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The minnesota multiphasic personality inventory in chronic pain
Commentary
The Minnesota Multiphasic Personality Inventory in Chronic Pain Security Blanket or Sound Investment? Francis J. Keefe, "t John C. Lefebvre, t and Pat M. Beaupre*
he Focus article by Main and Spanswick raises some important issues about personality testing in general, and the Minnesota Multiphasic Personality Inventory (MMPI) in particular, in the assessment of patients with chronic pain. The article touches on aspects of the history of the MMPI that may be unfamiliar to many pain specialists and provides a good summary of prior critiques of this instrument. Although we agree with many of the points raised by Main and Spanswick, we disagree with other points and feel that certain critical areas have been ignored. This commentary is divided into two sections. In the first section, a number of points raised by Main and Spanswick are identified and elaborated on. The second section highlights a number of issues that were not addressed in the Focus article, but have important implications for clinical and research applications of personality assessment for this field.
T
PERSONALITY ASSESSMENT AND THE MMPI: A CRITICAL APPRAISAL One of the most important points raised by Main and Spanswick is that early theories of chronic pain were overly simplified. One problem with simplistic theories is that they are very likely to entice individuals to apply available assessment tools in an overly simplistic fashion. The MMPI 5 was one of the few personality assessment instruments available to psychologists working with patients with chronic pain in the early days of clinical pain research. Although this instrument enables one to assess personality in a multidimensional fashion, it was often used by clinicians trying to make simple
From 'Duke Universrty Medical Center and the tDepartment of Psychology: Social and Health Sciences, Duke University, NC. Reprint requests: Dr. F. Keefe, Pain Management Program, Box 3159, Duke Medical Center, Durham, NC 27710.
Pain Forum 4(2): 101-103, 1995
dichotomous discriminations between functional and organic pain. The low back pain subscale is an excellent example of this tendency.' The fault with the MMPI may lie, not so much in the instrument, but in the way that it came be used in clinical practice. This problem is not only evident with respect to psychological testing, but also with physical assessments such as the graduated spinal anesthesia assessment." The development of new theories that view pain as a complex, multidimensional experience has challenged such simplistic thinking. These theories have not only led to new pain treatments, they have also heightened recognition that the information obtained from pain assessment instruments needs to be interpreted in a much broader context. Numerous studies have shown that patients with chronic pain have elevations on scales 1 and 3 of the MMPI. A naive interpretation of this type of profile is that these patients are overly preoccupied with their physical symptoms. As pointed out by Main and Spanswick, although patients with chronic pain will tend to endorse items on these scales frequently, this pattern is not necessarily indicative of psychopathology. Items on these scales measure such things as problems with fatigue, weakness secondary to deconditioning, appetite, and headaches, all of which are common in individuals having chronic pain.' We agree with Main and Spanswick that the inordinate amount of research effort devoted to understanding the personality of patients with chronic pain has meant that much less attention has been given to understanding the role that environmental factors can play in chronic pain. Social system factors (e.g., workers' compensation, overly solicitous family), the legal system (e.g., pain-related litigation), and problems in the medical system (e.g., delays in treating pain and overtreatment of benign pain conditions) can serve to elicit and maintain high levels of emotional distress and pain behavior. With the help of data from recent longitudinal 101
102
COMMENTARY/Keefe et al,
studies researchers are beginning to understand how these and other factors influence pain and pain behavior over time.'?" The fact that pain specialists have only recently become involved in such research is due in large measure to the fact that they have historically focused on the individual with pain, rather than on the social context in which that individual lives. Main and Spanswick believe that pain research needs to move away from an analysis of personality to focus on other predictors of treatment outcome. This is a very pragmatic position that may have implications for prevention. The track record of psychological research on predictors of outcome of treatments for chronic pain, however, is inconsistent at best." Can we expect significant findings to emerge from new behavioral treatment outcome research? Main and Spanswick identify a number of new methodologies that might provide a more sophisticated analysis of psychological variables. These methodologies include the use of structural equation modeling and classification and regression tree analysis. These sophisticated techniques promise to more meaningfully link a number of psychological phenomena (e.g., self-efficacy, pain beliefs, and depression) to treatment outcome. However, if these methods are to be useful in studying other potentially important phenomena identified by Main and Spanswick (e.g., central nervous system learning, perhaps as indexed by magnetic resonance imaging) and social/environmental factors (e.g., solicitious spousal responding, perhaps indexed by behavioral observation), researchers will need to develop more practical ways to measure these variables.
IMPORTANT ISSUES FOR CLINICAL PRACTICE AND FUTURE RESEARCH Clinicians who have a familiarity with personality testing may be concerned that Main and Spanswick highlight the limitations of the personality instruments such as MMPI, but fail to underscore many of their strengths. First, scores on these instruments are standardized. This enables one to compare an individual patient with relevant reference groups. The MMPI-2, for example, has recently adopted standards that are age determined. Second, the MMPI was designed for use in populations of patients having psychopathology. It does a good job of identifying severe psychopathology, such as thought disorders or psychotic depression. Patients who have failed to respond to multiple treatment trials may do so because they suffer from undetected psychopathology. The MMPI is particularly useful with this population. A patient may appear depressed, masking other significant psychopathology. Additionally, interpretation of the results of the MMPI can suggest new treatment directions other than conventional pain manage-
ment approaches, for example, intensive psychotherapy or psychotropic medications. When the MMPI is used clinically, interpretation is typically based, not on a single scale, but on a pattern of scores on multiple scales (a profile). Research by Bradley and colleaquss-" has identified homogeneous MMPI profile subgroups based on a cluster analysis of the entire 10 clinical scales of the MMPI. The fact that these empirically derived profiles have been replicated across several studies is impressive. MMPI profile subgroups are the subject of much current research and may prove to be useful in understanding and predicting the course of chronic pain. The profile subgroups, although identified empirically, share some similarities with the clinical use of this instrument. They are based on a pattern of scores and recognition that pain populations are heterogeneous and that within these populations homogeneous groups can be identified based on a broad assessment of personality features. One topic that was ignored by Main and Spanswick but that may be important in interpreting the MMPI in chronic pain patients is the use of the Harris-Lingoes subscales of the MMPI. These subscales were developed in order to systematically analyze subgroups of related items on particular clinical scales.' For example, for MMPI scale 3Hysteria, there are five Harris-Lingoes subscales: denial of social anxiety, need for affection, lassitude and malaise, somatic complaints, and inhibition of aggression. In interpreting the MMPI profiles of patients with chronic pain it can be helpful to identify what subgroupings of items have caused the elevation on a particular scale. If the patient's score on scale 3 was high because of endorsing many somatic complaint items, the interpretation would be different than if the elevation was due to endorsements of items related to inhibition of aggression. Examination of these subscales might be particularly useful in prospective studies. For example, in a study performed at Boeing Aircraft Company, Bigos et at.' found that scale 3 of the MMPI was a significant predictor of the development of low back injuries. In a subsequent study these investigators used the Harris-Lingoes subscales to identify which item subgroups on scale 3 were most strongly associated with the development of low back injuries: Their findings showed that three of the subscales were strongly related to outcome (lassitude and malaise, denial of social anxiety, and need for affection), whereas the other two subscales (somatic complaints and inhibition of aggression) were not. Additional research is needed to examine the utility of the Harris-Lingoes subscales in explaining the onset and maintenance of pain complaints. Researchers interested in this area, however, should be aware that some of the scales are made up of a very small number of items (e.g., as few as six) and that reliabilitymay be a concern. Graham' reports that the Kuder-Richardson value (a measure of intemal consistency) for the Harris-Lingoes
COMMENTARY/Keefe et al.
scale measuring inhibition of aggression is .31, which is quite low.
CONCLUSIONS Main and Spanswick focus on the weaknesses of the MMPI. This instrument clearly has both strengths and weaknesses. The MMPI is currently the most widely used psychological test instrument and is likely to retain that status. Training is required to interpret MMPI profiles obtained from patients with chronic pain. Clinicians need to keep in mind that information from the MMPI should be combined with information from other sources, including interviews with the patient and family, pain diaries, behavioral observation, and other standardized self-report instruments (e.g., the McGill Pain Questionnaire, the Multidimensional Pain inventory, the Coping Strategy Questionnaire). The MMPI, like many other pain assessment tools, is only as good as the clinician who interprets it.
References 1. Bigos SJ, Battie MC, Spengler OM et al: A longitudinal, prospective study of industrial back injury reporting. Clin Orthop 279:21-34, 1992 2. Bradley LA, Prokop CK, Margolis R, Gentry WD: Multivariate analyses of the MMPI profiles of low back pain patients. J Behav Med 1:253-272, 1978
103
3. Bradley LA, Van der Heide LH: Pain related correlates of MMPI profile subgroups among back pain patients. Health PsychoI3:157-174, 1984 4. Fordyce WE, Bigos SJ, Battie MC, Fisher LD: MMPI scale 3 as a predictor of back injury report: what does it tell us? Clin J Pain 8:222-226, 1992 5. Graham JR: The MMPI: a practical guide. 2nd ed. Oxford University Press, New York, 1987 6. Keefe FJ, Brown C, Scott 0, Ziesat H: Behavioral assessment of chronic pain. pp. 321-350. In Keefe FJ, Blumenthal JA (eds): Assessment strategies in behavioral medicine. Grune & Stratton, New York, 1982 7. Pincus T, Callahan LF, Bradley LA, Vaughn WK, Wolfe F: Elevated MMPI scores on hypochondriasis, depression, and hysteria in patients with rheumatoid arthritis reflect disease rather than psychological status. Arthritis Rheum 29:1456-1466, 1986 8. Prokop CK, Bradley LA, Margolis R, Gentry WD: Multivariate analysis of the MMPI profiles of patients with multiple pain complaints. J Pers Assess 44:246-252, 1980 9. Urban BJ, McKain CW: Local anesthetic effect of intrathecal normal saline. Pain 5:43-52, 1978 10. Von Korff M, Deyo RA, Cherkin 0, Barlow W: Back injury in primary care: outcomes at 1 year. Spine 18:855-862, 1993 11. Von Korff M, Le Resche L, Dworkin SF: First onset of common pain symptoms: a prospective study of depression as a risk factor. Pain 55:251-258, 1993
The Minnesota Multiphasic Personality Inventory in Chronic Pain Security Blanket or Sound Investment? Francis J. Keefe, "t John C. Lefebvre, t and Pat M. Beaupre*
he Focus article by Main and Spanswick raises some important issues about personality testing in general, and the Minnesota Multiphasic Personality Inventory (MMPI) in particular, in the assessment of patients with chronic pain. The article touches on aspects of the history of the MMPI that may be unfamiliar to many pain specialists and provides a good summary of prior critiques of this instrument. Although we agree with many of the points raised by Main and Spanswick, we disagree with other points and feel that certain critical areas have been ignored. This commentary is divided into two sections. In the first section, a number of points raised by Main and Spanswick are identified and elaborated on. The second section highlights a number of issues that were not addressed in the Focus article, but have important implications for clinical and research applications of personality assessment for this field.
T
PERSONALITY ASSESSMENT AND THE MMPI: A CRITICAL APPRAISAL One of the most important points raised by Main and Spanswick is that early theories of chronic pain were overly simplified. One problem with simplistic theories is that they are very likely to entice individuals to apply available assessment tools in an overly simplistic fashion. The MMPI 5 was one of the few personality assessment instruments available to psychologists working with patients with chronic pain in the early days of clinical pain research. Although this instrument enables one to assess personality in a multidimensional fashion, it was often used by clinicians trying to make simple
From 'Duke Universrty Medical Center and the tDepartment of Psychology: Social and Health Sciences, Duke University, NC. Reprint requests: Dr. F. Keefe, Pain Management Program, Box 3159, Duke Medical Center, Durham, NC 27710.
Pain Forum 4(2): 101-103, 1995
dichotomous discriminations between functional and organic pain. The low back pain subscale is an excellent example of this tendency.' The fault with the MMPI may lie, not so much in the instrument, but in the way that it came be used in clinical practice. This problem is not only evident with respect to psychological testing, but also with physical assessments such as the graduated spinal anesthesia assessment." The development of new theories that view pain as a complex, multidimensional experience has challenged such simplistic thinking. These theories have not only led to new pain treatments, they have also heightened recognition that the information obtained from pain assessment instruments needs to be interpreted in a much broader context. Numerous studies have shown that patients with chronic pain have elevations on scales 1 and 3 of the MMPI. A naive interpretation of this type of profile is that these patients are overly preoccupied with their physical symptoms. As pointed out by Main and Spanswick, although patients with chronic pain will tend to endorse items on these scales frequently, this pattern is not necessarily indicative of psychopathology. Items on these scales measure such things as problems with fatigue, weakness secondary to deconditioning, appetite, and headaches, all of which are common in individuals having chronic pain.' We agree with Main and Spanswick that the inordinate amount of research effort devoted to understanding the personality of patients with chronic pain has meant that much less attention has been given to understanding the role that environmental factors can play in chronic pain. Social system factors (e.g., workers' compensation, overly solicitous family), the legal system (e.g., pain-related litigation), and problems in the medical system (e.g., delays in treating pain and overtreatment of benign pain conditions) can serve to elicit and maintain high levels of emotional distress and pain behavior. With the help of data from recent longitudinal 101
102
COMMENTARY/Keefe et al,
studies researchers are beginning to understand how these and other factors influence pain and pain behavior over time.'?" The fact that pain specialists have only recently become involved in such research is due in large measure to the fact that they have historically focused on the individual with pain, rather than on the social context in which that individual lives. Main and Spanswick believe that pain research needs to move away from an analysis of personality to focus on other predictors of treatment outcome. This is a very pragmatic position that may have implications for prevention. The track record of psychological research on predictors of outcome of treatments for chronic pain, however, is inconsistent at best." Can we expect significant findings to emerge from new behavioral treatment outcome research? Main and Spanswick identify a number of new methodologies that might provide a more sophisticated analysis of psychological variables. These methodologies include the use of structural equation modeling and classification and regression tree analysis. These sophisticated techniques promise to more meaningfully link a number of psychological phenomena (e.g., self-efficacy, pain beliefs, and depression) to treatment outcome. However, if these methods are to be useful in studying other potentially important phenomena identified by Main and Spanswick (e.g., central nervous system learning, perhaps as indexed by magnetic resonance imaging) and social/environmental factors (e.g., solicitious spousal responding, perhaps indexed by behavioral observation), researchers will need to develop more practical ways to measure these variables.
IMPORTANT ISSUES FOR CLINICAL PRACTICE AND FUTURE RESEARCH Clinicians who have a familiarity with personality testing may be concerned that Main and Spanswick highlight the limitations of the personality instruments such as MMPI, but fail to underscore many of their strengths. First, scores on these instruments are standardized. This enables one to compare an individual patient with relevant reference groups. The MMPI-2, for example, has recently adopted standards that are age determined. Second, the MMPI was designed for use in populations of patients having psychopathology. It does a good job of identifying severe psychopathology, such as thought disorders or psychotic depression. Patients who have failed to respond to multiple treatment trials may do so because they suffer from undetected psychopathology. The MMPI is particularly useful with this population. A patient may appear depressed, masking other significant psychopathology. Additionally, interpretation of the results of the MMPI can suggest new treatment directions other than conventional pain manage-
ment approaches, for example, intensive psychotherapy or psychotropic medications. When the MMPI is used clinically, interpretation is typically based, not on a single scale, but on a pattern of scores on multiple scales (a profile). Research by Bradley and colleaquss-" has identified homogeneous MMPI profile subgroups based on a cluster analysis of the entire 10 clinical scales of the MMPI. The fact that these empirically derived profiles have been replicated across several studies is impressive. MMPI profile subgroups are the subject of much current research and may prove to be useful in understanding and predicting the course of chronic pain. The profile subgroups, although identified empirically, share some similarities with the clinical use of this instrument. They are based on a pattern of scores and recognition that pain populations are heterogeneous and that within these populations homogeneous groups can be identified based on a broad assessment of personality features. One topic that was ignored by Main and Spanswick but that may be important in interpreting the MMPI in chronic pain patients is the use of the Harris-Lingoes subscales of the MMPI. These subscales were developed in order to systematically analyze subgroups of related items on particular clinical scales.' For example, for MMPI scale 3Hysteria, there are five Harris-Lingoes subscales: denial of social anxiety, need for affection, lassitude and malaise, somatic complaints, and inhibition of aggression. In interpreting the MMPI profiles of patients with chronic pain it can be helpful to identify what subgroupings of items have caused the elevation on a particular scale. If the patient's score on scale 3 was high because of endorsing many somatic complaint items, the interpretation would be different than if the elevation was due to endorsements of items related to inhibition of aggression. Examination of these subscales might be particularly useful in prospective studies. For example, in a study performed at Boeing Aircraft Company, Bigos et at.' found that scale 3 of the MMPI was a significant predictor of the development of low back injuries. In a subsequent study these investigators used the Harris-Lingoes subscales to identify which item subgroups on scale 3 were most strongly associated with the development of low back injuries: Their findings showed that three of the subscales were strongly related to outcome (lassitude and malaise, denial of social anxiety, and need for affection), whereas the other two subscales (somatic complaints and inhibition of aggression) were not. Additional research is needed to examine the utility of the Harris-Lingoes subscales in explaining the onset and maintenance of pain complaints. Researchers interested in this area, however, should be aware that some of the scales are made up of a very small number of items (e.g., as few as six) and that reliabilitymay be a concern. Graham' reports that the Kuder-Richardson value (a measure of intemal consistency) for the Harris-Lingoes
COMMENTARY/Keefe et al.
scale measuring inhibition of aggression is .31, which is quite low.
CONCLUSIONS Main and Spanswick focus on the weaknesses of the MMPI. This instrument clearly has both strengths and weaknesses. The MMPI is currently the most widely used psychological test instrument and is likely to retain that status. Training is required to interpret MMPI profiles obtained from patients with chronic pain. Clinicians need to keep in mind that information from the MMPI should be combined with information from other sources, including interviews with the patient and family, pain diaries, behavioral observation, and other standardized self-report instruments (e.g., the McGill Pain Questionnaire, the Multidimensional Pain inventory, the Coping Strategy Questionnaire). The MMPI, like many other pain assessment tools, is only as good as the clinician who interprets it.
References 1. Bigos SJ, Battie MC, Spengler OM et al: A longitudinal, prospective study of industrial back injury reporting. Clin Orthop 279:21-34, 1992 2. Bradley LA, Prokop CK, Margolis R, Gentry WD: Multivariate analyses of the MMPI profiles of low back pain patients. J Behav Med 1:253-272, 1978
103
3. Bradley LA, Van der Heide LH: Pain related correlates of MMPI profile subgroups among back pain patients. Health PsychoI3:157-174, 1984 4. Fordyce WE, Bigos SJ, Battie MC, Fisher LD: MMPI scale 3 as a predictor of back injury report: what does it tell us? Clin J Pain 8:222-226, 1992 5. Graham JR: The MMPI: a practical guide. 2nd ed. Oxford University Press, New York, 1987 6. Keefe FJ, Brown C, Scott 0, Ziesat H: Behavioral assessment of chronic pain. pp. 321-350. In Keefe FJ, Blumenthal JA (eds): Assessment strategies in behavioral medicine. Grune & Stratton, New York, 1982 7. Pincus T, Callahan LF, Bradley LA, Vaughn WK, Wolfe F: Elevated MMPI scores on hypochondriasis, depression, and hysteria in patients with rheumatoid arthritis reflect disease rather than psychological status. Arthritis Rheum 29:1456-1466, 1986 8. Prokop CK, Bradley LA, Margolis R, Gentry WD: Multivariate analysis of the MMPI profiles of patients with multiple pain complaints. J Pers Assess 44:246-252, 1980 9. Urban BJ, McKain CW: Local anesthetic effect of intrathecal normal saline. Pain 5:43-52, 1978 10. Von Korff M, Deyo RA, Cherkin 0, Barlow W: Back injury in primary care: outcomes at 1 year. Spine 18:855-862, 1993 11. Von Korff M, Le Resche L, Dworkin SF: First onset of common pain symptoms: a prospective study of depression as a risk factor. Pain 55:251-258, 1993