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Negative affect and the experience of chronic pain
Journal of Psychosomatic Research, Vol. 36, No. 8. pp. 707-713, 1992. Printed in Great Britain.
0022 3999/92 $5.00+.00 © 1992 Pergamon Press plc
N E G A T I V E A F F E C T A N D THE EXPERIENCE OF CHRONIC PAIN M. E. GASKIN, A. F. GREENE, M. E. ROBINSON and M. E. GEISSER (Received 12 December 1991; accepted in revised form 10 March 1992)
Abstract--Although it is clear from previous research that pain is associated with negative affect, the relative contribution of specific affective dimensions, e.g. depression, anxiety and anger, to the subjective experience of chronic pain is unclear. The literature is also mixed concerning the relative importance of state versus trait influences in the experience of chronic pain. The present study analyzed the ability of anxiety, anger, and depression (as measured by the State-Trait Personality Inventory, State-Trait Anger Expression Inventory, and the Beck Depression Inventory, respectively) to predict self-report of clinical pain as indicated by the McGill Pain Questionnaire (MPQ) in a sample of 60 chronic pain patients. The results of stepwise regression analyses consistently demonstrated that the state measures were more strongly related to MPQ pain ratings than trait measures. These data suggest support for the hypothesis that chronic pain adversely impacts mood rather than the opposing hypothesis that negative mood is a predisposing factor in the development of chronic pain. Furthermore, different aspects of the state emotional experience were found to be related to different components of pain report. The results of this study also suggest that attributional processes could be an important component of the relationship between negative mood and the experience of pain. INTRODUCTION IN THE study o f the relation between c o g n i t i v e - a f f e c t i v e processes and pain, evidence is g r o w i n g to implicate the role o f negative affect, especially anxiety and depression in the subjective experience of chronic pain [ 1 - 3 ] . E x a m i n i n g the relationship b e t w e e n anxiety and pain over two decades ago, Sternbach [ 4 ] reported that m a n y studies indicate that more anxious persons show greater pain responses. K r e m e r and A t k i n s o n [5] also describe chronic pain populations as having a high incidence of anxiety and depression and as d e m o n s t r a t i n g the disruptive effects o f affective distress on cognitive tasks. Although the role of anxiety and depression in chronic pain has been well documented, empirical studies investigating the role o f anger in the experience of pain are scant. F e u e r s t e i n [6] found higher levels of anxiety, depression, and anger (state measures) in chronic low back pain patients as compared to a s y m p t o m a t i c controls. K i n d e r and Curtiss [7] discussed two studies on a n g e r and pain and concluded that both the experience and expression of anger may be significant factors in chronic pain. In one study they discussed, trait anger functioned as a classic suppressor variable for male pain patients, with trait anger scores (measured by the S t a t e - T r a i t Personality I n v e n t o r y ) e n h a n c i n g the relationship b e t w e e n trait anxiety scores and the M i n n e s o t a Multiphasic Personality I n v e n t o r y ( M M P I ) H y p o c h o n d r i a s i s , Depression, and Hysteria scales. In the second study they described, male and female pain patients were separated into h o m o g e n e o u s subgroups based u p o n a cluster analysis o f M M P I profiles. Significant differences were found b e t w e e n the subgroups on measures o f state anxiety, trait anxiety, and trait anger as well as on measures of Department of Clinical and Health Psychology, University of Florida. Address correspondence to: Anthony F. Greene, Ph.D., Department of Clinical and Health Psychology, Box 100165 Health Science Center, Gainesville, FL 32610, U.S.A. 707
708
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anger expression, Anger-In and Anger-Out. The above studies suggest that both the state and trait dimensions of negative affect may be important in the experience of chronic pain. In a similar study, Robinson et al. [8] examined the relationship of M M P I cluster type to diagnostic category and pain in 485 headache patients. Results of that study indicated that while pain was related to diagnostic category, M M P I cluster groups were not. The authors concluded that the M M P I reflected a patient's coping resources and responses to pain rather than a predisposing personality style. Wade et al. [3 ] investigated the relative contribution of frustration, fear, anger, and anxiety to pain-related unpleasantness and depression in 143 pain patients. The authors found that anxiety, frustration, and anger predicted pain-related unpleasantness and that depression, anxiety, and anger predicted clinical depression. The results of this study lend support to the notion of the 'suffering' component in the experience of chronic pain [9] and demonstrate that several factors may contribute to this experience. Jensen et al. [ 1 ] also demonstrated that the report of pain is associated with a strong affective component. These authors provided reliability and validity data for a Pain Discomfort Scale designed to assess the affective component of pain. This scale correlated significantly with the Affective Pain Rating Index from the McGill Pain Questionnaire (MPQ) but not with the Present Pain Intensity Scale from the MPQ. The authors conclude that their research provides support for a component of pain distinct from pain intensity which involves cognitive aspects, such as attributions or beliefs regarding pain, in addition to the affective pain experience. Although previous research suggests an association between negative affect and pain, the relation of specific affective traits to the reports of pain itself has not been fully articulated. It is clear that pain is associated with negative affect, but the relative contribution of specific affective dimensions to the subjective experience of chronic pain is unclear. The literature is also mixed concerning the relative importance of state versus trait influences in chronic pain. The current study sought to determine the best predictors of the subjective report of clinical pain using assessment instruments with well-established psychometric properties in a sample of chronic pain patients. It was hypothesized that anger, depression, and anxiety would each significantly contribute to the experience of pain. Significant relationships between state measures of negative affect and pain would support the hypothesis that chronic pain has negative effects on mood. Significant relationships between trait measures of negative affect and pain would lend support to hypotheses regarding predisposing personality traits in the development of chronic pain. METHOD
Sl~bjects The participants in this study were 22 male (36.7%) and 38 (63.3%) female subjects recruited from local arthritis and fibromyalgia support groups and from out-patients at an orthopaedic clinic in a tertiary care facility. Subjects were included in the study if they had a history of a chronic pain syndrome of at least 6 months duration and were at least 18 yr old. Ninety-five percent of the subjects experienced pain daily with the remaining 5% experiencing pain several times per month. Other descriptive information is contained in Table I.
Negative affect and pain
709
TABLE I . - - S U B J E C T DESCRIPTIVE INFORMATION
Mean Age Years education Duration of pain (months) Average pain rating (0-10)
45.03 14.95 129.77 4.98
(SD) (14.95) (3.41) (150.18) (2.19)
Primary diagnosis
N
(%)
Back pain Arthritis Fibromyalgia Other
26 16 12 6
(43.3) (26.7) (20.0) (10.0)
Medications
N
(%)
No medications Analgesics Muscle relaxants Narcotics Antidepressants Non-steroidal anti-inflammatory Other
12 10 4 4 6 14 10
(20.0) (16.7) (6.7) (6.7) (10.0) (23.3) (16.7)
Measures Beck Depression Inventory (BDI). The BDI consists of 21 items that assess the cognitive -affective and neurovegetative signs of depression. The BDI has been standardized on psychiatric and nonpsychiatric populations [ 10] with alpha coefficients ranging from 0.73 to 0.95. State-Trait Personality Inventor), (STPI). The STPI [ 11 ] consists of six 10-item subscales that assess state and trait anxiety, anger, and curiosity. The state scales measure the intensity of a subject's feelings at the time of administration. The trait scales assess the frequency with which a subject experiences anxious, angry, or curious feelings. Alpha coefficients for each subscale range from 0.76 to 0.88. Only the state and trait anxiety subscales were used in this study. State-Trait Anger Expression Inventory (STAXI). The STAXI [ 12] consists of 44 items on which subjects rate themselves on four-point scales that assess either the intensity of their angry feelings or the frequency with which anger is experienced, expressed, suppressed or controlled. The STAXI forms six scales and two subscales: State Anger (S-Anger), Trait Anger (T-Anger), Angry Temperament (TAnger/T), Angry Reaction (T-Anger/R), Anger-In (AX/In), Anger-Out (AX/Out), Anger Control (AX/Con), Anger Expression (AX/EX). Alpha coefficients for each subscale rankle from 0.73 to 0.87. The full complement of anger subscales, excluding Temperament and Reaction, were used in this study. McGill Pain Questionnaire (MPQ). The MPQ consists of 20 groups of single word pain descriptors with the words in each group increasing in rank order intensity. The sum of the rank values for each descriptor based on its position in the word set results in a score called the Pain Rating Index (PRI). The MPQ also consists of several subscales: the Sensory PRI, Present Pain Intensity (PPI), and Number of Words Circled. Clinical and experimental data have demonstrated that the MPQ displays acceptable reliability and validity as a method of measuring subjective pain experience [ 13, 14]. Procedures The data described in the present study were part of a larger study described elsewhere [ 15]. After establishing written informed consent, subjects were administered the MPQ, the BDI, the STPI, and the STAXI. Upon completion of these questionnaires, subjects underwent other experimental procedures. Subjects were fully debriefed following all procedures. RESULTS M e a n s and standard deviations for the negative affect variables and the M P Q s u b s c a l e s a r e p r e s e n t e d in T a b l e II. S t e p w i s e m u l t i p l e r e g r e s s i o n s w e r e u s e d to e x a m i n e w h i c h o f the variables had the greatest predictive p o w e r . A B o n f e r r o n i a d j u s t m e n t o f t h e l e v e l o f s i g n i f i c a n c e w a s u s e d to c o n t r o l f o r i n f l a t i o n o f T y p e I e r r o r d u e to t h e m u l t i p l e r e g r e s s i o n a n a l y s e s ( 0 . 0 5 / 7 = 0 . 0 0 7 ) .
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M.E.
G~SKIN et al.
TABLE I I . - - M E A N S AND STANDARD DEVIATIONS FOR NEGATIVE AFFECT AND PAIN VARIABLES
Variable
Mean
sD
BDI
11.43 17.13 20.63 10.87 17.55 15.85 14.38 22.20
(9.77) (5.82) (7.67) (2.51) (4.60) (4.50) (3.57) (7.68)
14.32 2.33 2.12 4.43 23.0 2.15 10.12
(8.21) (2.56) (1.50) (2.95) (12.94) (1.20) (4.58)
State Anxiety Trait Anxiety State Anger Trait Anger Anger In Anger Out Anger Control MPQ
Sensory PRI Affective PRI E v a l u a t i v e PRI
Miscellaneous PRI Total PRI PPI
Number of Words Circled
The negative affect variables were entered into stepwise regressions predicting each o f the subscales of the MPQ (see Table III). Results indicated that state anger and state anxiety were the most important predictors o f Affective PRI scores [R 2 = 0 . 3 8 , F (2,57) = 17.70, p < 0.0001 ] ; that state anxiety was the single most important predictor o f Sensory PRI [R 2 = 0.19, F (1,58) = 13.48, p < 0 . 0 0 1 ] and Miscellaneous PRI [R 2 = 0.26, F (1,58) = 20.36, p < 0.0001 ] ; that depression scores were the single most important predictor o f Present Pain Intensity [R 2 = 0.19, F ( 1 , 5 8 ) = 13.75, p < 0 . 0 0 1 ] and Evaluative PRI [R 2 = 0 . 1 5 , F ( 1 , 5 8 ) = 9.86, p < 0 . 0 0 5 ] ; and that state anxiety and depression scores were the most important predictors o f Number o f Words Circled [R 2 = 0.27, F (2,57) = 10.64, p < 0 . 0 0 0 1 ] and Total PRI [R2=0.33, F (2,57)= 14.22, p < 0 . 0 0 0 1 ] . These data suggest that transient mood was significantly associated with different aspects o f subjective pain report, with higher levels o f negative affect predicting greater subjective pain report in all cases.
TABLE III.--SUMMARIES OF STEPWISE REGRESSION ANALYSIS PREDICTING MCGILL PAIN QUESTIONNAIRE SCORES FROM NEGATIVE AFFECT VARIABLES
Criterion
Predictor
Beta
t
Affective PRI
State Anger State Anxiety State Anxiety State Anxiety Depression Depression State Anxiety Depression State Anxiety Depression
0.44 0.26 0.43 0.51 0.44 0.38 0.36 0.26 0.41 0.28
3.6 2.2 3.7 4.5 3.7 3.1 2.9 2.1 3.4 2.3
Sensory P R I Misc. P R I PPI
Evaluative P R I Number of Words Circled Total P R I
*p < 0 . 0 5 ; **p < 0 . 0 1 ; ***p < 0 . 0 0 1 .
~'With one variable in the equation.
F
R2
28.93?*** 17.70"** 13.50"* 20.36*** 13.75"* 9.9** 15.96?** 10.64"* 21.467"** 14.22"**
0.33+ 0.38 0.19 0.26 0.19 0.15 0.22+ 0.27 0.27t 0.33
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711
DISCUSSION
While the literature has indicated that pain has a definite affective component, the relative contribution of discrete emotions to the pain report of chronic pain patients has not been evaluated. The present study analyzed the ability of anxiety, anger, and depression to predict self-report of pain as indicated by the McGill Pain Questionnaire. The findings suggest that situational mood, as compared to affective traits, was an important determinant of pain reports. Furthermore, different aspects of the state emotional experience were related to different components of pain report. Affective PRI scores were expected to relate highly to self-report of negative affect. State anxiety and anger predicted 38% of the variance in this subscale, indicating that measures of anxiety and anger predicted the affective component of the self-report of pain on the MPQ. These findings are consistent with those of Wade et al. [3] who also found that anxiety and anger were highly related to patients' ratings of pain-related unpleasantness. The results of the present study as well as the relationship between negative affect and the visual analogue ratings of pain unpleasantness used by Wade et al. [3] provide some construct validity for the affective component of the MPQ. Unfortunately, neither of these studies evaluated the causality of these relationships. The Sensory PRI component of the subjects' pain report was best predicted by state anxiety, as was the Miscellaneous PRI set of descriptors from the MPQ. The rating of state anxiety in the current study also significantly predicted the Number of Words Circled and the Total Pain Rating Index, suggesting that the descriptors associated with the measurement of state anxiety were most similar to the language chosen to describe pain. This may reflect an association between the general somatic arousal of anxiety and interpretations of this arousal that fit pain patients' perceptions of the situation. These data suggest that attributional processes could be an important component of the relationship between negative mood and the language chosen to describe pain. Other data in support of an attributional component in the experience of pain are found in the association of depression to pain report. Depression scores were the single most significant predictor of both the Evaluative PRI component and the Present Pain Intensity Rating on the MPQ. Several attributional patterns have been shown to have reliable associations with measures of depression [ 16]. Love [ 17] studied the attributional styles of depressed and nondepressed chronic low back pain patients and found support for an association between depression and attributional style for negative events. Unfortunately, the relationship between depression, attributional style, and pain report was not evaluated. Depression scores also contributed unique variance beyond that accounted for by state anxiety in predicting the Number of Words Circled and the Total Pain Rating Index. This finding is consistent with those of Kremer and Atkinson [5 ] and Wade et al. [3] and validates that negative affect consists of unique dimensions with different contributions to the experience of pain. Overall, the relationships that emerged in the current study support a model of pain that includes a cognitive-affective dimension that is multi-determined with respect to negative affect. This is consistent with the International Association for the Study of Pain definition of pain as 'an unpleasant sensory and emotional experience
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associated with actual or potential tissue damage, or described in terms of such damage, or both' [ 18]. The results of this study are also consistent with recent reports using different measures and methods which confirm that negative affect is an important determinant of the subjective of pain [1, 3]. This is consistent with Merskey's view that: "'Pain is a subjective experience... It has to be defined in terms of psychology and not p h y s i o l o g y . . . All pain has physical correlates, but sometimes they are presumed to be brain events related to thoughts, sometimes they are pathophysiological brain discharges (as in central pain), and sometimes they are brain events related to peripheral changes." [ 19]
The present study extends prior findings by mapping out more clearly how several discrete emotions independently relate to the total experience of pain. The current study also evaluated the relative contribution of state and trait affect to pain ratings in a sample of chronic pain patients. Given the mixture of measures in the literature, it was unclear whether long-term personality features or transient emotional states would be more predictive of pain report. The stepwise analyses allowed determination of whether the state or trait measures, for which there is a relatively high correlation, were the best predictors of pain report. The analyses consistently demonstrated that the state measures were more strongly related to MPQ pain ratings than the trait measures. These data suggest support for the hypothesis that chronic pain adversely impacts mood rather than hypotheses that regard negative mood as a predisposing factor in the development of chronic pain. Although the influence of personality traits on symptom presentation has been suggested in other patient populations [ 2 0 ] , little support for this relationship was found in the present study. Although as a group the subjects in this study may differ from those seen in any one pain clinic, the variety of diagnoses represented encompasses a greater range of the pain experience and enhances the generalizability of these findings. The replication and extension of previous findings in the literature as well as the use of psychometrically sophisticated measures of negative affect and pain report in the present study also offer support for the validity of these findings. The data suggest that future research into the influence of attributional processes and specific dimensions of affect on the experience and report of pain may enable better profiling of psychological interventions in pain management. Specific focus on cognitive treatments for depression, alleviation of anxiety,and/or anger management may be more effective for individual chronic pain patients than a generic pain management program for a given subset of patients. REFERENCES I. JENSEN MP, KAROLY P, HARRIS P. Assessing the affective component of chronic pain: Development of the Pain Discomfort Scale. J Psychosom Res 1991; 35: 149-154. 2. LINTON SJ, GOTESTAM KG. Relations between pain, anxiety, mood and muscle tension in chronic pain patients. Psychother Psychosom 1985; 43: 90-95. 3. WADE JB, PRICE DD, HAMER RM, SCHWARTZ SM, HART RP. An emotional component analysis of chronic pain. Pain 1990; 40: 303--310. 4. STERNBACH RA. Pain: A Psychological Analysis. New York: Academic Press, 1968. 5. KREMER EF, ATKINSONJH JR. Pain language as a measure of affect in chronic pain patients. In Pain Measurement and Assessment (Edited by MELZACK R) pp. 119--127. New York: Raven Press, 1983.
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6. FEUERSTEIN M. Ambulatory monitoring of paraspinal skeletal muscle, autonomic and mood-pain interaction in chronic low back pain. Paper presented at the 7th Annual Meeting of the Society of Behavioral Medicine, San Francisco, 1986. 7. KINDER BN, CURTISS G. Assessment of anxiety, depression, and anger in chronic pain patients: Conceptual and methodological issues. In Advances in Personality Assessment (Edited by SPIELBERGER CD, BUTCHER JN) pp. 161--174. Hillsdale: Lawrence Erlbaum Associates, 1988. 8. ROBINSON ME, GEISSER ME, DIETER JN, SWERDLOW B. The relationship between MMPI cluster membership and diagnostic category in headache patients. Headache 1991 ; 31 (2): 111-115. 9. FORDYCE WE. Pain and suffering. Am Psychol 1988; 43: 2 7 6 - 2 8 3 . 10. BECK AT, STEER RA, GARmN MG. Psychometric properties of the Beck Depression Inventory: Twenty-five years of evaluation. Clin Psychol Rev 1988; 8: 7 7 - 1 0 0 . 11. SPIELBERGER CD, JACOBS G, CRANE R, RUSSELL S, WESTBERRY L, BARKER L, JOHNSON E, KNIGH1 J, MARKS E. Preliminary manual for the State--Trait Personality Inventory (STPI), unpublished manuscript, 1983. 12. SPIELBERGER CD. State-Trait Anger Expression Inventor" Professional Manual. Odessa: Psychological Assessment Resources, Inc., 1988. 13. MELZACK R. The McGill pain questionnaire. In Pain Measurement and Assessment (Edited by MELZACK R) pp. 4 1 - 4 7 . New York: Raven Press, 1985. 14. READING AE. The McGill pain questionnaire. An appraisal. In Pain Measurement and Assessment (Edited by MELZACK R) pp. 55--61. New York: Raven Press, 1985. 15. GASKIN ME. Chronic pain: Evidence of a central processing mechanism? Unpublished master's thesis, University of Florida, Gainesville, FL, 1991. 16. SWEENEY PD, ANDERSON K, BAILEY S. Attributional style in depression: A meta-analytic review. J Person Soc Psychol 1986; 50 (5): 9 7 4 - 9 9 1 . 17. LOVE AW. Attributional style of depressed chronic low back patients. J Clin Psycho/ 1988; 44 (3): 317-321. 18. INTERNA]IONAL ASSOCIATION FOR THE STUDY OF PAIN (SUBCOMMITTEE ON TAXONOMY). Pain terms: A list with definitions and notes on usage. Pain 1979; 6: 2 4 9 - 2 5 2 . 19. MERSKEY H. Psychiatry and pain. In The Psychology of Pain (Edited by STERNBACK RA) pp. 97 120. New York: Raven Press, 1986. 20. COSTA PT JR, FLEG JL, MCCRAE RR, LAKATTA EG. Neuroticism, coronary artery disease and chest pain complaints: Cross-sectional and longitudinal findings. Exper Aging Res 1982; 8: 3 7 - 4 4 .
0022 3999/92 $5.00+.00 © 1992 Pergamon Press plc
N E G A T I V E A F F E C T A N D THE EXPERIENCE OF CHRONIC PAIN M. E. GASKIN, A. F. GREENE, M. E. ROBINSON and M. E. GEISSER (Received 12 December 1991; accepted in revised form 10 March 1992)
Abstract--Although it is clear from previous research that pain is associated with negative affect, the relative contribution of specific affective dimensions, e.g. depression, anxiety and anger, to the subjective experience of chronic pain is unclear. The literature is also mixed concerning the relative importance of state versus trait influences in the experience of chronic pain. The present study analyzed the ability of anxiety, anger, and depression (as measured by the State-Trait Personality Inventory, State-Trait Anger Expression Inventory, and the Beck Depression Inventory, respectively) to predict self-report of clinical pain as indicated by the McGill Pain Questionnaire (MPQ) in a sample of 60 chronic pain patients. The results of stepwise regression analyses consistently demonstrated that the state measures were more strongly related to MPQ pain ratings than trait measures. These data suggest support for the hypothesis that chronic pain adversely impacts mood rather than the opposing hypothesis that negative mood is a predisposing factor in the development of chronic pain. Furthermore, different aspects of the state emotional experience were found to be related to different components of pain report. The results of this study also suggest that attributional processes could be an important component of the relationship between negative mood and the experience of pain. INTRODUCTION IN THE study o f the relation between c o g n i t i v e - a f f e c t i v e processes and pain, evidence is g r o w i n g to implicate the role o f negative affect, especially anxiety and depression in the subjective experience of chronic pain [ 1 - 3 ] . E x a m i n i n g the relationship b e t w e e n anxiety and pain over two decades ago, Sternbach [ 4 ] reported that m a n y studies indicate that more anxious persons show greater pain responses. K r e m e r and A t k i n s o n [5] also describe chronic pain populations as having a high incidence of anxiety and depression and as d e m o n s t r a t i n g the disruptive effects o f affective distress on cognitive tasks. Although the role of anxiety and depression in chronic pain has been well documented, empirical studies investigating the role o f anger in the experience of pain are scant. F e u e r s t e i n [6] found higher levels of anxiety, depression, and anger (state measures) in chronic low back pain patients as compared to a s y m p t o m a t i c controls. K i n d e r and Curtiss [7] discussed two studies on a n g e r and pain and concluded that both the experience and expression of anger may be significant factors in chronic pain. In one study they discussed, trait anger functioned as a classic suppressor variable for male pain patients, with trait anger scores (measured by the S t a t e - T r a i t Personality I n v e n t o r y ) e n h a n c i n g the relationship b e t w e e n trait anxiety scores and the M i n n e s o t a Multiphasic Personality I n v e n t o r y ( M M P I ) H y p o c h o n d r i a s i s , Depression, and Hysteria scales. In the second study they described, male and female pain patients were separated into h o m o g e n e o u s subgroups based u p o n a cluster analysis o f M M P I profiles. Significant differences were found b e t w e e n the subgroups on measures o f state anxiety, trait anxiety, and trait anger as well as on measures of Department of Clinical and Health Psychology, University of Florida. Address correspondence to: Anthony F. Greene, Ph.D., Department of Clinical and Health Psychology, Box 100165 Health Science Center, Gainesville, FL 32610, U.S.A. 707
708
M . E . GASKIN et al.
anger expression, Anger-In and Anger-Out. The above studies suggest that both the state and trait dimensions of negative affect may be important in the experience of chronic pain. In a similar study, Robinson et al. [8] examined the relationship of M M P I cluster type to diagnostic category and pain in 485 headache patients. Results of that study indicated that while pain was related to diagnostic category, M M P I cluster groups were not. The authors concluded that the M M P I reflected a patient's coping resources and responses to pain rather than a predisposing personality style. Wade et al. [3 ] investigated the relative contribution of frustration, fear, anger, and anxiety to pain-related unpleasantness and depression in 143 pain patients. The authors found that anxiety, frustration, and anger predicted pain-related unpleasantness and that depression, anxiety, and anger predicted clinical depression. The results of this study lend support to the notion of the 'suffering' component in the experience of chronic pain [9] and demonstrate that several factors may contribute to this experience. Jensen et al. [ 1 ] also demonstrated that the report of pain is associated with a strong affective component. These authors provided reliability and validity data for a Pain Discomfort Scale designed to assess the affective component of pain. This scale correlated significantly with the Affective Pain Rating Index from the McGill Pain Questionnaire (MPQ) but not with the Present Pain Intensity Scale from the MPQ. The authors conclude that their research provides support for a component of pain distinct from pain intensity which involves cognitive aspects, such as attributions or beliefs regarding pain, in addition to the affective pain experience. Although previous research suggests an association between negative affect and pain, the relation of specific affective traits to the reports of pain itself has not been fully articulated. It is clear that pain is associated with negative affect, but the relative contribution of specific affective dimensions to the subjective experience of chronic pain is unclear. The literature is also mixed concerning the relative importance of state versus trait influences in chronic pain. The current study sought to determine the best predictors of the subjective report of clinical pain using assessment instruments with well-established psychometric properties in a sample of chronic pain patients. It was hypothesized that anger, depression, and anxiety would each significantly contribute to the experience of pain. Significant relationships between state measures of negative affect and pain would support the hypothesis that chronic pain has negative effects on mood. Significant relationships between trait measures of negative affect and pain would lend support to hypotheses regarding predisposing personality traits in the development of chronic pain. METHOD
Sl~bjects The participants in this study were 22 male (36.7%) and 38 (63.3%) female subjects recruited from local arthritis and fibromyalgia support groups and from out-patients at an orthopaedic clinic in a tertiary care facility. Subjects were included in the study if they had a history of a chronic pain syndrome of at least 6 months duration and were at least 18 yr old. Ninety-five percent of the subjects experienced pain daily with the remaining 5% experiencing pain several times per month. Other descriptive information is contained in Table I.
Negative affect and pain
709
TABLE I . - - S U B J E C T DESCRIPTIVE INFORMATION
Mean Age Years education Duration of pain (months) Average pain rating (0-10)
45.03 14.95 129.77 4.98
(SD) (14.95) (3.41) (150.18) (2.19)
Primary diagnosis
N
(%)
Back pain Arthritis Fibromyalgia Other
26 16 12 6
(43.3) (26.7) (20.0) (10.0)
Medications
N
(%)
No medications Analgesics Muscle relaxants Narcotics Antidepressants Non-steroidal anti-inflammatory Other
12 10 4 4 6 14 10
(20.0) (16.7) (6.7) (6.7) (10.0) (23.3) (16.7)
Measures Beck Depression Inventory (BDI). The BDI consists of 21 items that assess the cognitive -affective and neurovegetative signs of depression. The BDI has been standardized on psychiatric and nonpsychiatric populations [ 10] with alpha coefficients ranging from 0.73 to 0.95. State-Trait Personality Inventor), (STPI). The STPI [ 11 ] consists of six 10-item subscales that assess state and trait anxiety, anger, and curiosity. The state scales measure the intensity of a subject's feelings at the time of administration. The trait scales assess the frequency with which a subject experiences anxious, angry, or curious feelings. Alpha coefficients for each subscale range from 0.76 to 0.88. Only the state and trait anxiety subscales were used in this study. State-Trait Anger Expression Inventory (STAXI). The STAXI [ 12] consists of 44 items on which subjects rate themselves on four-point scales that assess either the intensity of their angry feelings or the frequency with which anger is experienced, expressed, suppressed or controlled. The STAXI forms six scales and two subscales: State Anger (S-Anger), Trait Anger (T-Anger), Angry Temperament (TAnger/T), Angry Reaction (T-Anger/R), Anger-In (AX/In), Anger-Out (AX/Out), Anger Control (AX/Con), Anger Expression (AX/EX). Alpha coefficients for each subscale rankle from 0.73 to 0.87. The full complement of anger subscales, excluding Temperament and Reaction, were used in this study. McGill Pain Questionnaire (MPQ). The MPQ consists of 20 groups of single word pain descriptors with the words in each group increasing in rank order intensity. The sum of the rank values for each descriptor based on its position in the word set results in a score called the Pain Rating Index (PRI). The MPQ also consists of several subscales: the Sensory PRI, Present Pain Intensity (PPI), and Number of Words Circled. Clinical and experimental data have demonstrated that the MPQ displays acceptable reliability and validity as a method of measuring subjective pain experience [ 13, 14]. Procedures The data described in the present study were part of a larger study described elsewhere [ 15]. After establishing written informed consent, subjects were administered the MPQ, the BDI, the STPI, and the STAXI. Upon completion of these questionnaires, subjects underwent other experimental procedures. Subjects were fully debriefed following all procedures. RESULTS M e a n s and standard deviations for the negative affect variables and the M P Q s u b s c a l e s a r e p r e s e n t e d in T a b l e II. S t e p w i s e m u l t i p l e r e g r e s s i o n s w e r e u s e d to e x a m i n e w h i c h o f the variables had the greatest predictive p o w e r . A B o n f e r r o n i a d j u s t m e n t o f t h e l e v e l o f s i g n i f i c a n c e w a s u s e d to c o n t r o l f o r i n f l a t i o n o f T y p e I e r r o r d u e to t h e m u l t i p l e r e g r e s s i o n a n a l y s e s ( 0 . 0 5 / 7 = 0 . 0 0 7 ) .
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TABLE I I . - - M E A N S AND STANDARD DEVIATIONS FOR NEGATIVE AFFECT AND PAIN VARIABLES
Variable
Mean
sD
BDI
11.43 17.13 20.63 10.87 17.55 15.85 14.38 22.20
(9.77) (5.82) (7.67) (2.51) (4.60) (4.50) (3.57) (7.68)
14.32 2.33 2.12 4.43 23.0 2.15 10.12
(8.21) (2.56) (1.50) (2.95) (12.94) (1.20) (4.58)
State Anxiety Trait Anxiety State Anger Trait Anger Anger In Anger Out Anger Control MPQ
Sensory PRI Affective PRI E v a l u a t i v e PRI
Miscellaneous PRI Total PRI PPI
Number of Words Circled
The negative affect variables were entered into stepwise regressions predicting each o f the subscales of the MPQ (see Table III). Results indicated that state anger and state anxiety were the most important predictors o f Affective PRI scores [R 2 = 0 . 3 8 , F (2,57) = 17.70, p < 0.0001 ] ; that state anxiety was the single most important predictor o f Sensory PRI [R 2 = 0.19, F (1,58) = 13.48, p < 0 . 0 0 1 ] and Miscellaneous PRI [R 2 = 0.26, F (1,58) = 20.36, p < 0.0001 ] ; that depression scores were the single most important predictor o f Present Pain Intensity [R 2 = 0.19, F ( 1 , 5 8 ) = 13.75, p < 0 . 0 0 1 ] and Evaluative PRI [R 2 = 0 . 1 5 , F ( 1 , 5 8 ) = 9.86, p < 0 . 0 0 5 ] ; and that state anxiety and depression scores were the most important predictors o f Number o f Words Circled [R 2 = 0.27, F (2,57) = 10.64, p < 0 . 0 0 0 1 ] and Total PRI [R2=0.33, F (2,57)= 14.22, p < 0 . 0 0 0 1 ] . These data suggest that transient mood was significantly associated with different aspects o f subjective pain report, with higher levels o f negative affect predicting greater subjective pain report in all cases.
TABLE III.--SUMMARIES OF STEPWISE REGRESSION ANALYSIS PREDICTING MCGILL PAIN QUESTIONNAIRE SCORES FROM NEGATIVE AFFECT VARIABLES
Criterion
Predictor
Beta
t
Affective PRI
State Anger State Anxiety State Anxiety State Anxiety Depression Depression State Anxiety Depression State Anxiety Depression
0.44 0.26 0.43 0.51 0.44 0.38 0.36 0.26 0.41 0.28
3.6 2.2 3.7 4.5 3.7 3.1 2.9 2.1 3.4 2.3
Sensory P R I Misc. P R I PPI
Evaluative P R I Number of Words Circled Total P R I
*p < 0 . 0 5 ; **p < 0 . 0 1 ; ***p < 0 . 0 0 1 .
~'With one variable in the equation.
F
R2
28.93?*** 17.70"** 13.50"* 20.36*** 13.75"* 9.9** 15.96?** 10.64"* 21.467"** 14.22"**
0.33+ 0.38 0.19 0.26 0.19 0.15 0.22+ 0.27 0.27t 0.33
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DISCUSSION
While the literature has indicated that pain has a definite affective component, the relative contribution of discrete emotions to the pain report of chronic pain patients has not been evaluated. The present study analyzed the ability of anxiety, anger, and depression to predict self-report of pain as indicated by the McGill Pain Questionnaire. The findings suggest that situational mood, as compared to affective traits, was an important determinant of pain reports. Furthermore, different aspects of the state emotional experience were related to different components of pain report. Affective PRI scores were expected to relate highly to self-report of negative affect. State anxiety and anger predicted 38% of the variance in this subscale, indicating that measures of anxiety and anger predicted the affective component of the self-report of pain on the MPQ. These findings are consistent with those of Wade et al. [3] who also found that anxiety and anger were highly related to patients' ratings of pain-related unpleasantness. The results of the present study as well as the relationship between negative affect and the visual analogue ratings of pain unpleasantness used by Wade et al. [3] provide some construct validity for the affective component of the MPQ. Unfortunately, neither of these studies evaluated the causality of these relationships. The Sensory PRI component of the subjects' pain report was best predicted by state anxiety, as was the Miscellaneous PRI set of descriptors from the MPQ. The rating of state anxiety in the current study also significantly predicted the Number of Words Circled and the Total Pain Rating Index, suggesting that the descriptors associated with the measurement of state anxiety were most similar to the language chosen to describe pain. This may reflect an association between the general somatic arousal of anxiety and interpretations of this arousal that fit pain patients' perceptions of the situation. These data suggest that attributional processes could be an important component of the relationship between negative mood and the language chosen to describe pain. Other data in support of an attributional component in the experience of pain are found in the association of depression to pain report. Depression scores were the single most significant predictor of both the Evaluative PRI component and the Present Pain Intensity Rating on the MPQ. Several attributional patterns have been shown to have reliable associations with measures of depression [ 16]. Love [ 17] studied the attributional styles of depressed and nondepressed chronic low back pain patients and found support for an association between depression and attributional style for negative events. Unfortunately, the relationship between depression, attributional style, and pain report was not evaluated. Depression scores also contributed unique variance beyond that accounted for by state anxiety in predicting the Number of Words Circled and the Total Pain Rating Index. This finding is consistent with those of Kremer and Atkinson [5 ] and Wade et al. [3] and validates that negative affect consists of unique dimensions with different contributions to the experience of pain. Overall, the relationships that emerged in the current study support a model of pain that includes a cognitive-affective dimension that is multi-determined with respect to negative affect. This is consistent with the International Association for the Study of Pain definition of pain as 'an unpleasant sensory and emotional experience
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associated with actual or potential tissue damage, or described in terms of such damage, or both' [ 18]. The results of this study are also consistent with recent reports using different measures and methods which confirm that negative affect is an important determinant of the subjective of pain [1, 3]. This is consistent with Merskey's view that: "'Pain is a subjective experience... It has to be defined in terms of psychology and not p h y s i o l o g y . . . All pain has physical correlates, but sometimes they are presumed to be brain events related to thoughts, sometimes they are pathophysiological brain discharges (as in central pain), and sometimes they are brain events related to peripheral changes." [ 19]
The present study extends prior findings by mapping out more clearly how several discrete emotions independently relate to the total experience of pain. The current study also evaluated the relative contribution of state and trait affect to pain ratings in a sample of chronic pain patients. Given the mixture of measures in the literature, it was unclear whether long-term personality features or transient emotional states would be more predictive of pain report. The stepwise analyses allowed determination of whether the state or trait measures, for which there is a relatively high correlation, were the best predictors of pain report. The analyses consistently demonstrated that the state measures were more strongly related to MPQ pain ratings than the trait measures. These data suggest support for the hypothesis that chronic pain adversely impacts mood rather than hypotheses that regard negative mood as a predisposing factor in the development of chronic pain. Although the influence of personality traits on symptom presentation has been suggested in other patient populations [ 2 0 ] , little support for this relationship was found in the present study. Although as a group the subjects in this study may differ from those seen in any one pain clinic, the variety of diagnoses represented encompasses a greater range of the pain experience and enhances the generalizability of these findings. The replication and extension of previous findings in the literature as well as the use of psychometrically sophisticated measures of negative affect and pain report in the present study also offer support for the validity of these findings. The data suggest that future research into the influence of attributional processes and specific dimensions of affect on the experience and report of pain may enable better profiling of psychological interventions in pain management. Specific focus on cognitive treatments for depression, alleviation of anxiety,and/or anger management may be more effective for individual chronic pain patients than a generic pain management program for a given subset of patients. REFERENCES I. JENSEN MP, KAROLY P, HARRIS P. Assessing the affective component of chronic pain: Development of the Pain Discomfort Scale. J Psychosom Res 1991; 35: 149-154. 2. LINTON SJ, GOTESTAM KG. Relations between pain, anxiety, mood and muscle tension in chronic pain patients. Psychother Psychosom 1985; 43: 90-95. 3. WADE JB, PRICE DD, HAMER RM, SCHWARTZ SM, HART RP. An emotional component analysis of chronic pain. Pain 1990; 40: 303--310. 4. STERNBACH RA. Pain: A Psychological Analysis. New York: Academic Press, 1968. 5. KREMER EF, ATKINSONJH JR. Pain language as a measure of affect in chronic pain patients. In Pain Measurement and Assessment (Edited by MELZACK R) pp. 119--127. New York: Raven Press, 1983.
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6. FEUERSTEIN M. Ambulatory monitoring of paraspinal skeletal muscle, autonomic and mood-pain interaction in chronic low back pain. Paper presented at the 7th Annual Meeting of the Society of Behavioral Medicine, San Francisco, 1986. 7. KINDER BN, CURTISS G. Assessment of anxiety, depression, and anger in chronic pain patients: Conceptual and methodological issues. In Advances in Personality Assessment (Edited by SPIELBERGER CD, BUTCHER JN) pp. 161--174. Hillsdale: Lawrence Erlbaum Associates, 1988. 8. ROBINSON ME, GEISSER ME, DIETER JN, SWERDLOW B. The relationship between MMPI cluster membership and diagnostic category in headache patients. Headache 1991 ; 31 (2): 111-115. 9. FORDYCE WE. Pain and suffering. Am Psychol 1988; 43: 2 7 6 - 2 8 3 . 10. BECK AT, STEER RA, GARmN MG. Psychometric properties of the Beck Depression Inventory: Twenty-five years of evaluation. Clin Psychol Rev 1988; 8: 7 7 - 1 0 0 . 11. SPIELBERGER CD, JACOBS G, CRANE R, RUSSELL S, WESTBERRY L, BARKER L, JOHNSON E, KNIGH1 J, MARKS E. Preliminary manual for the State--Trait Personality Inventory (STPI), unpublished manuscript, 1983. 12. SPIELBERGER CD. State-Trait Anger Expression Inventor" Professional Manual. Odessa: Psychological Assessment Resources, Inc., 1988. 13. MELZACK R. The McGill pain questionnaire. In Pain Measurement and Assessment (Edited by MELZACK R) pp. 4 1 - 4 7 . New York: Raven Press, 1985. 14. READING AE. The McGill pain questionnaire. An appraisal. In Pain Measurement and Assessment (Edited by MELZACK R) pp. 55--61. New York: Raven Press, 1985. 15. GASKIN ME. Chronic pain: Evidence of a central processing mechanism? Unpublished master's thesis, University of Florida, Gainesville, FL, 1991. 16. SWEENEY PD, ANDERSON K, BAILEY S. Attributional style in depression: A meta-analytic review. J Person Soc Psychol 1986; 50 (5): 9 7 4 - 9 9 1 . 17. LOVE AW. Attributional style of depressed chronic low back patients. J Clin Psycho/ 1988; 44 (3): 317-321. 18. INTERNA]IONAL ASSOCIATION FOR THE STUDY OF PAIN (SUBCOMMITTEE ON TAXONOMY). Pain terms: A list with definitions and notes on usage. Pain 1979; 6: 2 4 9 - 2 5 2 . 19. MERSKEY H. Psychiatry and pain. In The Psychology of Pain (Edited by STERNBACK RA) pp. 97 120. New York: Raven Press, 1986. 20. COSTA PT JR, FLEG JL, MCCRAE RR, LAKATTA EG. Neuroticism, coronary artery disease and chest pain complaints: Cross-sectional and longitudinal findings. Exper Aging Res 1982; 8: 3 7 - 4 4 .