neuropsychologic effects: lower scores on tests of attention, working memory, executive function, verbal learning, and visual memory retention; more distress from confusion and tension, but higher proficiency in simple reaction time.

Secondary Studies

Four secondary studies addressed whether Gulf War-deployed veterans differed from nondeployed veterans (Axelrod and Milner 1997; Lindem et al. 2003; Vasterling et al. 2003; White et al. 2001), and a further study examined cognitive function in exercises designed to simulate the stress of combat (Lieberman et al. 2005b). Only Axelrod and Milner (1997) found reliable differences in neurobehavioral test performance between the groups after correction for age and education.

Lindem et al. (2003) found that Gulf War-deployed veterans who scored poorly on the Test of Memory Malingering (TOMM), which assesses motivation to perform well, had lower scores on neuropsychologic tests of attention, executive function, and memory. Their study is part of a larger study begun by McEwen (2004) to compare veterans recruited from three cohorts: Fort Devens and New Orleans (n = 58), and 19 Germany-deployed veterans from a Maine National Guard unit. There were no significant differences in mean TOMM scores between the Gulf War-deployed and the Germany-deployed groups. Those who scored lower on the TOMM had a greater prevalence of lifetime PTSD (13.6%) than those with higher scores (1.8%). White et al. (2001) used a larger sample of the McEwen study cohorts from Fort Devens and from New Orleans (total n = 193) and compared them to 47 Germany-deployed veterans. No differences in neuropsychologic test performance were seen between the Gulf War-deployed and Germany-deployed troops, but poorer performance on cognitive tests in Gulf War-deployed veterans was associated with self-reports of exposure to chemical-warfare agents. Similar results were seen in a small study by Vasterling et al. (2003), who found that Gulf War-deployed veterans reported more concerns about cognitive functioning than nondeployed veterans, but those concerns were not confirmed by neurocognitive measures. A study by Lieberman et al. (2005a) found significant (p < 0.001) decrements in cognitive function, vigilance, reaction time, attention, memory, and reasoning during stressful combat-like training compared with baseline prestress performance in 31 U.S. Army officers who had volunteered for an intense training exercise.

Posttraumatic Stress Disorder and Neurocognitive and Neurobehavioral Effects

The committee identified three analyses of Vietnam veterans drawn from the CDC VES and seven secondary studies that examined the relationship between PTSD and neurocognitive and neurobehavioral outcomes. Barrett et al. (1996) used information from the VES to compare cognitive impairment from PTSD and other psychiatric diagnoses in Vietnam veterans. The 2441 veterans were categorized as to whether they had lifetime PTSD and whether the PTSD was comorbid with a current diagnosis of another psychiatric disorder, using the DIS. Several neurobehavioral tests—the California Verbal Learning Test (CVLT), the Rey-Osterrieth Complex Figure Drawing Test, the Wisconsin Card Sorting Test (WCST), and the Wechsler Adult Intelligence Scale-Revised (WAIS-R)—were administered to all participants. Results indicate that PTSD alone was not associated with impairment in cognition; however, veterans with PTSD and current depression, anxiety, or substance use (n = 128) had lower scores on all tests of cognitive functioning than veterans with PTSD alone (n = 236), veterans with only

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