Posttraumatic Stress Symptoms and General Activity Level in the ...

P1: Vendor/GDX International Journal of Rehabilitation and Health [ijrh]

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Style file version Nov. 19th, 1999

International Journal of Rehabilitation and Health, Vol. 5, No. 1, 2000

Posttraumatic Stress Symptoms and General Activity Level in the Prediction of Neurocognitive Performance in Chronic Pain Patients Stacy Thomas,1 Tony Iezzi,1 Melanie P. Duckworth,2,4 Yvonne Archibald,3 and Ann Klinck3

The relative contribution of posttraumatic stress symptoms and general activity level to the prediction of neurocognitive performance among individuals with chronic pain was investigated. Posttraumatic stress symptoms accounted for significant proportions of the variance in attention and concentration and memory after controlling for years of education and pain severity. Level of engagement in common daily activities was also a significant predictor of attention and concentration. Level of general activity moderated the relation between posttraumatic stress symptoms and reasoning ability, the expected negative relation between posttraumatic stress symptoms and reasoning ability was significant only among those chronic pain patients who reported low levels of engagement in tasks of daily living. Discussion focuses on the findings in terms of their many implications for assessment and treatment of emotional and neurocognitive difficulties experienced by persons with chronic pain. KEY WORDS: chronic pain; neurocognitive performance; posttraumatic stress.

Individuals with chronic pain often report neurocognitive difficulties. Yet, relatively few studies have examined neurocognitive functioning in this patient population. This is surprising given the potential negative impact of neurocognitive difficulties on the ability of chronic pain patients to follow and make use of treatment interventions. There are a number of aspects of the chronic pain experience that could influence neurocognitive functioning. First, there is the somatosensory experience of pain. Patients often complain that distraction due to pain interferes with tasks of daily living such as reading comprehension, their ability to follow conversations, and their ability to organize and complete everyday tasks in an efficient manner. In addition to the somatosensory experience of chronic pain, chronic pain patients present with high levels of emotional distress. Although an association exists between pain severity and level of emotional distress, there 1 Behavioral

Medicine Service, London Health Sciences Centre, London, Ontario, Canada. of Psychology, University of Houston, Houston, Texas. 3 Neuropsychology Service, London Health Sciences Centre, London, Ontario, Canada. 4 To whom correspondence should be addressed at Department of Psychology, University of Houston, 4800 Calhoun Road, Houston, Texas, 77204-5341; e-mail: [email protected]. 2 Department

31 C 2000 Plenum Publishing Corporation 1068-9591/00/0100-0031$18.00/0 °


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Thomas, Iezzi, Duckworth, Archibald, and Klinck

is evidence that these variables are independent predictors of performance on neurocognitive tasks. Iezzi and colleagues (Iezzi et al., 1999a,b) examined the relative contribution of pain severity and emotional distress to neurocognitive functioning in patients with chronic pain. One of the strengths of these studies was the use of objective and standardized measures to evaluate a wide range of neurocognitive domains: attention and concentration, memory, reasoning ability, and constructional ability. Evaluating the contribution of pain severity and emotional distress to neurocognitive performance, these researchers determined that, after controlling for age and years of education, self-reports of pain severity accounted for a significant proportion of the variance in performance on measures of constructional ability and memory. Self-reported emotional distress predicted significant additional variance in performance on memory tasks over and above pain severity. Moreover, of the two predictors, only emotional distress was a significant predictor of performance on measures of reasoning ability after statistically controlling for the variance accounted for by demographic variables. Thus, although chronic pain patients often identify physical pain as the primary cause of cognitive difficulties, evidence suggests that emotional distress may also have a significant and unique impact on aspects of their neurocognitive performance. We examined relative contributions of pain and emotional distress to neurocognitive functioning in patients with chronic pain. However, rather than investigating the predictive value of measures of global psychological distress, we examined the relation between posttraumatic stress symptoms and neurocognitive performance. Numerous studies have shown that posttraumatic stress symptoms and chronic pain co-occur following accidental or work-related injury (Asmundson et al., 1998; Benedikt and Kolb, 1986; Geisser et al., 1996; Hickling and Blanchard, 1992; Kuch et al., 1991). Regardless of the nature of events associated with the onset of chronic pain, the psychosocial impact of the chronic pain experience can be traumatic. Furthermore, there are a number of studies which indicate that individuals with a history of trauma demonstrate reduced neurocognitive performance on measures of attention, memory, and executive functioning (Bremner et al., 1993; Knight, 1997; Tartar et al., 1984; Uddo et al., 1993). Researchers have assessed emotional impact of trauma in a number of ways, including structured clinical interviews and self-report scales (Norris and Riad, 1997). The Minnesota Multiphasic Personality Inventory Posttraumatic Stress Disorder Scale (MMPI-Pk scale; Keane et al., 1984) is one of the earliest measures of posttraumatic stress symptoms, and research has found it to be a reliable and valid tool for distinguishing traumatized from nontraumatized individuals (e.g., Hovens and van der Ploeg, 1993; Keane et al., 1984; Koretsky and Peck, 1990). Given the relevance of trauma to chronic pain patients, the MMPI-2 version of the Pk scale was used to examine the relation between posttraumatic stress symptoms and neurocognitive functioning in this population. The extent to which chronic pain patients engage in activities of daily living may also be important for understanding their neurocognitive functioning. Relatively high levels of general activity with respect to involvement in household chores, social activities, and activities away from home may indicate that a chronic pain patient has adequate neurocognitive abilities. Remaining involved in activities of daily life may also be a useful way of reducing stress associated with experiencing chronic physical pain as well as with the lifestyle disruption inherent to the chronic pain experience.


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Physiological hyperarousal is common to both chronic pain (Melzack, 1999) and posttraumatic stress disorder (PTSD) (van der Kolk, 1996). There is some evidence that suggests an association between chronic hyperarousal and greater exposure to norandrenergic stresshormones, which are thought to have adverse effects on brain structures involved in memory, attention, and executive functioning (Knight, 1997; van der Kolk, 1996). Chronic pain patients, either because of actual physical limitations or because of their fear of causing more physical damage, tend to be less active than pain-free individuals (Asmundson et al., 1999). The impact of high levels of arousal on neurocognitive functions of individuals with chronic pain may be greatest among those who cannot or do not make use of outlets for expending “nervous energy.” Our aim was to investigate the relative contribution of posttraumatic stress symptoms and general activity level to the prediction of neurocognitive performance among individuals with chronic pain after taking into account the influence of education and pain severity. We expected to find higher levels of posttraumatic stress symptoms and lower levels of general activity associated with poorer performance on tasks measuring the neurocognitive domains of attention and concentration, memory, reasoning ability, and constructional ability. We also performed exploratory analyses investigating the moderating influence of general activity on the relation of posttraumatic stress symptoms to neurocognitive performance.

METHOD Participants The original sample consisted of 73 chronic pain patients. We deleted four outliers, identified through univariate analyses, resulting in a final sample of 69 participants (28 males, 41 females) ranging in age from 22 to 67 years (M = 40.1, SD = 8.9) and reporting an average of 12.5 years of formal education (SD = 2.4). We recruited participants consecutively from a pain service in a general medical hospital, with referrals coming from a number of medical services (e.g., physical medicine and rehabilitation, neurology, and internal medicine). Inclusion criteria for this study were nonmalignant pain, regional or general pain, and pain of a musculoskeletal nature (e.g., fibromyalgia, chronic myofascial neck, back, and head pain, and osteoarthritis of the spine or proximal joints). In addition, pain had to be present on a daily basis and occur for 6 months or greater. Most participants (75%) were on at least one medication and a little more than half the sample (52%) were on two or more classes of medication (e.g., opioids, antidepressants, and muscle relaxants). Thirteen percent of participants were either working or studying full-time, 7% were working or studying part-time, 6% were unemployed, 37% were receiving a disability pension, 18% were involved in a legal suit, and 19% were receiving Worker’s Compensation. We had excluded participants with a history of psychosis or major depression not secondary to chronic pain, a history of neuropathic pain syndrome (e.g., reflex sympathetic dystrophy), a history of chronic but episodic pain (e.g., migraines), or a history of documented changes in cognitive function subsequent to traumatic brain injury or other known brain impairment. All participants meeting inclusion criteria agreed to participate in the study. Incentives for study participation included the opportunity to be involved in psychological pain management as well as provision of cost-free neurocognitive evaluation and feedback.


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Materials Psychological Distress The Minnesota Multiphasic Personality Inventory-2 (MMPI-2; Butcher et al., 1989) is a 567-item, true–false, self-report instrument that assesses emotional distress. It has three validity scales (Lie—L, Frequency—F, and Correction—K) and ten clinical scales (Hypochondriasis—Hs, Depression—D, Hysteria—Hy, Psychopathic Deviate—Pd, Masculinity–Femininity—Mf, Paranoia—Pa, Psychasthenia—Pt, Schizophrenia—Sc, Mania—Ma, and Social Introversion—Si). We obtained an index of posttraumatic stress symptoms from the MMPI-2 Pk scale (Keane et al., 1984). Pain Severity We obtained ratings of pain severity and general activity level from the Multidimensional Pain Inventory (MPI; Kerns et al., 1985). The MPI is a nine-scale, 61-item measure of behavioral and psychosocial responses to chronic pain. The MPI Pain Severity (MPI-PS) scale consists of three items and has an internal consistency of .72. The MPI General Activity Level scale consists of four MPI subscales that assess outdoor work, housework, social activity, and activity away from home. Internal consistency estimates for the four subscales range from .83 to .91. Neurocognitive Test Battery We selected a comprehensive battery of standardized neuropsychological tests to assess neurocognitive performance in chronic pain patients. Included in the battery of tests were measures of intelligence, attention and concentration, cognitive efficiency, memory, visuospatial and constructional functions, verbal and nonverbal fluency, flexibility of thinking, and manual dexterity. Ten tests constituted the neurocognitive assessment. We used the Wechsler Adult Intelligence Scale-Revised (WAIS-R; Wechsler, 1981) to assess overall intellectual functioning. The WAIS-R consists of 11 subtests reflecting verbal and performance intelligence: Information, Digit Span, Vocabulary, Arithmetic, Comprehension, Similarities, Picture Completion, Picture Arrangement, Block Design, Object Assembly, and Digit Symbol. The average reliability coefficients for Verbal, Performance, and Full IQ range from .93 to .97. We used the Wechsler Memory Scale-Revised (WMS-R; Wechsler, 1987) Logical Memory and Visual Reproduction subtests to assess different dimensions of memory, registration and retrieval of auditory and verbal material, and immediate and delayed reproduction of visuospatial material. Split-half reliability estimates range from .60 to .80 for immediate logical memory and from .55 to .85 for delayed logical memory. For immediate visual reproduction, internal consistency coefficients range from .46 to .71. For delayed visual reproduction, consistency estimates range from .38 to .59. We used the Rey–Osterreith Figure Test (RFT; Osterreith, 1944; Rey, 1941) copy and immediate recall scores to assess visuospatial and constructional ability and visual memory. Interrater reliability for scoring ranges from .91 to .98. We used the Stroop Color


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and Word Test (SCWT; Golden, 1978) to measure the ease with which an individual can shift perceptual set to conform to changing demands and suppress a habitual response in favor of an unusual one. The measure used was the color-word score because it best reflects the ability to shift set and focus concentration. This score consists of the number of printed color words read in a specific time period when the print ink is of a different color. We used the Wisconsin Card Sorting Test (WCST; Heaton, 1981) to measure concept formation and shifting and maintaining set. Number of categories is one of the most widely used WCST scores and is the one we selected for use in our study. We used the Paced Auditory Serial Addition Test (PASAT; Gronwall and Sampson, 1974) as a measure of information processing and sustained attention. Internal consistency is high with a split-half reliability of .96. We included Form B of the Trail Making Test (TMT; Spreen and Benton, 1965) as a measure of speed for visual search, attention, mental flexibility, and motor functions. The reported coefficient of concordance is .67. We used the Design Fluency Test (DFT; Jones-Gottman and Milner, 1977) as a measure of nonverbal fluency. This test requires self-monitoring, remembering and following rules, youth of strategies as well as creativity. Both free and fixed conditions of the DFT involve generating novel designs according to certain rules. However, in the fixed condition, acceptable drawings must be no more than four lines, straight or curved. Reliability ratings for interjudge scoring range from .74 to .87. The Controlled Oral Word Association Test (COWA; Benton and Hamsher, 1978) measures production of individual words under restricted search conditions. It also involves self-monitoring (to avoid repetition), remembering and following rules, and use of strategies. The Grooved Pegboard Test (GPT; Matthews and Klove, 1964) measures manual dexterity and coordination.

Procedure Participants completed the MMPI-2, MPI, and neurocognitive test battery as part of a study examining the relation between emotional distress and neurocognitive performance in chronic pain patients. We counter-balanced completion of self-report measures with presentation of neurocognitive measures. The test protocol took approximately 3–3.5 h to complete. Participants returned for a 1-hour feedback session of test results.

Data Screening and Statistical Analyses We used SPSS for Windows (Version 7.5; Norusis, 1996) for all analyses. Prior to data analysis, we examined scores reflecting age, education, pain severity, posttraumatic stress symptoms, general activity level, and neurocognitive performance for accuracy of data entry, missing values, univariate outliers, and normality of distribution. We identified four outliers through univariate analyses. We deleted all four outliers, with 69 cases available for analysis. Significant skewness and kurtosis were evident in the distribution of three of the neurocognitive performance variables: RFT, TMT, and WCST. To reduce skewness and kurtosis, we performed square root and logarithmic transformations on these variables. Neither transformation technique resulted in significant improvement in skewness or kurtosis. For this reason and because of the increased ease of interpretation associated with


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nontransformed scores (Tabachnick and Fidell, 1996), we used nontransformed RFT, TMT, and WCST scores in all analyses. We combined the neurocognitive variables to reflect four theoretically derived neurocognitive domains, factorially validated in previous research by Iezzi et al. (1999a,b). These neurocognitive domains include: attention and concentration (TMT, SCWT, WAIS-R Arithmetic, and WAIS-R Digit Span), memory (WMS-R Logical Memory immediate and delayed recall and Visual Reproduction immediate and delayed recall), reasoning ability (WAIS-R Picture Arrangement, WAIS-R Similarities, and WCST), and constructional ability (RFT, WAIS-R Block Design). The neurocognitive domains of attention and concentration, memory, and reasoning ability demonstrated adequate internal consistency, with Cronbach’s alphas ranging from .66 to .79. However, internal consistency of the constructional ability domain was quite low (Cronbach’s alpha = .42). We used all four neurocognitive domains as criterion variables in correlational and hierarchical multiple regression analyses; however, findings pertaining to constructional ability are limited by the low internal consistency revealed for this domain. Descriptive statistics for predictor variables and for each of the neurocognitive tasks and broad neurocognitive domains appear in Table I. We centered all predictors used in hierarchical regression analyses in order to reduce collinearity between main effect and interaction terms (Aiken and West, 1991). We conducted follow-up tests of the simple slopes according to the procedure outlined by West et al. (1996). Table I. Descriptive Statistics for Demographic, Pain Severity, Posttraumatic Stress Symptoms, General Activity Level, and Neurocognitive Performance Variables Variable Age (years) Education (years) MPI-PS (T-score) MMPI-2 Pk (raw score) MPI-GAL (T-score) Attention and Concentration domain TMT (seconds, reverse scored) SCWT (number correct) WAIS-R Arithmetic (raw score) WAIS-R Digit Span (raw score) Memory domain WMS-R (percentile) Logical Memory—immediate Logical Memory—delayed Visual Reproduction—immediate Visual Reproduction—delayed Reasoning Ability domain WAIS-R Picture Arrangement (raw score) WAIS-R Similarities (raw score) WCST (number of categories) Constructional Ability domain RFT (copy scale score) WAIS-R Block Design (raw score)

Alpha

N

M

SD

Range

69 69 69 68 67

40.07 12.45 50.33 19.97 51.22

8.88 2.37 8.50 9.51 8.13

22–67 7–18 22.4–64.5 1–43 33.6–73.5

69 68 69 69

521 44.29 12.43 15.16

25.35 8.84 2.94 3.81

440–561 25–64 6–19 7–27

69 69 69 69

56.10 52.49 58.23 50.29

26.99 26.93 25.84 28.94

4–99 2–99 2–98 1–96

69 69 68

12.22 19.52 5.07

4.08 4.03 1.4

3–20 11–27 1–6

69 69

66.96 29.87

3.57 8.73

55–72 8–46

.66

.79

.68

.42

Note. MPI-PS = Multidimensional Pain Inventory Pain Severity scale, MMPI-2 Pk = Minnesota Multiphasic Personality Inventory-2 Posttraumatic Stress Disorder scale, MPI-GAL = Multidimensional Pain Inventory General Activity Level scale, TMT = Trails Making Test, SCWT = Stroop Color Word Test, WAIS-R = Wechsler Adult Intelligence Scale—Revised, WMS-R = Wechsler Memory Scale—Revised, WCST = Wisconsin Card Sorting Test, RFT = Rey–Osterreith Figure Test.


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Table II. Correlations among Demographic, Pain Severity, Posttraumatic Stress Symptoms, General Activity Level, and Neurocognitive Performance Variables Variable 1. Age (years) 2. Education (years) 3. Classes of medications 4. MPI-PS (T-Score) 5. MMPI-2 Pk (T-score) 6. MPI-GAL (T-score) 7. Attention and Concentration 8. Memory 9. Reasoning Ability 10. Constructional Ability

1

2

3

4

5

6

7

8

9

10

— −.12 .01 −.07 −.09 .12 −.04 −.04 −.04 −.07 — .09 −.27∗ .11 .19 .40∗∗ .30∗ .40∗∗ .35∗∗ — .13 −.06 .13 .01 .13 .15 .16 — .11 −.16 −.28∗ −.35∗ −.28∗ −.37∗ — −.07 −.22 −.27∗ −.19 −.01 .28∗ .25∗ .27∗ — .36∗∗ ∗∗ ∗∗ — .43 .39 .42∗∗ — .48∗∗ .42∗∗ — .44∗∗ —

Note. N s range from 67 to 69, MPI-PS = Multidimensional Pain Inventory Pain Severity scale, MMPI-2 Pk = Minnesota Multiphasic Personality-2 Posttraumatic Stress Disorder scale, MPI-GAL = Multidimensional Pain Inventory General Activity Level scale. ∗ p < .05; ∗∗ p < .01.

RESULTS Table II presents Pearson correlations among measures of age, education, pain severity, medication use, posttraumatic stress symptoms, general activity level, and the neurocognitive performance domains of attention and concentration, memory, reasoning ability, and constructional ability. Neither age nor the number of classes of medications used was significantly correlated with pain severity, posttraumatic stress symptoms, general activity level, or neurocognitive performance. Years of education was significantly correlated to reports of pain severity. Chronic pain patients with more years of education reported lower levels of pain than those with fewer years of formal education. Years of education was not related to patients’ reports of posttraumatic stress symptoms or general activity level. Chronic pain patients with more years of education performed better than chronic pain patients with few years of education on tasks assessing attention and concentration, memory, reasoning ability, and constructional ability. Lower levels of pain severity were also significantly associated with better performance on tasks measuring all four neurocognitive domains. As expected, general activity level was significantly positively related to performance in each of the neurocognitive domains; the more active these chronic pain patients reported being in their everyday lives, the better they performed on measures of attention and concentration, memory, reasoning ability, and constructional ability. In contrast to general activity level, predictions regarding the direct relation between measures of posttraumatic stress symptoms and neurocognitive performance received only partial support. Only the relation between posttraumatic stress and memory was statistically significant. Participants’ reporting a large number of posttraumatic stress symptoms evidenced poorer performance on memory tasks than did participants reporting a small number of posttraumatic stress symptoms. Also noteworthy was the lack of significant relations among measures of pain severity, emotional distress, and general activity level. We conducted hierarchical multiple regression analyses to examine whether measures of posttraumatic stress symptoms and general activity level were significant predictors of neurocognitive performance after statistically controlling for variance accounted for


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Table III. Hierarchical Regression of Education, Pain Severity, Posttraumatic Stress Symptoms, and General Activity Level Variables Predicting Neurocognitive Domains

R 2 change Step 1: Education (years) Step 2: MPI-PS (T-score) Step 2: MMPI-2 Pk (T-score) Step 3: MPI-GAL (T-score) Step 4: MMPI-2 Pk × MPI-GAL Total variance explained (R 2 ) F (full model) df (full model)

Attention and Concentration

Memory

Reasoning Ability

Constructional Ability

.17∗∗ .03 .05∗ .06∗ .02 .33∗∗∗ 5.88∗∗∗ 5, 60

.09∗ .08∗ .07∗ .03 .00 .27∗∗ 4.48∗∗ 5, 61

.17∗∗ .03 .04 .02 .10∗∗ .35∗∗∗ 6.50∗∗∗ 5, 60

.12∗∗ .08∗ .00 .03 .01 .24∗∗ 5.11∗∗ 5, 61

Note. MPI-PS = Multidimensional Pain Inventory Pain Severity scale, MMPI-2 Pk = Minnesota Multiphasic Personality-2 Pk scale, MPI-GAL = Multidimensional Pain Inventory General Activity Level scale. * p < .05; ∗∗ p < .01; ∗∗∗ p < .001.

by years of education and pain severity. We also examined the moderating influence of general activity level on the relation of posttraumatic stress symptoms to neurocognitive performance. As indicated in Table III, years of education accounted for significant proportions of variance in each of the neurocognitive domains of attention and concentration (17%), memory (9%), reasoning ability (17%), and constructional ability (12%). Pain severity accounted for significant unique proportions of variance in memory (8%) and constructional ability (8%). Measures of posttraumatic stress symptoms and general activity level also predicted significant proportions of variance in neurocognitive performance after statistically controlling for variance accounted for by years of education and pain severity. Posttraumatic stress symptoms predicted significant additional proportions of variance in attention and concentration (5%) and memory (7%). These relationships indicated that the higher the posttraumatic stress symptomatology, the worse these chronic pain patients performed on tasks measuring attention and concentration and memory. General activity level predicted a significant additional proportion of variance in attention and concentration (6%) after accounting for variance due to education, pain severity, and posttraumatic stress symptoms. This relation indicated that the more active chronic pain patients reported they were in their daily lives, the better they performed on attention and concentration tasks. Neither posttraumatic stress symptoms nor general activity level added significantly to the prediction of reasoning ability when entered into the regression model; however, the moderator variable derived from these two variables accounted for a significant additional proportion of the variance in reasoning ability (10%). As illustrated in Fig. 1, reported level of general activity moderated the relation between reports of posttraumatic stress symptoms and reasoning ability in chronic pain patients. Analysis of the simple effects at low (1 SD below the mean) and high (1 SD above the mean) levels of general activity indicated a significant negative relation between posttraumatic stress symptoms and reasoning ability only among those who reported low levels of general activity [b = −.13, t(65) = −3.47, p < .01]. Among patients who reported low levels of general activity, the greater their posttraumatic stress symptoms the worse they performed on


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Fig. 1. Posttraumatic Stress Symptoms and Reasoning Ability as a function of General Activity Level, after controlling for Education and Pain Severity.

reasoning tasks. Neither posttraumatic stress symptoms nor general activity level added significantly to the prediction of constructional ability. Results did not support general activity level as a moderator of the relation of posttraumatic stress symptoms to constructional ability.

DISCUSSION Our aim was to investigate the extent to which posttraumatic stress symptoms and general activity level contribute to the prediction of neurocognitive performance in chronic pain patients over and above the influence of education and pain severity. Hierarchical regression analyses used to evaluate this question confirmed the importance of posttraumatic stress symptoms and general activity level to understanding neurocognitive functioning among patients with chronic pain. After controlling for years of education and pain severity, posttraumatic stress symptoms accounted for significant variance in attention and concentration and memory. Level of engagement in common daily activities was also a significant predictor of attention and concentration, even after taking into account variance attributable to education, pain severity, and posttraumatic stress symptoms. Level of general activity moderated the relation between posttraumatic stress symptoms and reasoning ability. This interaction indicated that the expected negative relation between posttraumatic stress symptoms and reasoning ability was significant only among those chronic pain patients who reported low levels of engagement in tasks of daily living. Neither posttraumatic stress symptoms nor


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general activity level predicted significant additional variance in constructional ability over and above that accounted for by education and severity of pain. Although we did not obtain information regarding trauma history of these patients, results suggest that individuals suffering from chronic pain have some characteristics in common with traumatized populations. We defined posttraumatic stress symptoms by scores on the MMPI-2 Pk scale, a measure designed to assess the emotional impact of trauma. The MMPI-2 Pk scores obtained by this sample of chronic pain patients were consistent with the minimum cutoffs accepted for discriminating individuals experiencing symptoms of posttraumatic stress from those who are nonsymptomatic (Norris and Riad, 1997). Furthermore, the association found in the present study between higher levels of posttraumatic stress symptomatology and decreased performance on attention and memory tasks is consistent with results of previous studies that have found that individuals with a history of trauma demonstrate reduced attention and memory functioning in comparison to controls (Dinklage and Grodzinsky, 1993; Uddo et al., 1993). Findings from this study with respect to the relation between general activity level and neurocognitive functioning have many implications for assessment and treatment of individuals with chronic pain. First, results of this study suggest that chronic pain patients who report low levels of general activity are more likely to have difficulties with attention and concentration than those who continue to remain active with respect to their involvement in household chores, recreational and social activities, and activities away from home. The fact that general activity level moderated the relation between posttraumatic stress symptoms and performance on reasoning tasks also suggests that chronic pain patients who report high levels of posttraumatic stress symptoms are more likely than chronic pain patients who report low levels of posttraumatic stress symptoms to demonstrate reasoning deficits if they also report low levels of general activity. Conversely, the lack of a significant relation between posttraumatic stress symptoms and reasoning ability among highly active individuals suggests that maintaining high levels of engagement in tasks of daily living may buffer highly distressed chronic pain patients from reasoning deficits associated with high levels of posttraumatic stress symptomatology. The correlational nature of the study precludes statements regarding causal direction of these relations. However, one implication of these results is that interventions for chronic pain patients who report low levels of activity need to accommodate their difficulties with attention and concentration and reasoning ability. For example, interventions may need to be structured and behaviorally focused. Results also suggest that chronic pain patients may benefit most from interventions delivered early in treatment that help them resume common activities of daily living. This may be particularly true for those chronic pain patients who are highly distressed. This study was not the first to suggest benefits of general activity for chronic pain patients. As indicated by Waddell (1987) in his review of the literature on disability among patients with chronic low-back pain, a number of studies have shown that increased activity is not harmful for these patients, does not necessarily aggravate pain, and appears related to improved physical and mental health. For example, Waddell cited a study by Mayer et al. (1986), which evaluated the impact of an active exercise program that emphasized improved functional capacity rather than pain and also provided psychological support and education focused on managing pain. They found that, in the long-term, these patients had improved functional capacity and lower levels of psychological distress than at the beginning of the


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program. Although those authors did not discuss neurocognitive functioning, our data suggest that those patients might have also demonstrated improved attention and concentration and reasoning ability as a result of that intervention. In addition to restrictions in the ability to make causal interpretations of the data, another limitation of the study is the possibility that the significant relations found between activity level and some of the neurocognitive performance domains reflect the influence of a third variable not included in the model. For example, it is possible that general activity level actually served in this study as a proxy measure of depression. Individuals who reported low levels of activity may have felt more depressed than individuals who reported high levels of activity, and depression may have been the primary cause of their neurocognitive difficulties. The fact that highly distressed chronic pain patients reporting low levels of activity demonstrated the poorest performance on reasoning tasks might therefore indicate the double impact of posttraumatic stress symptoms and depression on this aspect of their neurocognitive functioning. Lack of interview data to support diagnostic classification of the chronic pain patients who participated in this study further prohibited us from distinguishing potential implications of PTSD versus depression for neurocognitive functioning among this population. The relatively small sample size may have also compromised our ability to accurately estimate magnitude of the relations among the variables of interest. In spite of the limitations of this study, these results do indicate a number of possible directions for future research. Future studies need to conduct diagnostic assessments for PTSD and depression to evaluate the influence of PTSD versus depression on neuropsychological functioning. Treatment-evaluation studies examining the impact of increased activity on neurocognitive functioning among individuals with chronic pain are also necessary to support possible causal relations among these variables. ACKNOWLEDGMENTS Support for this study came from the Victoria Hospital Health Services Research Fund Grant 08715. REFERENCES Aiken, L. S., and West, S. G. (1991). Multiple Regression: Testing and Interpreting Interactions, Sage, Newbury Park, CA. Asmundson, G. J., Norton, G. R., Allerdings, M. D., Norton, P. J., and Larsen, D. K. (1998). Posttraumatic stress disorder and work-related injury. J. Anx. Disord. 12: 57–69. Asmundson, G. J., Norton, P. J., and Norton, G. R. (1999). Beyond pain: The role of fear and avoidance in chronicity. Clin. Psychol. Rev. 19: 97–119. Benedikt, R. A., and Kolb, L. C. (1986). Preliminary findings on chronic pain and posttraumatic stress disorder. Am. J. Psychiat. 143: 908–910. Benton, A. L., and Hamsher, K. (1978). Multilingual Aphasia Examination: Manual of Instruction, AJA Associates, Iowa City. Bremner, J. D., Scott, T. M., Delaney, R. C., Southwick, S. M., Mason, J. W., Johnson, D. R., Innis, R. B., McCarthy, G., and Charney, D. S. (1993). Deficits in short-term memory in posttraumatic stress disorder. Am. J. Psychiat. 150: 1015–1019. Butcher, J. N., Dahlstrom, W. G., Graham, J. R., Tellegen, A. M., and Kaemmer, B. (1989). MMPI-2: Minnesota Multiphasic Inventory-2: Manual for Administration and Scoring, University of Minnesota Press, Minneapolis, MN.


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Dinklage, D., and Grodzinsky, G. M. (1993, February). Neuropsychological deficits in severely sexually abused children. Paper presented at the meeting of the International Neuropsychological Society, Galveston, TX. Geisser, M. E., Roth, R. S., Bachman, J. E., and Eckert, T. A. (1996). The relationship between symptoms of posttraumatic stress disorder, affective disturbance and disability among patients with accident and non-accident related pain. Pain 66: 207–214. Golden, D. J. (1978). Stroop Colour Word Test, Stoelting, Chicago. Gronwall, D. M. A., and Sampson, H. (1974). The Psychological Effects of Concussion, Auckland University Press/Oxford University Press, Auckland. Heaton, R. K. (1981). Wisconsin Card Sorting Test Manual, Psychological Assessment Resources, Odessa. Hickling, E. J., and Blanchard, E. B. (1992). Post-traumatic stress disorder and motor vehicle accidents. J. Anx. Disord. 6: 285–291. Hovens, J., and van der Ploeg, M. (1993). Posttraumatic stress disorder in Dutch psychiatric in-patients. J. Traum. Stress 6: 91–102. Iezzi, A., Archibald, Y., Barnett, P., Klinck, A., and Duckworth, M. (1999a). Neurocognitive performance and emotional status in chronic pain patients. J. Behav. Med. 22(3): 205–216. Iezzi, T., Archibald, Y., Duckworth, M. P., and Klinck, A. (1999b, November). Predictors of neurocognitive performance in chronic pain patients. Poster presented at the meeting of the Association for the Advancement of Behavior Therapy, Toronto, Ontario. Jones-Gottman, M., and Milner, B. (1977). Design fluency: The invention of nonsense drawings after focal cortical lesions. Neuropsychology 15: 653–674. Keane, T. M., Malloy, P. F., and Fairbank, J. A. (1984). Empirical development of an MMPI subscale for the assessment of combat-related posttraumatic stress disorder. J. Consult. Clin. Psychol. 52: 888–891. Kerns, R. D., Turk, D. C., and Rudy, T. E. (1985). The West Haven-Yale Multidimensional Pain Inventory (WHYMPI). Pain 23: 345–356. Knight, J. A. (1997). Neuropsychological assessment in posttraumatic stress disorder. (1997). In Wilson, J. P., and Keane, T. M. (eds.), Assessing Psychological Trauma and PTSD Guilford, New York, NY, pp. 448–492. Koretsky, M., and Peck, A. (1990). Validation and crossvalidation of the PTSD subscale of the MMPI with civilian trauma victims. J. Clin. Psychol. 46: 296–300. Kuch, K., Evans, R. E., Watson, P. C., Bubela, C., and Cox, B. J. (1991). Road vehicle accidents and phobias in 60 patients with fibromyalgia. J. Anx. Disord. 5: 273–280. Matthews, C. G., and Klove, H. (1964). Instruction Manual for the Adult Neuropsychology Test Battery, Madison University of Wisconsin Medical School, Madison. Mayer, T. G., Gatchel, R. J., Kishino, N., Keeley, J., Mayer, H., Capra, P., and Mooney, V. (1986). A prospective short-term study of chronic low back pain patients utilizing novel objective functional measurement. Pain 25: 53–68. Melzack, R. (1999). From the gate to the neuromatrix. Pain (Suppl. 6): S121–S126. Norris, F. H., and Riad, J. K. (1997). Standardized self-report measures of civilian trauma and posttraumatic stress disorder. In Wilson, J. P., and Keane, T. M. (eds.), Assessing Psychological Trauma and PTSD, Guilford, New York, NY, pp. 7–42. Norusis, M. J. (1996). SPSS for Windows: Release 7.5, SPSS, Chicago, IL. Osterreith, P. (1944). Le test de copie d’une figure complexe. Archives de Psychologie 30: 206–356. Rey, A. (1941). L’examen psychogique dans les cas d’encephalopathie traumatique. Archives de Psychologie 28: 286–340. Spreen, O., and Benton, A. L. (1965). Comparative studies of some psychological tests for cerebral damage. J. Nerv. Ment. Dis. 140: 323–333. Tabachnick, B. G., and Fidell, L. S. (1996). Using Multivariate Statistics, 3rd Ed., Harper Collins College Publishers, New York. Tartar, R. E., Hegedus, A. M., Winsten, N. E., and Alterman, A. I. (1984). Neuropsychological, personality and familial characteristics of physically abused delinquents. J. Acad. Child Psychiat. 23: 668–674. Uddo, M., Vasterling, J. J., Brailey, K., and Sutker, P. (1993). Memory and attention in combat-related PTSD. J. Psychopathol. Behav. Assess. 15: 43–52. van der Kolk, B. A. (1996). The body keeps the score: Approaches to the psychobiology of posttraumatic stress disorder. In van der Kolk, B. A., McFarlane, A. C., and Weisaeth, L. (eds.), Traumatic Stress: The Effects of Overwhelming Experience on Mind, Body, and Society, Guilford, New York, NY, pp. 214–241. Waddell, G. (1987). A new clinical model for the treatment of low-back pain. Spine 12: 632–644. Wechsler, C. (1981). Wechsler Adult Intelligence Scale-Revised Manual, Psychological Corporation, New York. Wechsler, C. (1987). Wechsler Memory Scale-Revised-Manual, Psychological Corporation, New York. West, S. G., Aiken, L. S., and Krull, J. L. (1996). Experimental personality designs: Analyzing categorical by continuous variable interactions. J. Person. 64: 1–48.