The purpose of this study was to examine the influence of poor effort on neuropsychological test performance in military personnel following mild traumatic brain injury (MTBI). Participants were 143 U.S. service members who sustained a TBI, divided into three groups based on injury severity and performance on the Word Memory Test and four embedded markers of poor effort: MTBI-pass (n = 87), MTBI-fail (n = 21), and STBI-pass (n = 35; where STBI denotes severe TBI). Patients were evaluated at the Walter Reed Army Medical Center on average 3.9 months (SD = 3.4) post injury. The majority of the sample was Caucasian (84.6%), was male (93.0%), and had 12+ years of education (96.5%). Measures included the Personality Assessment Inventory (PAI) and 13 common neurocognitive measures. Patients in the MTBI-fail group performed worse on the majority of neurocognitive measures, followed by the Severe TBI-Pass group and the MTBI-pass group. Using a criterion of three or more low scores <10th percentile, the MTBI-fail group had the greatest rate of impairment (76.2%), followed by the Severe TBI-Pass group (34.3%) and MTBI-pass group (16.1%). On the PAI, the MTBI-fail group had higher scores on the majority of clinical scales (p < .05). There were a greater number of elevated scales (e.g., 5 or more elevated mild or higher) in the MTBI-fail group (71.4%) than in the MTBI-pass group (32.2%) and Severe TBI-Pass group (17.1%). Effort testing is an important component of postacute neuropsychological evaluations following combat-related MTBI. Those who fail effort testing are likely to be misdiagnosed as having severe cognitive impairment, and their symptom reporting is likely to be inaccurate.

The purpose of this study was to compare the neuropsychological outcome from blast-related versus non-blast related mild traumatic brain injury (MTBI). Participants were 56 U.S. military service members who sustained an MTBI, divided into two groups based on mechanism of injury: (a) non-blast related (Non-blast; n 5 21), and (b) blast plus secondary blunt trauma (Blast Plus; n 5 35). All participants had sustained their injury in theatre whilst deployed during Operation Iraqi Freedom or Operation Enduring Freedom. Patients had been seen for neuropsychological evaluation at Walter Reed Army Medical Center on average 4.4 months (SD 5 4.1) post-injury. Measures included 14 clinical scales from the Personality Assessment Inventory (PAI) and 12 common neurocognitive measures. For the PAI, there were no significant differences between groups on all scales (p. .05). However, medium effect sizes were found for the Depression (d 5 .49) and Stress (d 5 .47) scales (i.e., Blast Plus. Non-blast). On the neurocognitive measures, after controlling for the influence of psychological distress (i.e., Depression, Stress), there were no differences between the Non-blast and Blast Plus groups on all measures. These findings provide little evidence to suggest that blast exposure plus secondary blunt trauma results in worse cognitive or psychological recovery than blunt trauma alone.

The purpose of this study was to identify factors that are predictive of, or associated with, postconcussion symptom reporting after traumatic brain injury (TBI) in the U.S. military. Participants were 125 U.S. military service members (age: M=29.6 years, standard deviation [SD]=8.9, range=18-56 years) who sustained a TBI, divided into two groups based on symptom criteria for postconcussional disorder (PCD): PCD-Present (n=65) and PCD-Absent (n=60). Participants completed a neuropsychological evaluation at Walter Reed Army Medical Center (M=9.4 months after injury, SD=9.9; range: 1.1 to 44.8). Factors examined included demographic characteristics, injury-related variables, psychological testing, and effort testing. There were no significant group differences for age, sex, education, race, estimated premorbid intelligence, number of deployments, combat versus non-combat related injury, or mechanism of injury (p>0.098 for all). There were significant main effects for severity of body injury, duration of loss of consciousness, duration of post-traumatic amnesia, intracranial abnormality, time tested post-injury, possible symptom exaggeration, poor effort, depression, and traumatic stress (p<0.044 for all). PCD symptom reporting was most strongly associated with possible symptom exaggeration, poor effort, depression, and traumatic stress. PCD rarely occurred in the absence of depression, traumatic stress, possible symptom exaggeration, or poor effort (n=7, 5.6%). Many factors unrelated to brain injury were influential in self-reported postconcussion symptoms in this sample. Clinicians cannot assume uncritically that endorsement of items on a postconcussion symptom checklist is indicative of residual effects from a brain injury.