The evolution of the definition of pain and the influence of the importance of various biopsychosocial factors can be observed through various theories, all of which attempt to provide a better understanding of the process of pain. One universal assumption held by each of these theories is of pain as a subjective experience, meaning that each individual may subjectively feel, experience, and interpret the meaning of their pain uniquely.
Models of Pain
Gate-Control Theory of Pain
The first major modernized medical model theory of pain, the gate-control theory, emphasized the close interaction between psychosocial and physiologic processes. The gate-control theory of pain describes how thoughts, feelings, and behavior affect pain. The hypothesis is that a “gate,” located within the human brain, determines the individual’s impression of pain. The gate may be opened or closed—this determines the amount of pain the individual experiences. The underlying assumption is that the pain message originates at the site of aggravation, the signal is transmitted to the brain, and the pain is then brought into the individual’s awareness.
There are many ways in which an individual may “open” or “close” the gate. Using coping strategies may close the gate (meaning that the brain will either not recognize or give credence to the pain signal), while allowing oneself to focus on thoughts of pain may open the gate (bringing the pain signal into the brain’s awareness). Negative thinking, nonconstructive, pessimistic thinking may also open the gate, as will stress, anxiety, tension, helplessness, anger, hopelessness, and despair.
The ultimate conclusion from this theory is that the process of pain can therefore be mediated by changing the way an individual cognitively processes the pain experience. This theory is often useful in clinical practice as a means of explaining pain to patients, and aids the clinician in treating pain via cognitive therapy; however, the scientific community has demanded a more comprehensive theory that accounts for the neurophysiology, neurotransmission, and opioid receptors that may all be involved in understanding and defining pain. This demand was the precursor to the neuromatrix model of pain.
Neuromatrix Model of Pain
The term neuromatrix refers to the neural network involved in the perception of pain. The neuromatrix theory integrates physiologic and psychological evidences, and assumes pain to be a multifaceted experience, with pain sensations produced by specific patterns of nerve impulses generated by a widely distributed neural network.
The neuromatrix model may be viewed as a diathesis-stress approach, meaning that predispositional factors interact with acute stressors to result in a pathologic state. The experience of pain might be thought of as such a stressor. Further explained, the theory proposes that when an organism is injured, there is an interruption of homeostatic regulation. This disruption is not only physically stressful, but it also creates psychological stress. This in turn initiates a complex response aimed at restoring homeostasis (homeostasis being the previously nonpainful state of the body). This process of homeostatic restoration can add further physical and psychological stress.
Physiologically, the body may experience deleterious effects, such as immune system suppression, hypertension, and physical discomfort such as stomach pains or heart burn. The psychological aspects of pain result in the body activating the limbic system. The limbic system plays an important role in experiencing and regulating emotions, motivation of actions, and contributes to thought patterns. In the case of pain, one’s subjective interpretation of the pain experience, fear, and anxiety all further remove the body from homeostasis. Thus, once pain is established and the body activates the necessary mechanisms to return to homeostasis, any future or additional experience of pain will be physiologically and psychologically viewed as a continual threat that creates harmful demands on the body. Thus, a cycle develops that contributes to and maintains the pain-stress process. The neuromatrix hypothesis suggests that an individual’s unique genetic makeup and his or her own subjective experience of pain are the chief components that determine the nature of the pain the organism will experience and is the basis for individual differences in the pain experience.
Both the gate-control theory and the neuromatrix model have attempted to integrate and define a great deal of psychological and physiologic scientific data, although it is thought neither of them provides a fully adequate theory to define the pain experience. They do, however, point to what is currently the most promising approach to understanding pain: the biopsychosocial approach. This approach views physical disorders, including pain, as the result of a dynamic interaction between physiologic, psychologic, and social factors that can heavily influence a subject’s clinical presentation.
Biopsychosocial Model of Pain
In an effort to explain why individual experiences of pain are unique, the biopsychosocial model examines how psychological, social, and economic factors can interact with physical pathology to modulate a patient’s report of symptoms and subsequent disability. This understanding has been the foundation for a major paradigm shift in the assessment and management of pain, moving away from a traditional biomedical reductionist approach to this more comprehensive biopsychosocial approach. In fact, this paradigm shift is so dramatic that it has resulted is a mandate from the Joint Commission on the Accreditation of Healthcare Organizations requiring physicians to consider pain as a fifth vital sign. The Pain Care Bill of Rights of the nonprofit American Pain Foundation calls for management of all types of pain, both malignant and nonmalignant.
In order to understand pain in view of the biopsychosocial model, it seems helpful to examine the distinction between disease and illness. The term disease is generally used to define “an objective biological event” that involves the disruption of specific body structures or organ systems, caused by anatomic, pathologic, or physiologic changes. Illness, in contrast, is generally defined as a subjective experience or self-attribution of disease being present. An illness will yield physical discomfort, behavioral limitations, and psychosocial distress. Therefore, illness references how a sick individual and members of his or her family live with and respond to symptoms and their resulting disabilities.
To illustrate this distinction between disease and illness is analogous to the distinction made between nociception and pain. Nociception involves the stimulation of nerves that convey information about tissue damage to the brain. Pain, however, is a more subjective perception that is the result of the transduction, transmission, and modulation of sensory input, and may be filtered through an individual’s genetic composition, prior learning history, current physiologic status, and sociocultural influences. The combination of the physiologic experience of pain and the debilitating behavior that can accompany it are the expressions of suffering and pain behavior.
Based on this notion, it is thought that pain cannot be comprehensively assessed without a full understanding of the person who is exposed to the nociception. The biopsychosocial model focuses on illness. With this perspective, diversity in pain behavior can be expected as illness experience varies from person to person. This may include severity, duration, and psychological consequences. The interrelationships among biologic changes, psychological status, and the social and cultural context all need to be taken into account in fully understanding the pain patient’s perception of and response to illness. A model or treatment approach that focuses on only one of these core set of factors will be insufficient to effectively assess and treat the patient. The biopsychosocial model has consistently demonstrated the heuristic technique in treatment.
When interpreting pain using the biopsychosocial model, clinicians should be aware that each of the three constructs in the model are different in their composition. Therefore, their assessment will be accomplished through different means and processes. Pain likely should be viewed longitudinally as an ongoing, multifactorial process in which there is dynamic interplay between the biologic, psychological, and social cultural factors that shape the experience and responses of patients.
To comprehensively assess pain, it is important to account for potential interactions in the process of prescribing the best treatment regimen, individualized for a particular patient with pain. For example, a patient may present with pain resulting from an earlier accident that produced severe musculoskeletal injuries, such as bone fractures and ligament tears, that have not completely healed. In addition to these physical injuries and resultant pain, the accident may have led to the inability to return to work. The patient might also have self-esteem problems because he or she is viewed as being disabled and is stigmatized by this situation. This may have resulted in economic problems and stressors because of the sudden decrease in income. There are debts to be paid, causing family stress, turmoil, and guilt. If this patient comes from a culture in which work and activity are highly valued there may be even more psychosocial distress. Thus, there are potentially multiple levels of psychosocial stressors that all need to be assessed and considered before one can develop a comprehensive pain management program for a patient who may not be responding to conventional or conservative care as might be expected.
Another model outlined four dimensions associated with the concept of pain: (1) nociception (2) pain (3) suffering and (4) pain behavior. Nociception refers to the actual physical units that might affect specialized nerve fibers and signal the central nervous system that an aversive event has occurred. This may include chemical irritant, physical/mechanical, or thermal pain. Pain is the sensation arising as the result of perceived nociception. However, this definition is overly simplistic because sometimes pain is perceived in the absence of nociception. An example of this would be phantom limb pain. On the contrary nociception has been recorded to occur without being perceived, such as an individual who is in shock after experiencing a very severe injury. Nociception and pain act as signals to the central nervous system. Suffering is a reaction to these signals that can be affected by past experiences as well as anticipation of future events, and refers to the emotional association with it, such as fear, threat, or loss. Because of a specific painful episode, anxiety and depression may develop as a consequence to the pain behavior. Pain behavior refers to things that individuals do when they are suffering or currently experiencing pain. For example, a person may avoid driving after experiencing an injury due to an accident. The implications for pain behavior can range from avoiding certain activities to more debilitating problems such as developing generalized anxiety surrounding any activity the person must participate in to have a functional life. As such, the interaction in the range of biopsychosocial factors can be quite broad. There are times when the nature of the patient’s response to treatment may have less to do with the objective physical condition than it does with their psychological receptivity to treatment as well as their expectations. This is the grist for the mill of the psychological evaluation and psychotherapy-related treatment process of the person with pain.
Psychological Evaluation
Because of the biopsychosocial complexity associated with pain, pain-related psychological evaluation can be helpful in cases in which symptoms are in excess of expectation or do not correlate with known physiologic processes. Psychological factors may be producing delayed recovery of function or preventing the individual from otherwise benefiting from appropriate medical treatment which, if identified, can improve the treatment process and the ultimate outcome of the case.
If psychological factors are identified as moderating or mediating the patient’s pain-related behavior, it can result in treatment recommendations that remove or ameliorate the barriers to improvement and recovery. Thus, it is thought to be helpful for treating physicians to have a basic understanding of the pain-related psychological evaluation and treatment process.
The psychological evaluation of patients with pain begins with the establishment of rapport with the individual to be assessed. In a psychology practice it is not unusual to initially encounter a patient with pain who enters the evaluation room defensively at best and offended, angry, and/or suspicious at worst. The patient with pain may interpret the pain-related psychological consultation to imply the referral source believes their problems are not real or that their complaints are psychogenic in origin. For this reason, in addition to addressing issues of informed consent and establishing rapport with the patient, there is usually a need to provide some education as to the purpose of the evaluation and how biopsychosocial variables fit into the clinical picture and subjective situation of the patient’s life.
It can be extremely helpful for the referring physician to approach the referral for a pain-related psychological evaluation in a sensitive, compassionate manner. We suggest initially explaining to patients that the dualistic view in which the mind and body are separate does not appear to hold true, and that there is a dynamic, interdependent relationship between the individual’s psyche and their physical condition. We have found it makes sense to our patients when we explain our goal to be to treat the whole person and that we want to ensure they are as psychologically and mentally fit as they can be while they are in the process of physically rehabilitating and becoming more physically fit following an injury or in treating their painful condition.
The basic purpose of the pain-related psychological evaluation is to answer the questions posed by the referral source as clearly as possible. Often, if no referral questions are forwarded with the referral, the consulting psychological examiner may need to call the referral source to clarify if there are any specific issues that need to be addressed in the evaluation. Another goal of the evaluation is to generate psychological and behavioral information that is helpful to the referral source in understanding the psychological issues in the case and promotes the care in a more efficient and effective manner. The psychological evaluation documents and preserves a record of the assessment for use in the future and may provide a baseline or outcome information regarding progress. Ultimately, appropriate diagnosis leading to specific, practical, and functional recommendations that advance the patient’s care in a meaningful way become the goal for appropriate evaluation.
To achieve the purposes of the evaluation, sufficient records need to be gathered and reviewed to provide an understanding of the medical issues and physiologic underpinnings of the case. A comprehensive clinical interview is necessary to elicit historical information about the onset and history of the pain, injuries, and background that may be psychologically contributing to the onset, severity, exacerbation, or maintenance of the pain. Opportunities for behavioral observation when the patient may or may not be aware he or she is being observed provide excellent data regarding the consistency of subjective complaints. Psychological testing can provide data derived from standardized samples of behavior that are quantifiable and illustrate how the individual being evaluated deviates from a normative base related to the concepts that are being assessed.
The clinical interview in these cases tends to be comprehensive in nature and covers important factors that can serve as potential barriers to recovery. Important topics for the clinical interview should likely include an understanding of the person’s cultural and ethnic background, because various cultures deal with issues of pain differently. The individual’s own personal and familial history of mental health problems should be explored to include issues of depression, anxiety, problems dealing with reality, and substance use. How the patient may have previously dealt with illness and injury may shed light on their ability to cope or the models for coping they may have witnessed in the past.
The individual’s cognitive capacity, level of intellectual functioning, ability to understand the nature of their condition, treatment options, and likely outcomes are important features to understand because they have bearing on how compliant, anxious, depressed, and motivated the individual may be in completing their treatment regimen. Contemporaneous stressors that the person may be experiencing in addition to their injury, illness, or painful condition for which they are being assessed will be important to explore to evaluate how taxed their resources are and also may provide necessary information regarding potential sources of secondary gain that may be promoting abnormal illness behavior.
The exploration and history obtained during the psychological clinical interview should likely also provide information about spousal availability or family solicitousness that may be unnecessarily reinforcing pain behaviors. Work history, prior work-related injuries, job changes or losses, and job dissatisfaction are important variables to survey as such factors may be either pressuring and propelling the person toward or repulsing them from relinquishing the disabled role and maintaining symptoms.
An awareness of issues involving litigation, finances, and availability of disability compensation can be important to understanding prolonged disability. Other significant pieces of psychosocial history that should be explored include the individual’s educational achievement, military service record, marital or relationship background, legal history, substance use patterns and habits, history of abuse, and available support systems.
The pain-related psychological evaluation must adequately cover the full range of issues that have bearing on the individual’s behavior. These will typically include affective disturbances, anxiety disorders, psychotic features, characterologic pathology, somatoform presentations, substance use factors, and magnified or feigned symptoms. Because the expanse of this evaluation casts a broad net, it is not unusual for such an evaluation to be composed of multiple psychological measures.
Screening versus Objective Personality Tests
One may also use a stepwise approach to psychologically pain-related evaluation that proceeds from global indices of emotional distress and disturbance to a more detailed evaluation of the most important interactive factors of the diagnosis that may include Axis I clinical disorders and Axis II personality disorders. There are two basic types of psychological instruments that can provide useful information when working with pain patients: screening tests and objective personality tests. Some screening tests can assist persons in describing, characterizing, and quantifying pain. Other screening tests can be used to identify conditions that may complicate the course of treatment and need further treatment or evaluation. However, screening tests are typically overly sensitive, are obvious in their intent, and lack validity measures. The advantages of screening tests include: they are inexpensive, quick, and patients typically understand their purpose. Objective personality tests can provide a broader, more detailed evaluation of a patient’s functioning, but they are lengthy and require specialized training to interpret. Objective tests have greater validity and reliability than screening tests.
Pain Rating Scales
There are a number of different pain rating scales in use, many of which have been modified for a specific type of clinical setting (orthopedic, rheumatology, oncology, etc.) or specific type of problem (headache scale, neck scale, low back pain scale, etc.). The simplest and most widely used is the Numerical Pain Rating Scale (NPRS) which asks patients to rate their pain from 0 to 10 with 0 indicating no pain and 10 indicating maximum pain. In some instances, clinicians will ask the patient to rate their worst pain level and best pain level in the last 30 days, as well as a range of their typical pain level. A pain level of 6 with one patient is not the same as a 6 with another patient because some are more stoic and others more catastrophizing. However, it does allow for some degree of comparison of a single patient over time. Many physicians and therapists will list the Numeric Pain Rating on each contact note to facilitate comparison over time.
Visual Analog Scale
The Visual Analog Scale (VAS) is a 10 cm line with anchor statements on the left (no pain) and on the right (extreme pain). The patient is asked to mark their current pain level on the line. They can also be asked to mark their maximum, minimum, and average pain. The examiner scores the VAS by measuring the distance in either centimeters (0 to 10) or millimeters (0 to 100) from the “no pain” anchor point. The scores tend to correlate with numerical ratings but some researchers have suggested the Visual Analog Scale is more sensitive to minor changes in pain because it can be measured in millimeters and therefore demonstrate pain changes from 47 to 53, which would both be a 5 on the Numeric Pain Rating scale. However, there is no research to support that the Visual Analog Scale is any more accurate when measured in centimeters than it is when it is measured in millimeters nor is there any research on what would represent a reliable change on the VAS. This suggests that the difference in the example between a 47 and 53 is probably not significant and is appropriately viewed as equivalent pain ratings.
FACES Pain Rating Scales
The Wong-Baker FACES Pain Rating Scale and Faces Pain Scale- Revised (FPS-R) were both developed to assist children in rating pain. They both show six faces in different degrees of distress. The FACES scale starts at 0 with the statement “No Hurt” under a face with a broad smile and continues to 5 with the statement “Hurts worst” and a face with a frown and tears. The FPS-R is similar but the point totals increase in increments of 2 instead of 1 (0 to 10). The FPS-R does not include tears on the faces because they do not want to contaminate the pain rating with an emotional rating. Both scales have been used successfully and are preferred over the NPRS and VAS with children.
McGill Pain Questionnaire
The McGill Pain Questionnaire (MPQ) is a list of 78 words divided into three domains (Sensory, Affective, and Evaluative) and 6 words for current pain intensity. While the validity of the domains and the MPQ has been called into question by some researchers it continues to be one of the most extensively used pain measures in research and clinical practice. While the quantitative value of the McGill is open for debate the qualitative value is clear. Melzack identified and organized the lexicon of pain in a manner that made it accessible to patients and professionals. Within the three domains are a total to 20 subcategories each containing from 3 to 6 descriptive words. The first domain (sensory) containing subcategories 1 to 10 includes 42 descriptors; the second domain (affective) containing subcategories 11 to 15 includes 14 descriptors; the third domain (evaluative) containing subcategory 16 includes 5 descriptors; and subcategories 17 to 20 are miscellaneous items that contain 17 descriptors. Each subcategory receives a numeric score equal to the rank order of the highest descriptor chosen. For example subcategory 1 includes the following words with the numeric value in parentheses: Flickering (1), quivering (2), pulsing (3), throbbing (4), beating (5), and pounding (6). Subcategory 2 includes the following words with the numeric value in parentheses: Jumping (1), flashing (2), and shooting (3). If the patient identifies “pulsing” and “shooting” each subcategory would have a numerical value of 3 despite “pulsing” being the third of six choices and “shooting” being the third of three choices. The subjective ordinal nature and varied number of items in the subcategories decreases the psychometric soundness of the MPQ. Likewise, the sensory domain has a range of scores from 0 to 42, the affective domain has a range of scores from 0 to 14, the evaluative domain has a range of scores from 0 to 5, and the miscellaneous items can account for 0 to 17 points. As a result of the varied relative contribution of each domain they are not able to be directly compared in a quantitative manner. The domains and miscellaneous items are summed to determine the Pain Rating Index (PRI) and another set of 6 descriptors is provided to identify the Present Pain Index (PPI). Despite the statistical limitations of the MPQ the Pain Rating Index (PRI) and Present Pain Index (PPI) do appear to have high clinical and research utility. They can provide an ipsative comparison for each patient in a test-retest format and allow for a quick point of reference on each patient contact if the PPI is used alone. The descriptors provide an inclusive lexicon of pain quality which makes communication between patient and clinician more accurate and can aid with identifying pain etiology. However, the complexity of the terms can be a problem for patients of lower IQ and other measures should be used in cases of below average IQ.
The MPQ short-form is a modified version that provides a brief (2 to 5 minutes) alternative to the MPQ (10 to 15 minutes). It consists of 15 descriptive words taken from the MPQ subcategories with a Likert scale of 0 to 3 next to each word. The 15 descriptors consist of 10 words and 1 set of combined descriptors (Hot-Burning) from the Sensory Domain and 2 words and 2 sets of combined descriptors (Tiring-Exhausting and Punishing-Cruel) from the Affective Domain. The possible range of scores is 0 to 45. The MPQ short-form also includes the Present Pain Index (PPI) and a Visual Analog Scale (VAS). The short-form has been shown to have high correlations with the original McGill Pain Scale.
Oswestry Low Back Pain Disability Questionnaire
The Oswestry Low Back Pain Disability Questionnaire (ODQ) is a 60 item patient questionnaire which assesses the amount of restriction pain imposes on 10 domains (Pain Intensity, Personal Care, Lifting, Walking, Sitting, Standing, Sleeping, Sex Life, Social Life, and Traveling). The Revised version of the ODQ replaced the domain Sex Life with the domain Changing Degree of Pain. While the test items have an average Flesch-Kincaid Grade Level of 5.3 the instructions are written at a Flesch-Kincaid Grade Level of 11.7. Consequently it is important to read the instructions to patients with limited reading skills and to make sure they understand the instructions. Both versions are administered and scored the same way. The patient is asked to identify which of six statements in each domain applies to them at the time of evaluation. The sentences are arranged from no impairment (0) to maximum impairment (5). The scores for each domain are added together (range from 0 to 50) and multiplied by 2 which yields a Disability Index Score percent. If not all items are completed, the score is prorated by averaging the items completed and then multiplying it by 10. A Disability Index Score of 0% to 20% equals minimal disability, 21% to 40% equals moderate disability, 41% to 60% equals severe disability, 61% to 80% equals crippled, and 81% to 100% indicates a patient that is either bed-bound or exaggerating their symptoms. Scores greater than 40% suggest a more detailed investigation is warranted.
Other Screening Tests
Screening tests that are helpful in dealing with patients with pain-related disorders include not only those that directly address pain but also those that screen for conditions that frequently co-occur in pain patients or can complicate the patent’s course of treatment. This can include mood disorders, anxiety disorders, personality traits, and substance-related disorders.
Beck Depression Inventory
Common screening tests of depression include the Beck Depression Inventory (BDI), Zung Self-Rating Depression Scale (SDS), and Hamilton Depression Rating Scale (HAMD). The Beck Depression Inventory has been used since 1961 and is the most common depression screening instrument. The second edition was published in 1996 (BDI-II) and represents a revision that is more consistent with current diagnostic criteria for depression. The BDI-II consists of 21 items, for example, sadness, pessimism, worthlessness. All items, except two, have four statements of increasing intensity within the domain. For example under sadness the items start with “I do not feel sad.” and end with “I am so sad or unhappy I can’t stand it.” The first item has a score of 0 while the fourth item has a score of 3. The two items evaluating changes in sleeping patterns and changes in appetite have seven total statements, one with a value of 0 indicating no change and two items each for values 1, 2, and 3 indicating mild, moderate, and severe problems (both decreased and increased sleep and decreased and increased appetite). The range of possible scores is 0 to 63. BDI-II scores are classified as minimal (0-13), mild (14-19), moderate (20-28), and severe (29-63). The strength of the BDI-II is the ease of use, wide age range (13 years and older), low reading level (average Flesch-Kincaid Grade Level 3.6), and substantial body of research. The weaknesses of the BDI-II are typical in screening measures: no validity scales and high face validity allows persons to easily manipulate the total score.
Zung Self-Rating Depression Scale
The Zung Self-Rating Depression Scale (SDS) consists of 20 items with a Likert type scale after each item. The scores for each item range from 1 to 4 and the SDS ranges from a raw score of 20 to a raw score of 80. Some items are reverse scored (i.e., they go from 4 down to 1). It has not been as well researched as the BDI-II but has been used in clinical trials of antidepressant medications. It was developed in 1965 and had not been updated. The reading level is even lower than the BDI-II (average Flesch-Kincaid Grade Level 2.2). SDS scores are classified as normal (<50), mild depression (50 to 59), moderate to marked major depression (60 to 69), and severe to extreme major depression (>70). The raw score can be converted to an SDS Index score by multiplying the raw score times 1.25.
Hamilton Depression Rating Scale
The Hamilton Depression Rating Scale (HAMD) is completed by the clinician as opposed to the patient. It consists of 17 items with Likert scale of either 0 to 4 or 0 to 2. Scores can range from 0 to 54. The HAMD was developed in 1957 and has been used extensively within the medical community but is not typically used by psychologists. HAMD scores correlate well with BDI-II scores and can be used in place of a self-report when a patient is unable to read. It can also be used when there are concerns about the accuracy of the patient’s self-report. HAMD scores are classified as normal (<9), mild depression (10 to 13), mild to moderate depression (14 to 17), and moderate to severe depression (>17).
Beck Anxiety Inventory
The Beck Anxiety Inventory (BAI) consists of 21 items with a Likert scale ranging from 0 to 3 and raw scores ranging from 0 to 63. It was developed in 1988 and a revised manual was published in 1993 with some changes in scoring. The BAI scores are classified as minimal anxiety (0 to 7), mild anxiety (8 to 15), moderate anxiety (16 to 25), and severe anxiety (30 to 63). The BAI correlates highly with the BDI-II indicating that although the BAI may provide useful clinical information, it is not specific and can’t be used diagnostically. The reading level is even lower than the BDI-II (average Flesch-Kincaid Grade Level 2.3. Because the instructions for the BAI are written at an 8.3 grade level, oral instructions should be given to persons with lower reading skills.
Substance Abuse Subtle Screening Inventory
Substance abuse screening tests can provide useful information when working with patients with a history of alcohol or substance abuse. The Substance Abuse Subtle Screening Inventory—Third Edition (SASSI-3) includes a set of obvious items asking about drug use and alcohol use. If the person is unwilling to openly acknowledge excessive alcohol or drug use, there are other scales that can assist in evaluating possible abuse/dependence. The SASSI-3 includes the following scales: Symptoms (SYM), Obvious Attributes (OAT), Subtle Attributes (SAT), Defensiveness (DEF), Supplemental Addiction Measure (SAM), Family versus Control Measure (FAM), Correctional (COR), and Random Answering. The defensiveness and random answering scales are rudimentary validity scales. There is a decision tree that assists with diagnostic impressions.
Objective Personality Tests
A more comprehensive evaluation can be completed by a psychologist using objective personality tests. These tests must be interpreted by a psychologist and can provide significant information useful in the diagnosis and treatment of the patient with pain. The most commonly used and thoroughly researched objective personality test is the Minnesota Multiphasic Personality Inventory which is currently in its second edition (MMPI-2). There is also a recently published somewhat shorter restructured form (MMPI-2-RF) based on the MMPI-2. The Personality Assessment Inventory (PAI), Millon Clinical Multiaxial Inventory—Third Edition (MCMI-III), and Millon Behavioral Medicine Diagnostic (MBMD) are other less frequently used objective personality measures that can provide valuable information.
Minnesota Multiphasic Personality Inventory
The MMPI-2 is the most widely used and heavily researched psychological test in the United States. Originally developed in the late 1930s and revised in 1989, it currently consists of 567 true/false questions. The MMPI-2 items make up a number of scales including 10 standard validity scales, 10 clinical scales with 28 subscales, 18 supplemental scales, and 15 content scales. The MMPI-2 can be administered to patients 18 years and older and requires a 6th grade reading level. The adolescent version (MMPI-A) is administered to persons 14 to 18 years of age and is similar to the MMPI-2, but is not nearly as well researched. The MMPI-2 is used in medical, psychological, employment, and legal settings.
The MMPI-2 is valued as much, if not more, for its validity scales than it is for the clinical information that can be derived from it. The first validity scale addresses the number of items omitted, and is the raw score of items which have not been answered as either true or false. If the patient fails to complete too many items, it may invalidate the profile. The validity scales include measures that evaluate if the patient is nonresponsive to questions. This could be due to acquiescent (yea saying) or counter-acquiescent (nay saying) response sets as measured by the True Response Inconsistency (TRIN) scale. It could also be due to inconsistency between items of similar content as measured by the Variable Response Inconsistency (VRIN) scale. Elevations on either scale could be due to reading problems, motivational problems, or haphazard response sets. In cases of marginal elevations on VRIN, the data are viewed as less reliable and interpretation of elevated scales is more cautious.
Validity scales that suggest underreporting of pathology include scales in which a person is trying to present an overly virtuous image (L), a guarded presentation (K), and a highly confident/competent self-presentation (S). When these underreporting scales are elevated, it typically reflects minimization of symptoms. While this does not typically invalidate the MMPI-2, it can lead to a suppression of symptoms to the point that there are no clinically meaningful elevations on the test.
Validity scales that suggest overreporting of pathology include a series of scales that are composed of infrequently endorsed items. These are low base rate items which are primarily vague or nonspecific symptoms. Elevations indicate the patient is endorsing an inordinate number of these low base rate symptoms. These scales include the Infrequency Scale (F), Infrequency Back (Fb), and Infrequency Psychopathology (Fp). The F and Fb are similar scales but F items occur on the first 370 items and include more chronic symptoms, whereas Fb items occur after item 280 and include more acute symptoms. Elevations on the F and/or Fb scale can be due to any or all of the following reasons: (1) random or fixed patterns of responding which would lead to elevations on VRIN and TRIN, respectively; (2) accurate descriptions of severe psychopathology; and (3) purposely overreporting symptoms. While VRIN and TRIN can help rule-out random or fixed patterns of responding, it is more difficult to differentiate between severe psychopathology and purposeful overreporting of symptoms. The Fp scale was developed to assist in this determination. The Fp scale is composed of low base rate symptoms in an inpatient psychiatric population. The Fp scale is less sensitive than F to the presence of severe psychopathology.
The Fake Bad Scale (FBS) is described as having been devised to detect a model of goal directed behavior with a focus on appearing to be honest; appearing psychologically normal, except for the influence of the alleged cause of injury; avoiding admitting to preexisting psychopathology; where preexisting complaints are known, or suspected to have been disclosed to the examining clinician, attempting to minimize those complaints; hiding preinjury behaviors that are antisocial, illegal, or minimizing it if it appears the behaviors will be discovered independently; and presenting an extent of injury or disability within a perceived limit of plausibility (Lees-Haley, English, Glenn, 1991). The FBS continues to be a controversial scale, but the publisher of the MMPI-2 has recognized the FBS as a reported scale and includes it in the standard MMPI-2 report. By using the more conservative cutoffs of raw scores (24 for males and 26 for females) the concern of a high false-positive rate has been minimized. The existent literature indicates that raw scores above 28 on the FBS are associated with a very low false-positive rate. Additionally, the literature suggests that increasing confidence is placed in scores as they rise above a cutoff of 30, with a number of studies noting that no nonlitigant, nonmalingering subjects had raw scores of 30 or above.
There are a number of less commonly used validity scales that are used by some researchers and clinicians. One particularly interesting additional validity scale is the Meyers Validity in Chronic Pain Index (Meyers Index) that uses a chronic pain population. The developers combined seven different validity scales on the MMPI-2 into a common weighted method in assessing malingering in chronic pain patients. This weighted method was able to correctly classify 100% of nonlitigants using a cutoff score of equal to or greater than 5. That study suggested chronic pain patients in litigation produce a different profile on the MMPI-2 validity scales than do nonlitigants. The Meyers Index is calculated by assigning values of 0, 1, or 2 on seven validity scales based on the level of elevation on each scale. The Meyers Index score is classified as okay (0 to 2), exaggerated (3 to 4), malingered (5 to 8), and clearly malingered (9 to 14). The Meyers Index uses the following scales (F, FBS, F-K, Fp, Ds-r, Es, and O-S).
Once an MMPI-2 profile has been determined to be valid, the Clinical Scales and Subscales can be evaluated to provide information about the patient’s psychological and emotional functioning. The MMPI-2 retained the same 10 MMPI clinical scales including the scale names and numbers. Some of the scale names are antiquated (e.g., Psychasthenia) and as such are typically referred to by number or abbreviation. For example scale 2 is Depression and is generally called scale 2 or the D scale. The Clinical Scales were initially developed using a method known as empirical criterion keying and as such are not based on any specific theory or diagnostic criteria. Each clinical scale is a combination of items that a specific group (e.g., depressed patients) answered differently than the comparison group.
The fact that the MMPI-2 is not tied to a diagnostic system such as the DSM or ICD is an advantage and disadvantage. The advantage is the MMPI-2 does not change each time the diagnostic criteria are changed. This allows for comparison of MMPI-2 profiles across time and facilities research. The disadvantage is that the MMPI-2 does not provide and lend itself well alone to making a DSM diagnosis. For example, an elevation on scale 2, the Depression scale, does not indicate the presence of major depression. It could be depressive symptoms due to dysthymic disorder, grief, or depressive symptoms due to recent emotional stressors such as a severe work-related injury to a patient’s spouse. Consequently the MMPI-2 cannot be interpreted effectively in a vacuum and “blind interpretation” of the MMPI-2 tends to lead to interpretive statements which include a substantial amount of error within the interpretive statements. This suggests great care needs to be taken in dealing with blind, computer-generated interpretive reports.
Interpretation of profiles from medical patients using a psychological or psychiatric comparison group can lead to erroneous interpretations and misdiagnosis. Consider, for example, compiled MMPI-2 norms for a chronic pain population using 209 chronic pain inpatients. The chronic pain patients scored significantly higher than controls on 9 of the 10 clinical scales. Traditional interpretive methods would over-pathologize the patients with chronic pain. Clinical Scales 1, 2, and 3 are the most frequently elevated scales in a chronic pain population. The typical chronic pain profile will present a “conversion V” or somatic profile. If these scales are elevated when compared with a chronic pain reference group then a somatization or conversion disorder may be present.
In addition to the Clinical Scales there are a number of other scales on the MMPI-2. Although these are less heavily researched than the Clinical Scales, they can still provide useful information. Additional scales include the Content Scales, Supplemental Scales, and Restructured Clinical Scales. The Content Scales include the following scales: Anxiety, Fears, Obsessiveness, Depression, Health Concerns, Bizarre Mentation, Anger, Cynicism, Antisocial Practices, Type A, Low Self-Esteem, Social Discomfort, Family Problems, Work Interference, and Negative Treatment Indicators. The Supplemental Scales include the following scales: Anxiety, Repression, Overcontrol-Hostility, Dominance, Ego Strength, Social Responsibility, College Maladjustment, MacAndrew Alcoholism-Revised, Addiction Admission, Addiction Potential, Marital Distress, PTSD, Gender Role—Masculine, and Gender Role—Feminine. The Content and Supplemental Scales are labeled using more contemporary labels, which typically do not require additional explanation.
MMPI-2 Restructured Form
The Restructured Clinical Scales are relatively new scales that show promise, but have not been fully evaluated in pain patients. The Restructured Clinical Scales also form the core of a new version of the MMPI-2 which is called the MMPI-2 Restructured Form (MMPI-2-RF). The MMPI-2-RF retains many of the positive features of the MMPI-2 in a shorter format, 338 items versus the 567 items of the MMPI-2. The MMPI-2-RF includes revised versions of many of the MMPI-2 validity scales, but does not include the traditional Clinical Scales. There a several promising aspects to the new MMPI-2-RF including a new validity scale that assesses for the presence of Infrequent Somatic Responses (Fs). There are also a number of problem-specific scales that focus on Somatic/Cognitive Dysfunction.
Personality Assessment Inventory
The Personality Assessment Inventory (PAI) is another objective personality measure. It is composed of 344 items with 4 possible responses for each item (False, Slightly True, Mainly True, and Very True). It consists of 22 scales including 4 validity scales, 11 clinical scales, 5 treatment consideration scales, and 2 interpersonal scales. The reading level (average Flesch-Kincaid Grade Level 4.1) is lower than the MMPI-2. There has been some research using the PAI in chronic pain settings that should increase the utility of the test. The PAI addresses psychological disorders, personality disorders, and substance abuse disorders making it a very high utility test and an acceptable alternative to the MMPI-2 in some settings. The validity scales are not as well researched as the MMPI-2, which limits its use in medicolegal settings unless used in conjunction with other symptom validity tests.
Millon Clinical Multiaxial Inventory—Third Edition
The Millon Clinical Multiaxial Inventory—Third Edition (MCMI-III) is another frequently used objective personality measure. The MCMI-III provides information about the presence of psychological disorders including personality disorders. The MCMI-III is a 175-question, true/false psychological instrument used in clinical settings with individuals 18 years and older. The reading level (average Flesch-Kincaid Grade Level 5.7) is higher than the MMPI-2.
The normative population is composed of patients seen in individual practice, clinics, mental health centers, forensic settings, residential facilities, and hospitals. The MCMI-III uses “Base Rate” scores for the purposes of reporting and interpretation. A Base Rate (BR) score of 60 [BR60] represents the median score, as opposed to T scores where 50T is the median, with BR0 being the lowest possible score and BR115 the highest. The presence of a specific personality trait is generally indicated at BR75, whereas scores of BR85 and above suggests the full presence of a personality characteristic. Base rate scores are criterion, not norm, referenced—indicating that BR scores do not indicate if a score is common or not, only whether the trait or characteristic is present.
The MCMI-III has 28 scales including 14 Personality Disorder Scales, 10 Clinical Syndrome Scales, 4 Correctional Scales. The Personality Disorder Scales include: Schizoid, Avoidant, Depressive, Dependent, Histrionic, Narcissistic, Antisocial, Sadistic (Aggressive), Compulsive, Negativistic (Passive-Aggressive), Masochistic (Self-Defeating), Schizotypal, Borderline, and Paranoid. The Clinical Syndrome Scales include: Anxiety, Somatoform, Bipolar, Manic, Dysthymia, Alcohol Dependence, Drug Dependence, Post-Traumatic Stress Disorder, Thought Disorder, Major Depression, and Delusional Disorder. The Correctional Scales include: Disclosure, Desirability, Debasement, and Validity. The Personality Disorder Scales were designed to correlate with DSM-IV Axis II disorders, whereas the Clinical Syndrome Scales correlate with the DSM-IV Axis I disorders.
Another study examined the ability of the MCMI-III to be reliably used to assess intervention in pain management at a pain management center in Paducah, Kentucky. One hundred consecutive patients were evaluated for major depression or generalized anxiety disorder using a DSM-IV-TR questionnaire and physician interview; all participants also completed the MCMI-III and P-3 inventories as part of a psychological evaluation. A positive diagnosis of major depression or generalized anxiety disorder, using the DSM-IV-TR criteria, was considered the criterion standard. The diagnosis of major depression on the MCMI-III showed 100% specificity but only 54% sensitivity; for generalized anxiety disorder, the MCMI-III specificity was 89%, whereas the sensitivity was 73%.
Millon Behavioral Medicine Diagnostic
The Millon Behavioral Medicine Diagnostic (MBMD) is a revised version of the Millon Behavioral Health Inventory (MBHI) and was designed to provide helpful information on a patients’ biopsychosocial health. The test aids in recommending potential treatment strategies and may help in proactively identifying potential pitfalls to treatment. The MBMD can be used with individuals 18 years to 89 years and requires a sixth grade reading level. Consisting of 165 true/false questions, the MBMD typically takes 20 to 25 minutes to complete. The MBMD allows the clinician to select one of two normative samples—a general medical sample and a sample of prescreened bariatric surgery patients.
The MBMD consists of 29 content scales, grouped into five domains, six negative health habits, and three scales to detect response patterns. The Content Scales include the following: 5 Psychiatric Indicators (Anxiety-Tension, Depression, Cognitive Dysfunction, Emotional Liability, and Guardedness); 11 Coping Styles (Introverted, Inhibited, Dejected, Cooperative, Sociable, Confident, Non-Conforming, Forceful, Respectful, Oppositional, and Denigrated); 6 Stress Moderators (Illness Apprehension, Functional Deficits, Pain Sensitivity, Social Isolation, Future Pessimism, and Spiritual Absence), 5 Treatment Prognostics (Interventional Fragility, Medication Abuse, Information Discomfort, Utilization Excess, and Problematic Compliance), and 2 Management Guides (Adjustment Difficulties, and Psych Referral). There are 6 Negative Health Habits (Alcohol, Drugs, Eating, Caffeine, Inactivity, and Smoking). There are 3 Response Patterns (Disclosure, Desirability, and Debasement).
Despite the success of the MBMD in assessing biopsychosocial health characteristics and treatment options, practitioners have been warned to be cautious when using the MBMD because limitations in clinical use may arise in specific populations.
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