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Importance of a vast but accessible database
Letter to the Editor
Importance of a Vast but Accessible Database To the Editor: In a recent letter to Pain Forum, Dr. David Fishbain [4] remarked on what he thought were some difficulties with the Minnesota Multiphasic Personality Inventory (MMPI). Essentially, Dr. Fishbain noted "Overall, these studies indicate that the MMPI is not stable and, therefore, does not demonstrate test-retest reliability in certain groups of ill patients including those suffering from pain and, possibly, patients under forms of stress. As such, it is not surprising, therefore, that the MMPI would not demonstrate predictive validity in chronic pain patients." Dr. Fishbain's letter contained several points of inaccuracy and did not reflect an awareness of the substantial MMPI research base that has accumulated over several decades-research that bears directly on his argument. We would like to take this opportunity to address some of the criticisms raised in his letter. It should be noted that Fishbain referred to the MMPI in his letter rather than the modern version of the inventory. In 1989, the original MMPI was superseded by a revised version (the MMPI- 2), which should be used at this time because it is based on a more substantial and more contemporary normative population. However, most of our comments apply to both the original and revised instruments. An examination of a basic MMPI [2] or MMPI-2 [5] textbook would indicate that Fishbain was incorrect in his claims that the MMPI scales are unreliable and are therefore not useful in the assessment of chronic pain patients. Scores of studies on the original MMPI and the MMPI-2 address the test-retest reliability of the scales. Space does not allow for a complete description of this research or even a listing of the studies. Therefore, we will provide a sampling of the studies (see Dahlstrom et al. [2] and Graham [5] for a more complete discussion of MMPI and MMPI-2 reliability). Reliability studies usually have been conducted over a t -week test-retest period with correlations ranging from 0.73 to 0.97 reported [3], but there are a number of studies that have evaluated reliability over longer time spans. For example, Mauger [8] found that test-retest correlations over an 8-month time span ranged from 0.44 to 0.79. One long-term study with the original MMPI conducted a test-retest study over
68
a 30-year time frame [7]. This study found MMPI scores to have modest reliability over very long periods (testretest correlations ranged from 0.28 to 0.74) with some scales such as Si having exceptionally high stability. Finally, in a recent MMPI-2 validity study, using a sample of individuals from a normative aging study, over 1,000 subjects were tested on two occasions 5 years apart [9]. The test-retest correlation for this sample over a 5-year span was quite high (0.60 to 0.85). Another important point to keep in mind is that not all MMPI-2 scales are alike with respect to long-term stability. Some scales are more sensitive to situational factors (e.g., scales 0 and Pt in relation to stress), while others, such as the Si scale, are trait measures that tend to have very high stability overtime. In essence, there are two possible explanations for Fishbain's finding that people may alter some of their test responses when retested with the MMPI-2. First, he may have confused test stability with test sensitivity. Measures of stability (or reliability) assume that the individuals being assessed have not changed between test administrations, and that variations in item responses are due to error or instability. Test sensitivity, in part, refers to the degree that the instrument can detect meaningful changes in the dimensions measured. When circumstances change between test administrations, such as involvement in treatment or exposure to stressful life events, an individual's responses to relevant test items also should change. The "overwhelming evidence" of inadequate MMPI-2 test-retest reliability cited by Fishbain consisted of seven studies of treatment interventions with individuals with chronic pain or duodenal ulcers and one study examining the effects of daily stress on endocrine function, personality, and immune system status. It is hardly surprising that scores on MMPI-2 scales declined as a function of successful treatment or increased in response to cumulative stress effects in these studies. This sensitivity to change actually is a strength of the test and does not indicate that test-retest reliability is poor. To suggest otherwise is tantamount to condemning the reliability of medical tests such as an electrocardiogram or hepatic panel when changes in test values are observed following successful treatment. A second possible explanation that Fishbain should consider is that people sometimes alter their responses to personality items in order to present themselves in particular ways (Le., impression management). For
Pain Forum 6(1): 68-69, 1997
Letter to the Editor example, many chronic pain patients may want to influence their personal injury litigation or compensation claims by amplifying pain-related deficits or problems. An illustration of the influence of situations on test results was shown in a recent study that examined the use of altered test instructions to promote more honesty [1]. These investigators showed that the majority of job applicants who initially responded defensively to testing produced valid profiles when given the opportunity to retake the test after they were informed that they were too defensive the first time and that the test could detect it. Moreover, the second test administration resulted in more individuals acknowledging problems. Obviously, when individuals modify their style of test responding over repeated test administrations for the purpose of altering how others perceive them, the testing conditions have changed and test-retest reliability estimates would be inappropriate. Finally, although we agree that a very literal translation of the term personality implies a focus on trait issues, practitioners familiar with the development and use of both the MMPI and MMPI-2 are aware that both state and trait aspects have long been recognized. Indeed, one of the earliest MMPI (then called the Minnesota Multiphasic Personality Schedule) publications concerned the "measurement of symptomatic depression" [6]. Furthermore, we have difficulty recognizing what advantages there would be to using a "pure trait" personality assessment instrument with any patient population. In fact, Fishbain's contention that the mixture of state and trait measures on the MMPI-2 "contaminates" some scales runs counter to the widely held view that, at any point in time, an individual's presentation reflects the interaction between both state and trait factors. That is why even the most rudimentary MMPI-2 training includes an emphasis on both state and trait aspects of test interpretation. We suggest that Dr. Fishbain's conclusions that the "MMPI cannot be trusted to give a reliable personality profile" are inappropriate given the track record of the instrument with chronic pain patients and with other medical populations. In the hands of a well-trained
69
practitioner, appropriate interpretation of MMPI/MMPI-2 results in chronic pain settings can provide a wealth of personality and symptom information that is both reliable and valid. James N. Butcher University of Minnesota
Michael E. Clark Clinical Director, Pain Program, James A. Haley Veterans Affairs Hospital, Tampa, FL
References 1. Butcher IN, Morfitt R, Rouse SV, Holden RR: Reducing MMPI-2 defensiveness: the effect of specialized instructions on retest validity in a job applicant sample. J Personality Assessment (in press) 2. Dahlstrom WG, Welsh GS, Dahlstrom LE: An MMPI hand book. Vol II. University of Minnesota Press, Minneapolis, 1975 3. Faschingbauer T: A short written form of the group MMPI (Doctoral dissertation, University of North Carolina, 1979). Dissertation Abstracts International 34:409B, 1979 4. Fishbain DA: Some difficulties with the predictive validity of Minnesota Multiphasic Personality Inventory. Pain Forum 5:81-82,1996 5. Graham JR: MMPI-2: Assessing personality and psychopathology. 2nd ed. Oxford University Press, New York, 1993 6. Hathaway SR, McKinley JC: The measurement of symptomatic depression with the Minnesota Multiphasic Personality Schedule. Psychological Bulletin 37:425, 1940 7. Leon G, Gillum B, Gillum R, Gouze M: Personality stability and change over a 30 year period: middle age to old age. J Consult Clin PsychoI47:517-524, 1973 8. Mauger P: The test-retest reliability of personas: an empirical investigation utilizing the MMPI and Personality Research Form (PRF) (Doctoral dissertation, University of Minnesota, 1972). Dissertation Abstracts International 33:2816B,1972 9. Spiro A, Butcher IN, Levenson M. Aldwin C, Bosse: Personality change and. stability of five years: the MMPI-2 in older men. Presented at the Annual Meeting of the American Psychological Association, 1992
Importance of a Vast but Accessible Database To the Editor: In a recent letter to Pain Forum, Dr. David Fishbain [4] remarked on what he thought were some difficulties with the Minnesota Multiphasic Personality Inventory (MMPI). Essentially, Dr. Fishbain noted "Overall, these studies indicate that the MMPI is not stable and, therefore, does not demonstrate test-retest reliability in certain groups of ill patients including those suffering from pain and, possibly, patients under forms of stress. As such, it is not surprising, therefore, that the MMPI would not demonstrate predictive validity in chronic pain patients." Dr. Fishbain's letter contained several points of inaccuracy and did not reflect an awareness of the substantial MMPI research base that has accumulated over several decades-research that bears directly on his argument. We would like to take this opportunity to address some of the criticisms raised in his letter. It should be noted that Fishbain referred to the MMPI in his letter rather than the modern version of the inventory. In 1989, the original MMPI was superseded by a revised version (the MMPI- 2), which should be used at this time because it is based on a more substantial and more contemporary normative population. However, most of our comments apply to both the original and revised instruments. An examination of a basic MMPI [2] or MMPI-2 [5] textbook would indicate that Fishbain was incorrect in his claims that the MMPI scales are unreliable and are therefore not useful in the assessment of chronic pain patients. Scores of studies on the original MMPI and the MMPI-2 address the test-retest reliability of the scales. Space does not allow for a complete description of this research or even a listing of the studies. Therefore, we will provide a sampling of the studies (see Dahlstrom et al. [2] and Graham [5] for a more complete discussion of MMPI and MMPI-2 reliability). Reliability studies usually have been conducted over a t -week test-retest period with correlations ranging from 0.73 to 0.97 reported [3], but there are a number of studies that have evaluated reliability over longer time spans. For example, Mauger [8] found that test-retest correlations over an 8-month time span ranged from 0.44 to 0.79. One long-term study with the original MMPI conducted a test-retest study over
68
a 30-year time frame [7]. This study found MMPI scores to have modest reliability over very long periods (testretest correlations ranged from 0.28 to 0.74) with some scales such as Si having exceptionally high stability. Finally, in a recent MMPI-2 validity study, using a sample of individuals from a normative aging study, over 1,000 subjects were tested on two occasions 5 years apart [9]. The test-retest correlation for this sample over a 5-year span was quite high (0.60 to 0.85). Another important point to keep in mind is that not all MMPI-2 scales are alike with respect to long-term stability. Some scales are more sensitive to situational factors (e.g., scales 0 and Pt in relation to stress), while others, such as the Si scale, are trait measures that tend to have very high stability overtime. In essence, there are two possible explanations for Fishbain's finding that people may alter some of their test responses when retested with the MMPI-2. First, he may have confused test stability with test sensitivity. Measures of stability (or reliability) assume that the individuals being assessed have not changed between test administrations, and that variations in item responses are due to error or instability. Test sensitivity, in part, refers to the degree that the instrument can detect meaningful changes in the dimensions measured. When circumstances change between test administrations, such as involvement in treatment or exposure to stressful life events, an individual's responses to relevant test items also should change. The "overwhelming evidence" of inadequate MMPI-2 test-retest reliability cited by Fishbain consisted of seven studies of treatment interventions with individuals with chronic pain or duodenal ulcers and one study examining the effects of daily stress on endocrine function, personality, and immune system status. It is hardly surprising that scores on MMPI-2 scales declined as a function of successful treatment or increased in response to cumulative stress effects in these studies. This sensitivity to change actually is a strength of the test and does not indicate that test-retest reliability is poor. To suggest otherwise is tantamount to condemning the reliability of medical tests such as an electrocardiogram or hepatic panel when changes in test values are observed following successful treatment. A second possible explanation that Fishbain should consider is that people sometimes alter their responses to personality items in order to present themselves in particular ways (Le., impression management). For
Pain Forum 6(1): 68-69, 1997
Letter to the Editor example, many chronic pain patients may want to influence their personal injury litigation or compensation claims by amplifying pain-related deficits or problems. An illustration of the influence of situations on test results was shown in a recent study that examined the use of altered test instructions to promote more honesty [1]. These investigators showed that the majority of job applicants who initially responded defensively to testing produced valid profiles when given the opportunity to retake the test after they were informed that they were too defensive the first time and that the test could detect it. Moreover, the second test administration resulted in more individuals acknowledging problems. Obviously, when individuals modify their style of test responding over repeated test administrations for the purpose of altering how others perceive them, the testing conditions have changed and test-retest reliability estimates would be inappropriate. Finally, although we agree that a very literal translation of the term personality implies a focus on trait issues, practitioners familiar with the development and use of both the MMPI and MMPI-2 are aware that both state and trait aspects have long been recognized. Indeed, one of the earliest MMPI (then called the Minnesota Multiphasic Personality Schedule) publications concerned the "measurement of symptomatic depression" [6]. Furthermore, we have difficulty recognizing what advantages there would be to using a "pure trait" personality assessment instrument with any patient population. In fact, Fishbain's contention that the mixture of state and trait measures on the MMPI-2 "contaminates" some scales runs counter to the widely held view that, at any point in time, an individual's presentation reflects the interaction between both state and trait factors. That is why even the most rudimentary MMPI-2 training includes an emphasis on both state and trait aspects of test interpretation. We suggest that Dr. Fishbain's conclusions that the "MMPI cannot be trusted to give a reliable personality profile" are inappropriate given the track record of the instrument with chronic pain patients and with other medical populations. In the hands of a well-trained
69
practitioner, appropriate interpretation of MMPI/MMPI-2 results in chronic pain settings can provide a wealth of personality and symptom information that is both reliable and valid. James N. Butcher University of Minnesota
Michael E. Clark Clinical Director, Pain Program, James A. Haley Veterans Affairs Hospital, Tampa, FL
References 1. Butcher IN, Morfitt R, Rouse SV, Holden RR: Reducing MMPI-2 defensiveness: the effect of specialized instructions on retest validity in a job applicant sample. J Personality Assessment (in press) 2. Dahlstrom WG, Welsh GS, Dahlstrom LE: An MMPI hand book. Vol II. University of Minnesota Press, Minneapolis, 1975 3. Faschingbauer T: A short written form of the group MMPI (Doctoral dissertation, University of North Carolina, 1979). Dissertation Abstracts International 34:409B, 1979 4. Fishbain DA: Some difficulties with the predictive validity of Minnesota Multiphasic Personality Inventory. Pain Forum 5:81-82,1996 5. Graham JR: MMPI-2: Assessing personality and psychopathology. 2nd ed. Oxford University Press, New York, 1993 6. Hathaway SR, McKinley JC: The measurement of symptomatic depression with the Minnesota Multiphasic Personality Schedule. Psychological Bulletin 37:425, 1940 7. Leon G, Gillum B, Gillum R, Gouze M: Personality stability and change over a 30 year period: middle age to old age. J Consult Clin PsychoI47:517-524, 1973 8. Mauger P: The test-retest reliability of personas: an empirical investigation utilizing the MMPI and Personality Research Form (PRF) (Doctoral dissertation, University of Minnesota, 1972). Dissertation Abstracts International 33:2816B,1972 9. Spiro A, Butcher IN, Levenson M. Aldwin C, Bosse: Personality change and. stability of five years: the MMPI-2 in older men. Presented at the Annual Meeting of the American Psychological Association, 1992