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Pain Location and Psychological Characteristics of Patients With Chronic Pain
Pain Location and Psychological Characteristics of Patients With Chronic Pain ROBERT J. GREGORY, M.D. JOHN MANRING, M.D. SARAH L. BERRY, B.S.
The authors assessed psychological characteristics of 140 medical outpatients with chronic nonmalignant pain referred for psychiatric consultation. Subjects completed the Toronto Alexithymia Scale, Somatosensory Amplification Scale (SSAS), and Counterdependency Scale (CDS). The only psychological measure able to differentiate the chronic pain group from the control subjects was the CDS. However, SSAS scores were significantly higher in subjects having pain involving the head, chest, abdomen, or pelvis than in subjects having pain only in their backs or extremities. The latter subgroup had significantly higher CDS scores. The findings suggest that there are discrete subgroups within the chronic pain population defined by pain location and specific psychological characteristics. (Psychosomatics 2000; 41:216–220)
D
espite extensive writing and research in this area, there is no consensus regarding the psychological characteristics of patients having chronic benign pain. It was formerly believed that pain fulfilled unconscious needs for guilt or masochism1,2 or served as a release for emotional pain.3 More rigorous studies in the 1970s focused on the application of the Minnesota Multiphasic Personality Inventory (MMPI) and the discovery of the “Conversion V” MMPI profile, [i.e., elevation of the hypochondriasis (Hy) and hysteria (Hs) scales with a lesser elevation of the depression (D) scale]. This pattern differentiated chronic pain patients from patients having acute pain,4 but correlations with treatment outcome have been mixed.5 Evidence that the Conversion V profile represents a nonspecific reaction to illness6 and that the Hy and Hs scales are largely somatic checklists have limited the Conversion V’s application and relevance. More recently, focus has shifted to behavioral and cogReceived June 3, 1999; revised August 24, 1999; accepted September 29, 1999. From the Department of Psychiatry, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210. Address reprint requests to Dr. Gregory. Copyright 䉷 2000 The Academy of Psychosomatic Medicine.
216
nitive aspects of chronic pain, such as helplessness, pessimism, and catastrophic fears.7,8 The concept of somatosensory amplification9 has been applied to the chronic pain population to explain how maladaptive cognitions may lead to heightened pain perception.10 Initial studies indicate that in chronic pain populations, somatosensory amplification may be more determined by levels of anxiety and depression than pain per se.11,12 Another development has been the application of the concept of alexithymia to chronic pain. As first described by Sifneos in 1972,13,14 alexithymic traits include difficulties identifying and describing feelings, impoverishment of fantasy life, and excessive preoccupation with physical symptoms and external events. Alexithymia was initially attributed to patients with psychosomatic illnesses,15 but alexithymia has also been reported in patients having posttraumatic stress disorder, eating disorders, panic disorder, and substance use disorders.16 Attempts to apply the alexithymic construct to chronic pain populations have produced mixed results, perhaps because of the confounding effects of psychiatric comorbidity.11,17,18 A need was identified for a psychological marker more specifically associated with chronic pain.11 Psychosomatics 41:3, May-June 2000
Gregory et al. Gregory and Berry19 recently reviewed clinical vignettes of chronic pain patients in past literature to elaborate the concept of counterdependency. Counterdependent patients are characterized by emotional suppression, idealization of relationships, strong work ethic, caregiving role identity, and self-reliance. As part of their study, Gregory and Berry validated a scale to describe these characteristics (Counterdependency Scale). Counterdependency traits were strongly associated with chronic pain and appeared independent of anxiety, depression, or psychiatric comorbidity. In the present study, the authors employ measures of somatosensory amplification, alexithymia, and counterdependency in a large chronic pain population in order to address two questions. Which psychological marker best characterizes patients with chronic pain? Are there discrete subgroups within the chronic pain population differentiated by specific psychological characteristics? METHODS Subjects The study population included 220 consecutive patients referred in 1998 to the Outpatient Psychiatry Consultation Program within the SUNY Health Science Center. Sources of referral included a general medicine clinic (n⳱107), primary care physicians in the community (n⳱74), and a pain treatment center (n⳱39). Patients suffering from chronic nonmalignant pain (n⳱140), which is defined as daily pain over the previous 6 months, were compared with 80 patients without pain. Patients having a primary psychotic disorder, cognitive impairment, or inability to complete questionnaires were excluded from the study. The chronic pain subjects were largely unmarried (n⳱79), White (n⳱121), and female (n⳱105). The subjects had a meansⳲstandard deviation (SD) age of 44.7Ⳳ11.2 years and an educational attainment of 12.3Ⳳ2.4 years. Fifty-one subjects reported a history of sexual or physical abuse in childhood. The control group did not significantly differ in any of these characteristics. One hundred and fourteen subjects had pain involving the back and/or extremities, of whom 65 subjects had pain exclusively in these regions. Other pain locations included head (n⳱45), abdomen (n⳱25), chest (n⳱22), and pelvis (n⳱14). Fifty-one subjects had pain in more than one of these locations. Mean duration of pain was 7.6Ⳳ6.9 years. The subjects were characterized by multiple pain diagnoses Psychosomatics 41:3, May-June 2000
and attributions, often with poorly defined etiological mechanisms. Measures DSM-IV diagnoses and social, developmental, and occupational histories were obtained in semistructured clinical interviews by board-certified psychiatrists (RG and JM). We devised an interview format to prompt the psychiatrist to obtain important parts of the patient’s history, such as childhood sexual or physical abuse, thereby ensuring that all relevant information was gathered. Because of the inherent ambiguity in differentiating organic from functional pain, patients were assigned a pain disorder diagnosis if they reported a clear exacerbation of their pain with emotional stress. Patients referred to the program were also administered a series of questionnaires before each interview, including anxiety and depression subscales of the Brief Symptom Inventory (BSI), the Twenty-Item Toronto Alexithymia Scale (TAS-20), the Somatosensory Amplification Scale (SSAS), and the Counterdependency Scale (CDS). The BSI is a symptom checklist derived from the Hopkins Symptom Checklist and has been shown to have good validity and reliability.20 The Toronto Alexithymia Scale and its two modified versions, the TAS-R and TAS-20, are currently the most commonly used and best researched measures of alexithymia.21,22 Somatic amplification refers to a tendency in hypochondriacal patients to scrutinize their bodies for somatosensory input and then amplify and misinterpret the sensation as representing a pathological process.9 The SSAS was designed and validated to measure this concept.23 The CDS is a 5-item scale developed by Gregory and Berry19 after clinical observations that a large subgroup of chronic pain patients did not follow patterns frequently cited in the literature of dependency, neediness, and depression.1–3 Indeed, these patients appeared to minimize emotional distress; describe idealized, shallow relationships with stereotyped roles; and lead overly productive lives until the development of their pain syndrome. Data Analysis Upon approval from our Institutional Review Board, data from interviews and questionnaires were entered into a computer software program for analysis (STATISTICA, Tulsa, Oklahoma). Between-group differences were assessed by independent t-tests for parametric variables and 217
Chronic Pain Pearson chi square for nonparametric variables. Logistic and stepwise regression analyses were employed to assess the determinants of pain location in our sample. To correct for bias inherent in multiple statistical comparisons, a probability value of 0.01 or less was chosen as representing statistical significance. RESULTS Table 1 outlines the common psychiatric diagnostic categories seen in both groups. Mood disorders represent the largest diagnostic category with major depressive disorder diagnosed in 70 (50%) of the subjects with chronic pain and 37 (46%) of the control subjects. Pain disorder was diagnosed in 45 (32%) of the subjects with chronic pain and other somatoform disorders were diagnosed in 25 (18%) (i.e., half the chronic pain sample was diagnosed with a somatoform disorder). Table 2 compares the psychological measures of the two groups. Only CDS scores differentiated the chronic pain subjects from the control subjects. This difference remained significant in an analysis of covariance (ANCOVA) after controlling for differences in rates of personality disorders between the two groups (F⳱37.2, P⳱0.000). Employing Pearson product-moment correlations, CDS scores were not significantly associated with the other psychological measures or diagnostic categories. Table 3 employs the same psychological measures to contrast two subgroups within the chronic pain sample. TABLE 1.
DSM-IV diagnostic categories of 140 subjects with chronic pain compared with 80 subjects in a control group N(%)
Mood disorders Yes No Anxiety disorders Yes No Substance use disorders Yes No Personality disorders* Yes No
Pain (nⴔ140)
Control (nⴔ80)
91 (65) 49 (35)
54 (67) 26 (33)
31 (22) 109 (78)
21 (26) 59 (74)
20 (14) 120 (86)
16 (20) 64 (80)
19 (14) 121 (86)
23 (29) 57 (71)
*Significant difference (Pearson chi-square: v2⳱7.59; df⳱1; P⳱0.006)
218
Subjects having chronic pain only in their back and/or extremities had significantly higher CDS scores than subjects having chronic pain that included other locations (i.e., head, chest, abdomen, or pelvis). In contrast, the latter group had significantly higher SSAS scores. BSI anxiety scores were also higher in this group but did not quite reach statistical significance (t⳱2.37, df⳱138, P⳱0.019). The duration of pain and the frequency of pain disorder diagnosis did not significantly differ between the two groups, but the group of subjects having pain involving the head, chest, abdomen, or pelvis was more likely to have other somatoform diagnoses (v2⳱18.1, df⳱1, P⳱0.000). Although not quite reaching a P⳱0.01 level of statistical
TABLE 2.
Psychological measures in 140 subjects with chronic pain compared with 80 subjects in a control group MeansⴣSD
BSI anxiety BSI depression SSAS TAS-20 CDS*
Pain Group (nⴔ140)
Control Group (nⴔ80)
1.76Ⳳ1.17 1.65Ⳳ1.22 1.81Ⳳ0.823 53.5Ⳳ16.4 2.75Ⳳ0.761
1.62Ⳳ0.964 1.53Ⳳ1.09 1.65Ⳳ0.687 52.7Ⳳ14.6 2.07Ⳳ0.703
Note: BSI⳱Brief Symptom Inventory; SSAS⳱Somatosensory Amplification Scale; TAS-20⳱Toronto Alexithymia Scale; CDS⳱Counterdependency Scale. *Significant difference (unpaired t-test: t⳱6.58, df⳱218, P⳱0.000).
TABLE 3.
Psychological measures in 65 subjects with chronic pain exclusively in the back and/or extremities compared with 75 subjects with chronic pain involving the head, abdomen, pelvis, and/or chest MeansⴣSD
BSI anxiety BSI depression SSAS* TAS-20 CDS**
Back Extremities Group (nⴔ65)
Other Pain Location Group (nⴔ75)
1.51Ⳳ1.16 1.46Ⳳ1.17 1.48Ⳳ0.733 51.4Ⳳ15.5 2.93Ⳳ0.692
1.97Ⳳ1.15 1.81Ⳳ1.25 2.09Ⳳ0.795 55.3Ⳳ17.1 2.59Ⳳ0.787
Note: BSI⳱Brief Symptom Inventory; SSAS⳱Somatosensory Amplification Scale; TAS-20⳱Toronto Alexithymia Scale; CDS⳱Counterdependency Scale. *Significant difference (unpaired t test: t⳱-4.70, df⳱138, P⳱0.000). ** Significant difference (unpaired t-test: t⳱2.67, df⳱138, P⳱0.008).
Psychosomatics 41:3, May-June 2000
Gregory et al. significance, subjects in this group were also more likely to have anxiety disorders (v2 ⳱4.84, df⳱1,P⳱0.028) and to be unmarried (v2⳱5.21, df⳱ 1, P⳱0.023). The two groups did not significantly differ on other demographic and diagnostic parameters. Psychological measures including SSAS and CDS accounted for 17% of the variance in pain location employing stepwise regression analyses. When a somatoform diagnosis (excluding pain disorder) was added to the equation, the combined variables predicted 26% of the variance in pain location. The addition of anxiety disorder and marital status to the regression equation did not appreciably contribute to the variance, indicating that these variables are not independent predictors of pain location. DISCUSSION An important finding from this study is that counterdependency is the best psychological characteristic to differentiate psychiatric consult patients who have chronic pain from those without pain. Although previous studies have indicated that alexithymia also characterizes some chronic pain populations,12,17 there is evidence that the alexithymia is more a function of comorbid psychopathology than chronic pain per se.11,18,24 Given that our control group had roughly the same rates of psychiatric disorders as our study group, it is perhaps not surprising that TAS-20 scores did not differ substantially between them. The finding of high CDS scores in a chronic pain population is consistent with a previous study validating the scale.19 CDS scores are independent of scores of other measured psychological variables and independent of comorbid psychiatric diagnoses. There are many possible ex-
planations for the observed association between chronic pain and counterdependency traits. The one that best fits the authors’ clinical observations is that self-reliant and hard-working individuals who minimize distress are less likely to seek rest and medical attention after an acute injury, thereby increasing their chances for developing a chronic condition. A more detailed analysis of the data from our study revealed that counterdependency traits were unevenly distributed among different pain locations. Subjects with pain exclusively in the back and/or extremities were likely to have strong counterdependency traits. Subjects having pain involving the head, chest, abdomen, or pelvis were more likely to have anxiety, somatic amplification, and a somatoform disorder (excluding pain disorder). Psychological measures accounted for a large proportion of the variance in pain location. To our knowledge the present study marks the first time that distinct subgroups within a chronic pain population have been identified on the basis of psychological characteristics. If confirmed, this finding would have important implications for treatment and prevention programs. An important bias in our study is that all subjects were referred for psychiatric consultation, thereby preselecting a population having high rates of psychopathology. It is also possible that the differences in psychological characteristics between subgroups were because of factors that we did not measure, such as pain intensity or functional impairment. Further studies are needed to clarify the relationship between counterdependency and chronic pain (i.e., whether the relationship is causal and in which direction). Studies evaluating treatment interventions in chronic pain populations should take into account pain locations and psychological characteristics of their samples.
References
1. Engel GL: “Psychogenic” pain and the pain-prone patient. Am J Med 1959; 26:899–918 2. Rosenbaum JF: Comments on “chronic pain as a variant of depressive disease: the pain-prone disorder.” J Nerv Ment Dis 1982; 170:412–414 3. Dorsel TN: Chronic pain behavior pattern: a simple theoretical framework for health-care providers. Psychol Rep 1989; 65:783– 786 4. Phillips EL: Some psychological characteristics associated with orthopaedic complaints. Curr Pract Orthop Surg 1964; 2:165–176 5. Trief PM, Yuan HA: The use of the MMPI in a chronic back pain rehabilitation program. J Clin Psychol 1983; 39:46–53 6. Sternbach RA, Timmermans G: Personality changes associated with reduction in pain. Pain 1975; 1:177–181 7. Novy DM, Nelson DV, Francis DJ, et al: Perspectives of chronic pain: an evaluative comparison of restrictive and comprehensive models. Psychol Bull 1995; 118:238–247
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8. Miller L: Psychotherapeutic approaches to chronic pain. Psychotherapy 1993; 30:115–123 9. Barsky AJ, Goodson JD, Lane RS, et al: The amplification of somatic symptoms. Psychosom Med 1988; 50:510–519 10. Feuerstein M, Beattie P: Biobehavioral factors affecting pain and disability in low back pain: mechanisms and assessment. Phys Ther 1995; 75:267–280 11. Kosturek A, Gregory RJ, Sousou AJ, et al: Alexithymia and somatic amplification in chronic pain. Psychosomatics 1998; 39:399– 404 12. Lumley MA, Asselin LA, Norman S: Alexithymia in chronic pain patients. Compr Psychiatry 1997; 38:160–165 13. Sifneos PE: Short-Term Psychotherapy and Emotional Crisis. Cambridge, MA, Harvard University Press, 1972 14. Sifneos PE: The prevalence of alexithymia characteristics in psychosomatic patients. Psychother Psychosom 1973; 22:255–262
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Chronic Pain 15. Nemiah JC, Sifneos PE: Affect and fantasy in patients with psychosomatic disorders, in Modern Trends in Psychosomatic Medicine, Vol 2, edited by Hill OW. London, Butterworths, 1970, pp 26–34 16. Sifneos PE: Alexithymia and its relationship to hemisphere specialization, affect, and creativity. Psychiatr Clin North Am 1988; 11:338–353 17. Cox BJ, Kuch K, Parker JDA, et al: Alexithymia in somatoform disorder patients with chronic pain. J Psychosom Res 1994; 38:523–527 18. Millard RW, Kinsler BL: Evaluation of constricted affect in chronic pain: an attempt using the Toronto Alexithymia Scale. Pain 1992; 50:287–292 19. Gregory RJ, Berry SL: Measuring counterdependency in chronic pain. Psychosom Med 1999; 61:341–345
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20. Derogatis LR, Melisaratos NP: The Brief Symptom Inventory: an introductory report. Psychol Med 1983; 13:595–605 21. Bagby RM, Parker JDA, Taylor GJ: The Twenty-Item Toronto Alexithymia Scale-I. Item selection and cross-validation of the factor structure. J Psychosom Res 1994; 38:23–32 22. Bagby RM, Taylor G, Parker JDA: The Twenty-Item Toronto Alexithymia Scale-II. Convergent, discriminant, and concurrent validity. J Psychosom Res 1994; 38:33–40 23. Barsky AJ, Wyshak G, Klerman GL: The somatosensory amplification scale and its relationship to hypochondriasis. J Psychiatr Res 1990; 24:323–334 24. Zayfert C, McCracken LM, Gross RT: Alexithymia, disability, and emotional distress in chronic nonmalignant pain. Paper presented at the 50th Anniversary Meeting of the American Psychosomatic Society. New York, April 1992
Psychosomatics 41:3, May-June 2000
The authors assessed psychological characteristics of 140 medical outpatients with chronic nonmalignant pain referred for psychiatric consultation. Subjects completed the Toronto Alexithymia Scale, Somatosensory Amplification Scale (SSAS), and Counterdependency Scale (CDS). The only psychological measure able to differentiate the chronic pain group from the control subjects was the CDS. However, SSAS scores were significantly higher in subjects having pain involving the head, chest, abdomen, or pelvis than in subjects having pain only in their backs or extremities. The latter subgroup had significantly higher CDS scores. The findings suggest that there are discrete subgroups within the chronic pain population defined by pain location and specific psychological characteristics. (Psychosomatics 2000; 41:216–220)
D
espite extensive writing and research in this area, there is no consensus regarding the psychological characteristics of patients having chronic benign pain. It was formerly believed that pain fulfilled unconscious needs for guilt or masochism1,2 or served as a release for emotional pain.3 More rigorous studies in the 1970s focused on the application of the Minnesota Multiphasic Personality Inventory (MMPI) and the discovery of the “Conversion V” MMPI profile, [i.e., elevation of the hypochondriasis (Hy) and hysteria (Hs) scales with a lesser elevation of the depression (D) scale]. This pattern differentiated chronic pain patients from patients having acute pain,4 but correlations with treatment outcome have been mixed.5 Evidence that the Conversion V profile represents a nonspecific reaction to illness6 and that the Hy and Hs scales are largely somatic checklists have limited the Conversion V’s application and relevance. More recently, focus has shifted to behavioral and cogReceived June 3, 1999; revised August 24, 1999; accepted September 29, 1999. From the Department of Psychiatry, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210. Address reprint requests to Dr. Gregory. Copyright 䉷 2000 The Academy of Psychosomatic Medicine.
216
nitive aspects of chronic pain, such as helplessness, pessimism, and catastrophic fears.7,8 The concept of somatosensory amplification9 has been applied to the chronic pain population to explain how maladaptive cognitions may lead to heightened pain perception.10 Initial studies indicate that in chronic pain populations, somatosensory amplification may be more determined by levels of anxiety and depression than pain per se.11,12 Another development has been the application of the concept of alexithymia to chronic pain. As first described by Sifneos in 1972,13,14 alexithymic traits include difficulties identifying and describing feelings, impoverishment of fantasy life, and excessive preoccupation with physical symptoms and external events. Alexithymia was initially attributed to patients with psychosomatic illnesses,15 but alexithymia has also been reported in patients having posttraumatic stress disorder, eating disorders, panic disorder, and substance use disorders.16 Attempts to apply the alexithymic construct to chronic pain populations have produced mixed results, perhaps because of the confounding effects of psychiatric comorbidity.11,17,18 A need was identified for a psychological marker more specifically associated with chronic pain.11 Psychosomatics 41:3, May-June 2000
Gregory et al. Gregory and Berry19 recently reviewed clinical vignettes of chronic pain patients in past literature to elaborate the concept of counterdependency. Counterdependent patients are characterized by emotional suppression, idealization of relationships, strong work ethic, caregiving role identity, and self-reliance. As part of their study, Gregory and Berry validated a scale to describe these characteristics (Counterdependency Scale). Counterdependency traits were strongly associated with chronic pain and appeared independent of anxiety, depression, or psychiatric comorbidity. In the present study, the authors employ measures of somatosensory amplification, alexithymia, and counterdependency in a large chronic pain population in order to address two questions. Which psychological marker best characterizes patients with chronic pain? Are there discrete subgroups within the chronic pain population differentiated by specific psychological characteristics? METHODS Subjects The study population included 220 consecutive patients referred in 1998 to the Outpatient Psychiatry Consultation Program within the SUNY Health Science Center. Sources of referral included a general medicine clinic (n⳱107), primary care physicians in the community (n⳱74), and a pain treatment center (n⳱39). Patients suffering from chronic nonmalignant pain (n⳱140), which is defined as daily pain over the previous 6 months, were compared with 80 patients without pain. Patients having a primary psychotic disorder, cognitive impairment, or inability to complete questionnaires were excluded from the study. The chronic pain subjects were largely unmarried (n⳱79), White (n⳱121), and female (n⳱105). The subjects had a meansⳲstandard deviation (SD) age of 44.7Ⳳ11.2 years and an educational attainment of 12.3Ⳳ2.4 years. Fifty-one subjects reported a history of sexual or physical abuse in childhood. The control group did not significantly differ in any of these characteristics. One hundred and fourteen subjects had pain involving the back and/or extremities, of whom 65 subjects had pain exclusively in these regions. Other pain locations included head (n⳱45), abdomen (n⳱25), chest (n⳱22), and pelvis (n⳱14). Fifty-one subjects had pain in more than one of these locations. Mean duration of pain was 7.6Ⳳ6.9 years. The subjects were characterized by multiple pain diagnoses Psychosomatics 41:3, May-June 2000
and attributions, often with poorly defined etiological mechanisms. Measures DSM-IV diagnoses and social, developmental, and occupational histories were obtained in semistructured clinical interviews by board-certified psychiatrists (RG and JM). We devised an interview format to prompt the psychiatrist to obtain important parts of the patient’s history, such as childhood sexual or physical abuse, thereby ensuring that all relevant information was gathered. Because of the inherent ambiguity in differentiating organic from functional pain, patients were assigned a pain disorder diagnosis if they reported a clear exacerbation of their pain with emotional stress. Patients referred to the program were also administered a series of questionnaires before each interview, including anxiety and depression subscales of the Brief Symptom Inventory (BSI), the Twenty-Item Toronto Alexithymia Scale (TAS-20), the Somatosensory Amplification Scale (SSAS), and the Counterdependency Scale (CDS). The BSI is a symptom checklist derived from the Hopkins Symptom Checklist and has been shown to have good validity and reliability.20 The Toronto Alexithymia Scale and its two modified versions, the TAS-R and TAS-20, are currently the most commonly used and best researched measures of alexithymia.21,22 Somatic amplification refers to a tendency in hypochondriacal patients to scrutinize their bodies for somatosensory input and then amplify and misinterpret the sensation as representing a pathological process.9 The SSAS was designed and validated to measure this concept.23 The CDS is a 5-item scale developed by Gregory and Berry19 after clinical observations that a large subgroup of chronic pain patients did not follow patterns frequently cited in the literature of dependency, neediness, and depression.1–3 Indeed, these patients appeared to minimize emotional distress; describe idealized, shallow relationships with stereotyped roles; and lead overly productive lives until the development of their pain syndrome. Data Analysis Upon approval from our Institutional Review Board, data from interviews and questionnaires were entered into a computer software program for analysis (STATISTICA, Tulsa, Oklahoma). Between-group differences were assessed by independent t-tests for parametric variables and 217
Chronic Pain Pearson chi square for nonparametric variables. Logistic and stepwise regression analyses were employed to assess the determinants of pain location in our sample. To correct for bias inherent in multiple statistical comparisons, a probability value of 0.01 or less was chosen as representing statistical significance. RESULTS Table 1 outlines the common psychiatric diagnostic categories seen in both groups. Mood disorders represent the largest diagnostic category with major depressive disorder diagnosed in 70 (50%) of the subjects with chronic pain and 37 (46%) of the control subjects. Pain disorder was diagnosed in 45 (32%) of the subjects with chronic pain and other somatoform disorders were diagnosed in 25 (18%) (i.e., half the chronic pain sample was diagnosed with a somatoform disorder). Table 2 compares the psychological measures of the two groups. Only CDS scores differentiated the chronic pain subjects from the control subjects. This difference remained significant in an analysis of covariance (ANCOVA) after controlling for differences in rates of personality disorders between the two groups (F⳱37.2, P⳱0.000). Employing Pearson product-moment correlations, CDS scores were not significantly associated with the other psychological measures or diagnostic categories. Table 3 employs the same psychological measures to contrast two subgroups within the chronic pain sample. TABLE 1.
DSM-IV diagnostic categories of 140 subjects with chronic pain compared with 80 subjects in a control group N(%)
Mood disorders Yes No Anxiety disorders Yes No Substance use disorders Yes No Personality disorders* Yes No
Pain (nⴔ140)
Control (nⴔ80)
91 (65) 49 (35)
54 (67) 26 (33)
31 (22) 109 (78)
21 (26) 59 (74)
20 (14) 120 (86)
16 (20) 64 (80)
19 (14) 121 (86)
23 (29) 57 (71)
*Significant difference (Pearson chi-square: v2⳱7.59; df⳱1; P⳱0.006)
218
Subjects having chronic pain only in their back and/or extremities had significantly higher CDS scores than subjects having chronic pain that included other locations (i.e., head, chest, abdomen, or pelvis). In contrast, the latter group had significantly higher SSAS scores. BSI anxiety scores were also higher in this group but did not quite reach statistical significance (t⳱2.37, df⳱138, P⳱0.019). The duration of pain and the frequency of pain disorder diagnosis did not significantly differ between the two groups, but the group of subjects having pain involving the head, chest, abdomen, or pelvis was more likely to have other somatoform diagnoses (v2⳱18.1, df⳱1, P⳱0.000). Although not quite reaching a P⳱0.01 level of statistical
TABLE 2.
Psychological measures in 140 subjects with chronic pain compared with 80 subjects in a control group MeansⴣSD
BSI anxiety BSI depression SSAS TAS-20 CDS*
Pain Group (nⴔ140)
Control Group (nⴔ80)
1.76Ⳳ1.17 1.65Ⳳ1.22 1.81Ⳳ0.823 53.5Ⳳ16.4 2.75Ⳳ0.761
1.62Ⳳ0.964 1.53Ⳳ1.09 1.65Ⳳ0.687 52.7Ⳳ14.6 2.07Ⳳ0.703
Note: BSI⳱Brief Symptom Inventory; SSAS⳱Somatosensory Amplification Scale; TAS-20⳱Toronto Alexithymia Scale; CDS⳱Counterdependency Scale. *Significant difference (unpaired t-test: t⳱6.58, df⳱218, P⳱0.000).
TABLE 3.
Psychological measures in 65 subjects with chronic pain exclusively in the back and/or extremities compared with 75 subjects with chronic pain involving the head, abdomen, pelvis, and/or chest MeansⴣSD
BSI anxiety BSI depression SSAS* TAS-20 CDS**
Back Extremities Group (nⴔ65)
Other Pain Location Group (nⴔ75)
1.51Ⳳ1.16 1.46Ⳳ1.17 1.48Ⳳ0.733 51.4Ⳳ15.5 2.93Ⳳ0.692
1.97Ⳳ1.15 1.81Ⳳ1.25 2.09Ⳳ0.795 55.3Ⳳ17.1 2.59Ⳳ0.787
Note: BSI⳱Brief Symptom Inventory; SSAS⳱Somatosensory Amplification Scale; TAS-20⳱Toronto Alexithymia Scale; CDS⳱Counterdependency Scale. *Significant difference (unpaired t test: t⳱-4.70, df⳱138, P⳱0.000). ** Significant difference (unpaired t-test: t⳱2.67, df⳱138, P⳱0.008).
Psychosomatics 41:3, May-June 2000
Gregory et al. significance, subjects in this group were also more likely to have anxiety disorders (v2 ⳱4.84, df⳱1,P⳱0.028) and to be unmarried (v2⳱5.21, df⳱ 1, P⳱0.023). The two groups did not significantly differ on other demographic and diagnostic parameters. Psychological measures including SSAS and CDS accounted for 17% of the variance in pain location employing stepwise regression analyses. When a somatoform diagnosis (excluding pain disorder) was added to the equation, the combined variables predicted 26% of the variance in pain location. The addition of anxiety disorder and marital status to the regression equation did not appreciably contribute to the variance, indicating that these variables are not independent predictors of pain location. DISCUSSION An important finding from this study is that counterdependency is the best psychological characteristic to differentiate psychiatric consult patients who have chronic pain from those without pain. Although previous studies have indicated that alexithymia also characterizes some chronic pain populations,12,17 there is evidence that the alexithymia is more a function of comorbid psychopathology than chronic pain per se.11,18,24 Given that our control group had roughly the same rates of psychiatric disorders as our study group, it is perhaps not surprising that TAS-20 scores did not differ substantially between them. The finding of high CDS scores in a chronic pain population is consistent with a previous study validating the scale.19 CDS scores are independent of scores of other measured psychological variables and independent of comorbid psychiatric diagnoses. There are many possible ex-
planations for the observed association between chronic pain and counterdependency traits. The one that best fits the authors’ clinical observations is that self-reliant and hard-working individuals who minimize distress are less likely to seek rest and medical attention after an acute injury, thereby increasing their chances for developing a chronic condition. A more detailed analysis of the data from our study revealed that counterdependency traits were unevenly distributed among different pain locations. Subjects with pain exclusively in the back and/or extremities were likely to have strong counterdependency traits. Subjects having pain involving the head, chest, abdomen, or pelvis were more likely to have anxiety, somatic amplification, and a somatoform disorder (excluding pain disorder). Psychological measures accounted for a large proportion of the variance in pain location. To our knowledge the present study marks the first time that distinct subgroups within a chronic pain population have been identified on the basis of psychological characteristics. If confirmed, this finding would have important implications for treatment and prevention programs. An important bias in our study is that all subjects were referred for psychiatric consultation, thereby preselecting a population having high rates of psychopathology. It is also possible that the differences in psychological characteristics between subgroups were because of factors that we did not measure, such as pain intensity or functional impairment. Further studies are needed to clarify the relationship between counterdependency and chronic pain (i.e., whether the relationship is causal and in which direction). Studies evaluating treatment interventions in chronic pain populations should take into account pain locations and psychological characteristics of their samples.
References
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