Posttraumatic Stress Disorder-Associated Cognitive Deficits on the Repeatable Battery for the Assessment of Neuropsychological Status in a Veteran Population

Cognitive Measures

All veterans completed a targeted cognitive battery that included the following: a reading recognition measure designed to estimate premorbid intellectual functioning (Wechsler Test of Adult Reading [WTAR]); a measure assessing auditory attention and working memory ability (Wechsler Adults Intelligence Scale-IV [WAIS-IV] Digit Span subtest); a measure assessing processing speed, attention, and cognitive flexibility (Trails A and B); and the RBANS.^16,30-32The focus of the current study was on the RBANS, a brief cognitive screening measure that contains 12 subtests examining a variety of cognitive functions. Given that all participants were veterans receiving outpatient services, there was no nonpatient control group for comparison. To address this, all raw data were converted to standardized scores based on healthy normative data provided within the test manual. Specifically, the 12 RBANS subtest scores were converted to age-corrected standardized z scores, which in turn created a total summary score and 5 composite summary indexes: immediate memory, visuospatial/constructional, attention, language, and delayed memory. All veterans completed the Form A version of the measure.

Statistical Analyses

Group level differences on selective demographic and cognitive measures between veterans with a diagnosis of PTSD and those without were examined using t tests. Cognitive variables included standardized scores for the RBANS, including age-adjusted total summary score, index scores, and subtest scores.¹⁶ Estimated full-scale IQ and standardized summary scores from the WTAR, demographically adjusted standardized scores for the total time to complete Trails A and time to complete Trails B, and age-adjusted standardized scores for the WAIS-IV Digit Span subtest (forward, backward, and sequencing trials, as well as the summary total score) were examined for group differences.^30,31,33 To further examine the association between PTSD and RBANS performance, multivariate multiple regressions were conducted using measures of episodic memory and processing speed from the RBANS (ie, story tasks, list learning tasks, and coding subtests). These specific measures were selected ad hoc based on extant literature.^6,10The dependent variable for each analysis was the standardized score from the selected subtest; PTSD status, a diagnosis of TBI, a diagnosis of co-occurring TBI and PTSD, gender, and years of education were predictor variables.

Results

Of the 153 study participants, 98 (64%) met DSM-4 criteria for current PTSD, whereas 55 (36%) did not (Table). There was no group statistical difference between veterans with or without a diagnosis of PTSD for age, education, or gender (P < .05). A diagnosis of PTSD tended to be more frequent in participants with a history of head injury (χ² = 7.72; P < .05). Veterans with a diagnosis of PTSD performed significantly worse on the RBANS Story Recall subtest compared with the results of those without PTSD (t[138] = 3.10; P < .01); performance on other cognitive measures was not significantly different between the PTSD groups. A diagnosis of PTSD was also significantly associated with self-reported depressive symptoms (Beck Depression Inventory-II; t[123] = -2.81; P < .01). Depressive symptoms were not associated with a history of TBI, and group differences were not significant.

Given the high co-occurrence of PTSD and TBI (68%) in our PTSD sample, secondary analyses examined the association of select diagnoses with performance on the RBANS, specifically veterans with a historical diagnosis of TBI (n = 92) from those without a diagnosis of TBI (n = 61), as well as those with co-occurring PTSD and TBI (n = 71) from those without (n = 82). The majority of the sample met criteria for a history of mild TBI (n = 79) when compared with moderate TBI (n = 13); none met criteria for a past history of severe TBI. PTSD status (β = .63, P = .04) and years of education (β = .16, P < .01) were associated with performance on the RBANS Story Recall subtest (R²= .23, F[5,139] = 8.11, P < .01). Education was the only significant predictor for the rest of the multivariate multiple regressions (all P < .05). A diagnosis of TBI or co-occurring PTSD and TBI was not significantly associated with performance on the Story Memory, Story Recall, List Learning, List Recall, or Coding subtests. multivariate analysis of variance tests for the hypothesis of an overall main effect of PTSD (F(5,130) = 1.08, P = .34), TBI (F[5,130] = .91, P = .48), or PTSD+TBI (F[5,130] =.47, P = .80) on the 4 selected tests were not significant.