another psychiatric diagnosis (n = 242), and veterans with no psychiatric diagnoses (n = 1835). After adjustment for military and demographic characteristics, results suggest that cognitive deficits might be associated with concomitant diagnoses of PTSD and another psychiatric disorder.

Crowell et al. (2002) examined the influence of combat-related PTSD on neurocognitive functioning in a randomly selected subsample of middle-aged Vietnam Army veterans from the VES. Veterans were categorized as having current PTSD (n = 80), having PTSD in the preceding year but without current symptoms (n = 80), psychiatric controls with a DSM-III diagnosis but not PTSD (n = 80), and normal controls (n = 80). PTSD was diagnosed with the DIS-III-A. All veterans completed the WAIS-R, CVLT, Rey-Osterrieth Complex Figure Drawing Test, the Paced Auditory Serial Addition Test (PASAT), the Word List Generation Tasks, the WCST, and the Grooved Pegboard Test. After control for demographic characteristics and comorbid psychiatric conditions, the four groups showed no appreciable differences in cognitive functioning.

Zalewski et al. (1994) also used data from the VES to compare neuropsychologic performance in 241 Vietnam veterans with PTSD, those with GAD (n = 241), those with no history of psychiatric illness (n = 241). Comorbid psychiatric disorders—primarily substance abuse or dependence—were present in 80% of the PTSD group and 72% of the GAD group. Cognitive functioning was measured with the WAIS-R block design subtest, the CVLT, the Rey-Osterrieth Complex Figure Drawing Test, and the PASAT. A one-way multivariate analysis of variance revealed no significant differences among the three groups on independent measures of cognitive function.

The secondary studies addressed whether veterans with PTSD differed from veterans without a PTSD diagnosis. Findings were inconsistent; when results were positive in the numerous studies described below, the domains that were most often affected pertained to attention and memory.

In a small study of 32 Vietnam combat veterans, Gilbertson et al. (2001) found that although veterans with PTSD demonstrated poorer performance on most of the neurocognitive tests, only attention and memory were significant (p = 0.003) predictors of PTSD status in combat veterans. Similarly, Koso and Hansen (2006) found cognitive impairments with large effect sizes pertaining to attention, working memory, executive function, and memory in 20 Bosnian male combat veterans with PTSD, age- and intelligence-matched to veterans without PTSD.

Uddo et al. (1993) found that Vietnam veterans with PTSD had memory and attention deficits, and two studies by Vasterling et al. found attention and memory deficits to be associated with PTSD in Gulf War veterans (Vasterling et al. 1998) and in Vietnam veterans (Vasterling et al. 2002) even when they controlled for combat exposure. Yehuda et al. (1995) demonstrated that combat veterans with PTSD have specific deficits in memory related to retroactive interference and a decrement in retention although they have normal abilities in initial attention, immediate memory, and cumulative learning and active inference from previous learning.

Finally, Vasterling et al. (2000) sought to determine whether dysfunction of the frontolimbic system of the brain was implicated in PTSD. They compared 51 Vietnam-combat veterans with and without PTSD (n = 26 and n = 25, respectively) with 17 Vietnam-era veterans without a psychiatric disorder. The University of Pennsylvania Smell Identification Test, the Continuous Performance Test, the Auditory-Verbal Learning Test, and the WCST were used to determine cognitive functioning. Olfactory identification was used to assess orbitofrontal



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