potentially significant contributing factor is symptom exaggeration. The purpose of the study is to examine the influence of poor effort on self-reported symptoms (postconcussion symptoms and cognitive complaints) and neurocognitive test performance following MTBI. The MTBI sample consisted of 63 referrals to a concussion clinic, evaluated within 5 months post injury (M = 2.0, SD = 1.0, range = 0.6–4.6), who were receiving financial compensation from the Workers' Compensation Board. Participants completed the Post-Concussion Scale (PCS), British Columbia Cognitive Complaints Inventory (BC-CCI), selected tests from the Neuropsychological Assessment Battery Screening Module (S-NAB), and the Test of Memory Malingering (TOMM). Participants were divided into two groups based on TOMM performance (15 fail, 48 pass). There were significant main effects and large effect sizes for the PCS (p = .002, d = 0.79) and BC-CCI (p = .011, d = 0.98) total scores. Patients in the TOMM fail group scored higher than those in the TOMM pass group on both measures. Similarly, there were significant main effects and/or large effect sizes on the S-NAB. Patients in the TOMM fail group performed more poorly on the Attention (p = .004, d = 1.26), Memory (p = .006, d = 1.16), and Executive Functioning (p > .05, d = 0.70) indexes. These results highlight the importance of considering the influence of poor effort, in conjunction with a growing list of factors that can influence, maintain, and/or mimic the persistent postconcussion syndrome.

Keywords:

• Postconcussion symptoms
• Response bias
• Symptom validity testing
• Test of Memory Malingering

A portion of these data was presented at the International Neuropsychological Society conference, February 2010, Acapulco, Mexico. This research was granted ethical clearance by the University of British Columbia Behavioral Research Ethics Board.

Notes

¹It is important to note that postconcussional disorder is not an official DSM–IV diagnostic category. DSM–IV presents only research criteria for postconcussional disorder in an effort to provide a common language for researchers and clinicians who are interested in studying this disorder. At the time of development of the DSM–IV, criteria for postconcussional disorder were proposed but were not included as an official category due to a lack of sufficient information (see American Psychiatric Association, 2000, p. 759, for more information).

²Several T scores are derived for the Numbers and Letters A test, including two separate scores for speed and errors. These two scores are combined into an efficiency score. The efficiency, but not speed and error, T score was included in the present analyses.

³The analyses in this study were also run without the inclusion of these 2 participants. There was not a difference on the outcome of the main findings.

⁴A cutoff score of the 16th percentile was chosen for illustrative purposes only. Scores falling less than the 1st, 5th, and 10th percentiles were also calculated but were not included due to the low prevalence of scores in this range and due to page limitations. These data are available from the first author on request.