How could the validity of the

DSM-IV pain disorder be improved

in reference to the concept

that it is supposed to identify?

Robert J Boland MD

Associate Professor of Psychiatry

and Human Behavior

Brown University School of Medicine

correspondence to:

Department of Psychiatry

The Miriam Hospital

164 Summit Avenue

Providence, RI 02906

phone: (401) 793-4300

fax: (401) 793-4312

email: robert_boland_1@brown.edu

Abstract.

This article examines the dilemmas inherent in psychiatry's attempts to incorporate pain disorders into the standard psychiatric nomenclature. Each succeeding Diagnostic and Statistical Manual has broadened the concept of pain disorders, and, gradually, the diagnosis has become increasingly removed from the original idea of "psychogenic pain." The advantage of this broadening has been the increased utility of the diagnosis in clinical settings. However, there remains a problem of validity, as the disorder continues to imply a mind-body dualism, and clinicians are asked to determine the relative contribution of both to the overall picture of pain. After examining this problem, the article looks at some alternative models, and offers some generalizations regarding the dimensions of the pain experience. The article ends by tentatively offering some suggestions for future approaches to pain diagnoses in psychiatry.

INTRODUCTION

The classification of pain as a diagnosis has been particularly vexing for psychiatry. Unlike most diagnoses currently classified in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) [1], pain is not in itself a disease. Nor does it imply specific features, common attributes or course that might qualify it to be considered a syndrome. Pain is a symptom, and as such can have a variety of etiologies and ramifications.

Even defining pain has been difficult. At it's simplest, pain is an unpleasant physical sensation, analogous to other senses. In that sense, it does not seem to be a psychiatric disorder. However, unlike the other senses, it is modulated at every level of the nervous system. In this sense, all pain disorders have psychological components. Therein lies the problem of how psychiatry should diagnose pain disorders.

PAIN AND PSYCHIATRY

Most standard textbooks of psychiatry spend little space on pain disorders. The question remains, for some, as to why pain disorders should be included among psychiatric disorders at all. There are certainly potentially disadvantages in diagnosing pain as a psychiatric illness: the most obvious is the fear that pain patients will be inadequately treated, if their pain is thought to be only "in their head."

One reason for the inclusion of pain disorders in the psychiatric classification system may be simple practicality. Psychiatrists are often called to aid in the treatment of chronic pain, and most multi disciplinary pain teams include either a psychiatrist or psychologist among their members. Psychiatric interventions, both pharmacological and psychotherapeutic, are widely used to treat chronic pain. Furthermore, there is considerable literature suggesting a high comorbidity between pain disorders and more "typical" psychiatric disorders, such as depression and anxiety.

Thus, from a practical standpoint, psychiatry cannot ignore pain. The question remains, however, as to how psychiatry should approach pain disorders. Particular pitfalls include the danger of naive "mind-body" distinctions, as well as the tension over whether to take a broad or a narrow view of pain disorders.

PSYCHIATRY'S ATTEMPTS TO CLASSIFY PAIN

DSM-I

In the original Diagnostic and Statistical Manual of Mental Disorders (DSM-I) [2], published in 1952, pain was not specifically discussed. However, there were categories included to describe physical disorders with presumed psychological etiology. One example was the "psychophysiology disorders," in which persistent states of heightened affect were believed to influence organs and viscera in a direct way, often to the point of structural changes in the organ. This direct involvement, on a physiological level, differentiated these disorders from the more common psychoneurotic disorders.

The psychoneurotic disorders, as described in DSM-I were considered to be primarily anxiety disorders. The disorder most relevant was "conversion disorder" in which anxiety was unconsciously "converted" into a physical symptom. Whereas the psychophysiological disorders primarily involved the autonomic system, the conversion disorders were thought to involve primarily organs that were under conscious control (such as the motor system), and to operate in the absence of any organic pathology.

DSM-II

The Diagnostic and Statistical Manual of Mental Disorders, Second Edition (DSM-II, 1968) [3], though making some major changes in its conception of psychiatric disorders, left its approach to mind/body interactions largely unchanged. Thus, the descriptions of the psychophysiologic disorders and conversion disorder (now termed "Hysterical neurosis, conversion type") were similar to DSM-I definitions. Pain was once again not specifically mentioned. In practice, conversion symptoms usually involved the voluntary nervous system, though the senses could be involved as well. In the case of the psychophysiologic disorders, pain would not be considered a diagnosis in itself, but rather it would be included among the symptoms affecting a specific organ system (for example, "heartburn" as part of a "psychophysiologic gastrointestinal disorder.").

DSM-III

The Diagnostic and Statistical Manual of Mental Disorders, Third Edition (DSM-III, 1980) [4] represented a radical change in psychiatry's approach to taxonomy, with the introduction of a categorical system of diagnosis. The many changes and their implications are beyond the scope of this discussion, but most relevant was its general abandonment of diagnoses that were based on presumed etiologies. Instead, disorders were defined on objective, phenomenological grounds.

DSM-III specifically included a pain disorder: "psychogenic pain disorder." The main feature of this diagnosis was severe and prolonged pain that occurred either in the absence of any organic pathology, or in excess of what would be expected from physical findings. Thus, this disorder was largely reserved for patients who had little or no physical basis for pain. Psychological etiologies were assumed by observing either a temporal relationship between psychological stress and the pain, or some mechanism of clear secondary gain from pain (avoidance of activity, enabling supports otherwise unavailable). Psychogenic pain disorder was thought to be somewhat different from the more typical somatoform disorders, and many features described in the"hysterical" disorders (for example, "la belle indifference" or symbolization of the conflict) were considered unusual in psychogenic pain.

DSM-III-R

The Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised (DSM-III-R, 1987) [5] renamed psychogenic pain as "somatoform pain disorder," and, again, it was reserved for pain patients who had little or no organic pathology. The criteria were simplified: evidence for a psychological etiology was no longer required, and diagnosis primarily based on the basis of the lack of sufficient organic pathology. As an added criterion, the pain had to be present for at least six months, thus limiting this diagnoses to patients with chronic pain.

Implied in the discussion of somatoform pain was the notion of the "pain prone patient." That is, it was felt that a certain personality type was particularly vulnerable to developing a pain disorder. This personality type was characterized by an early work history, often having physically demanding or tedious jobs, rarely taking time off. Often, despite their strong work ethic, they received little attention or recognition for their efforts [6].

Critique of DSM-III3 and -IIIR

An analysis done after the introduction of these diagnoses suggested that they were rarely used [7]. An important reason for this was thought to be the requirement that the clinician determine the etiology of a patient's pain: essentially to distinguish between physical and psychological pain. There was little guidance, however, as to how this could be done. Similarly, there was little guidance on how to determine if pain is "in excess" of physical findings. The diagnoses perpetuated a dualistic mind-body view of pain. As a result, the diagnosis had little practical value, and did not seem relevant to most of the patients seen in pain clinics, in which both psychological and medical factors appeared to have significant roles. And, though a compelling formulation, the "pain-prone" patient formulation lack validity [8], and did not appear relevant to many chronic pain patients.

DSM-IV

In response to the above and other criticisms, the DSM-IV criteria for pain disorder were dramatically changed. First, the name of the disorder itself was simplified to "Pain Disorder." In defining the disorder, the role of psychological factors in pain is generalized and broadened, and the criteria simply require that "psychological factors are judged to have an important role in the onset, severity, exacerbation, or maintenance of the pain."

Perhaps the most dramatic change in DSM-IV is in the way organic pathology is handled. For the first time, the presence of a significant medical contribution to pain is allowed. DSM handles this by creating two categories: Pain Disorder Associated with Psychological Factors and Pain Disorder Association With Both Psychological Factors and a General Medical Condition. The first category is more akin to DSM-III and -IIIR, with no medical factors thought to be related to the pain. In the latter category, both psychological factors and a general medication condition "are judged to have important roles in the onset, severity, exacerbation, or maintenance of the pain."

Critique of DSM-IV

Though greatly improved, DSM-IV defined pain disorder still leaves a number of dilemmas. A strict reading of the disorder continues to suggest a mind-body dichotomy in viewing pain. Implied in the subcategories of pain with or without medical factors is that pain can be divided on the basis of the relative contribution of psychological and organic factors. Indeed, in diagnosing Pain Disorder, the clinician must decide between not only two, but three categories, as Pain Disorder Associated with a General Medical Condition (in which psychological factors play no significant role) is included as a third, nonpsychiatric, disorder. In essence, the clinician must determine the relative contributions of mind and body to the presentation of pain. Little guidance is given in the volume as to how this can be done.

CURRENT USE OF THE PAIN DISORDER DIAGNOSIS

Clinical settings

Informal surveys of the use of this disorder within chronic pain clinics suggest that the philosophical dilemmas posed by the disorder have largely been ignored. In centers in which psychiatry does not play a significant role, the disorder is rarely used, and alternative diagnostic schemes employing medical terminology are favored [9]. In centers where psychiatry and psychology do play a role, the disorder is more common. Primarily used is the subcategory of Pain Disorder Associated with both Psychological Factors and a General Medical Condition. Superficially, the diagnosis seems reasonable in that most patients generally do have a combination of both psychological and medical factors contributing to their pain. In fact, as stated by the Subcommittee on Taxonomy of the International Association for the study of Pain, pain is never merely nociception, and "is always a psychological state." Viewed this way, all pain is associated with psychological factors and a general medical condition. However, by making this diagnosis all inclusive, there is a risk of rendering it useless. In encompassing all pain patients, there seems to be no clear way to distinguish the cases that are of particular psychological concern, and the decision to use a psychiatric diagnosis appears to be a subjective one, dependent on the philosophy of the diagnostician [10].

Research settings

As already noted, one of the critiques of previous DSM pain disorders was their lack of use in research settings. Reviewing studies since DSM-IV, this problem seems to remain. There continue to be a paucity of studies examining Pain Disorder as an entity. Most chronic pain studies continue to use alternative nomenclature. When they do employ psychiatric disorders, the tendency continues to be the study of comorbid major psychiatric disorders ( such as depression and anxiety) in the setting of chronic pain. The majority of articles extant examining DSM-IV as an entity tend to be critical of it, noting its continued reliance on mind-body dualism [11]. Studies examining the utility of DSM-IV Pain Disorder have found little evidence that justified the subtypes proposed. In fact, available data implies the opposite, and it appears that patients who are placed in either the psychological or psychological plus general medical subtypes of the disorder do not differ on such measures of pain as duration, intensity, or type, nor do they differ on measures of disability [12]. Other research has questioned the sequestering of "pure" pain disorder from pain that is associated with other somatoform disorders [13].

OTHER APPROACHES TO PAIN

The International Association for the Study of Pain (IASP) [14] suggests the use of a five-
axis system for categorizing chronic pain. The axes are as follows: I. Anatomical region, II. Organ system, III. Temporal characteristics of pain and pattern of occurrence, IV. Patient's statement of intensity and time since the onset of pain, and, V. Etiology.

This system is primarily focused on the physical dimension of pain. There is room in the system for suggesting a psychological role in pain, specifically in the second and fifth axises. Psychogenic pain was defined by the IASP as "Pain specifically attributable to the thought process, emotional state, or personality of the patient in the absence of an organic or delusional cause or tension mechanism." Such a system hardly seems an improvement, as one is still forced to choose between psychological and physical factors.

A number of pain scales and instruments have been devised to measure various aspects of pain. Some of the most familiar scales, such as visual analogue scales, or numerical ratings scales [15] measure the patient's sensory perception of pain, concentrating on the intensity of the perception. Other scales, such as the Descriptor Differential Scale [16] and the Pain Perception Profile [17], broaden the perceptual experience, measuring not only intensity, but the affective component of pain.

Other scales go beyond perceptual qualities, and look at such domains as behavioral aspects of pain, or the impact of pain on a patients life. These tend to be larger, multidimensional scales. For example, the American Pain Society's Patient Outcome Questionnaire [18] looks not only at pain severity, but the patient's reports of the affect of pain on his life, and the patient's reports of satisfaction with treatment. Similarly, the Emory Pain Estimate Model [19] looks both at physical dimensions of pain as well as pain associated behaviors. The West Haven-Yale Multidimensional Pain Inventory [20] classifies both physical and psychological variables. The primary psychological dimension related to the patient's response to pain, and their ability to cope with it. Some scales also focus on more interpersonal dimensions, such as the Unmet Analgesic Needs Questionnaire [21], which investigates a patient's dissatisfaction with their pain treatment.

THE DIMENSIONS OF PAIN

To summarize the above, most attempts to classify pain usually focus on one aspect of the pain. Most of the instruments designed to measure pain are concerned not so much with diagnosis, but with clinical characterization of a specific pain-related problem. A classification system, to be truly valid, will have to incorporate the different dimensions of the pain experience.

One can debate as to what the exact dimensions should be, but, in reviewing the discussion above, there are at least three dimensions of factors in the pain experience: the etiological basis for the pain, the patient's perception of the pain, and their presentation of the pain experience to others. Describing these in more detail:

Objective/Physical etiology

For most patients complaining of pain, we assume that behind the complaint is some physical process is "going on inside." Such a statement is not meant to revisit the mind-body distinction–even psychological processes must, in the end, have a physical basis in order for them exert an effect on an individual. However, there are at least, two limitations to the understanding of pain etiology. First, there is no direct measure or test for pain, and there is no objective way to associate it with observable pathology. Second, even if we could determine the physical etiology behind a pain complaint, this would not, in itself fully explain the pain experience. In fact, we know that the opposite is true–even when the cause of pain is clear (e.g., experimentally produced pain) the relationship between the energy of the cause and the end perception is not linear.

Perception

Beyond the physical reality of the pain, there is considerable variation in how patients experience nociception. This perception is influenced by a number of factors, for example, timing, context, perceived meaning, cognitive and emotional state at the time.

Presentation

One cannot neglect the interpersonal aspects of pain. Part of the pain experience involves the way an individual expresses their pain to the rest of the world. This expression can be nonverbal, as in pain-related behaviors, or verbal. They may or may not be consciously produced. Pain presentations are not only determined by the patient himself, but by those that receive the presentation. As with all observations, the observer affects the observed.

When one considers a patient with a pain disorder, one can describe them in terms of these dimensions. Viewed graphically (see FIGURE) one can imagine patients as falling somewhere in a three-dimensional space. All patients present with some variability on each axis, however the patients that are seen as more "psychological" or "problem patients" are those that deviate more preferentially on one or more axes. Such a model eliminates the dilemma of having to choose between mind and body; instead we would consider the relative interactions of these different dimensions.

USING A DIMENSIONAL SYSTEM

Once applied, a dimensional approach allows one to capture the myriad of difficult and different problems that present to a chronic pain clinic. For example:

Patients with comorbid depression or anxiety

As already noted, the presence of a comorbid major psychiatric disorder can influence patients in a variety of ways. Depressed patients certainly can have exaggerated presentations, in that their overall misery will affect their expression of somatic events. Depression may even cause pain, though this is probably rare. The opposite effect, in which depression is secondary to chronic pain, is probably more common. However, depression and other psychiatric disorders most likely exert their strongest influence on the patient's perception of pain. Patients with depression, for example, appear to be more sensitive to painful sensations, and less apt to respond to pain treatments. That this should be true in not surprising, as depression can so adversely affect many physical functions (sleep, appetite, energy). In classifying comorbid disorders in this way–how they affect the pain problem, rather than issues of causation–it may be possible to better capture problems facing the treatment of the many pain patients with comorbid psychiatric disorders.

Patients with hypochondriacal symptoms

In DSM-IV, patients whose pain complaints can be better explained by another somatoform disorder are preferentially classified as having that other disorder. However, hypochondriacal symptoms occur as a spectrum of complaints, and many chronic pain patients who clearly have good "objective" reasons for pain will express hypochondriacal ideations. Some patients may become overly preoccupied with the "meaning" behind their pain, and may undergo unnecessary procedures in the vain hope of "getting to the bottom" of their pain. Ultimately, this pursuit for unobtainable explanations can be frustrating to both the patient and their clinician. Once again, though these patients are not truly hypochondriacs per se ( in that one cannot say that their physical concerns have solely a psychological basis), their preoccupation with disease can cause considerable discomfort independent of the pain. Analogous to theories about hypochondriasis, the basis of such behaviors can be seen as a perceptual disorder, in that patients are either misperceiving painful sensations, or overintepreting them [22].

Patients with somatization symptoms

Using an argument similar to that for hypochondriacal patients, some pain patients who are seen as "psychological" fall more into a somatization-type spectrum. These are the patients who are seen as "constantly complaining," and never happy with partial improvement. Often, the level or frequently of their complaints is such that they are mistaken for malingerers (e.g., "medication-seekers"). A more useful way to view such patients may be to view them as "presentation disordered" in which the very manner of their intercourse is outside the norm. This is analogous to theories of somatization disorder as a type of communication disorder, which is often seen in the oppressed or neglected who cannot communicate in more practical ways [23].

Malingering

True malingering is not a psychiatric disorder at all. Frankly put, malingering is simply lying, and represents human frailty rather than psychopathology. It may be associated with psychopathology (e.g., personality disorders), but it need not be. True malingering, being not a disorder, cannot have a treatment. Therefore, if a patient is thought to be a malingerer (ex. making up a pain complaint for the purpose of obtaining opioids), there is no course except to refuse any intervention.

However, malingering-type behavior, for example purposefully exaggerating one's pain symptoms in order to ensure maximal care, is probably not at all uncommon, nor is it limited to patients whom we would consider "antisocial." The fact that a patient exhibits more pain behaviors when observed than when alone can be understood, interpersonally, as "normal" social behavior. That is, to understand such seemingly "manipulative" behavior, one must first consider what effect observation is having on the patient. As distraction tasks are often used to keep one's mind off of pain, it is reasonable to think that focusing on a patient's pain (as in a medical encounter) will bring out symptoms. It is preferable to try and avoid an "either-or"stance toward what appear to be intentional exaggerations of truthful reporting, and instead attempt to understand the factors in the doctor-patient relationship (for example) that could influence a patient's presentation. In this sense, most malingering-type behaviors can be incorporated into one's understanding of the whole patient.

Factitious disorder

Similar to the discussion of malingering, some patients will purposefully fabricate pain symptoms for the sole purpose of assuming the patient role. Factitious disorder, or Munchausen's syndrome, in its pure form, is a severe psychiatric disorder that requires intensive, specialized treatment. However there are surely many patients with chronic pain, who, though not having symptoms to the degree that they would be classified as having a true factitious disorder, may feel some gain in assuming the patient role, which can be reinforcing in itself. Often, a rather heavy handed approach is taken toward such patients, with the notion being expressed that a patient is exaggerating their condition for the purpose of "secondary gain." In fact, one can argue that secondary gain is a ubiquitous motivation for all humans. Instead, we should be interested in the particular types of secondary gain a patient desires, and the manner in which they try to obtain them. In the case of factitious-type disorder, one would want to incorporate a patient's relative desire to assume the sick role as part of the dimension of their presentation.

"True" psychogenic pain

Are there ever cases in which pain is entirely of psychological etiology? Clearly, the original diagnosis of psychogenic pain was meant to describe such a condition, however the lack of application of this disorder in real work setting lead to the above-mentioned changes in the disorder. The rarity of the disorder does not change the fact that there are some cases in which patients seem to be truly perceiving themselves as having pain, presenting their pain as accurately as they can, but for whom there seems to be no physical cause for the pain, and there is evidence for a psychological cause. This description of psychogenic pain, of course, seems analogous to a description of a conversion disorder. DSM-IV Conversion Disorder specifically excludes pain as a sole symptom in conversion patients. However, the purpose of this distinction seems less one of theory, and more one of taxonomy, in that such patients would now be encompassed by the diagnosis of Pain Disorder. However, as discussed above, the various iterations of pain disorder in DSM have increasingly evolved beyond the original notion of psychogenic pain, and there seems less and less reason to exclude pain as a potential conversion symptom.

Such controversies, however, would not be present in a dimensional system, in which psychogenic etiologies could be incorporated into the etiological dimension. The problem of how one could ever truly distinguish this disorder is unresolved, thus it is expected that the concept will continue to be rarely invoked in clinical settings.

FORMULATING TREATMENT PLANS WITH A DIMENSIONAL SYSTEM

The clearest advantage of a dimensional understanding of pain is in treatment formulation. Are there ever cases in which somatoform pain should be treated with traditional pain medications? Such questions would be irrelevant under a dimensional system that considers both organic and psychological factors as part of the pain experience.

In making decisions about medication, one would consider the likely etiologies of the pain, and treat accordingly. However, this is clearly not enough for many pain patients, particularly those with chronic pain. For patients with clinically important perceptual factors, additional treatments would be important as well. For example, treatment of a comorbid mood disorder would be part of the treatment plan. Once again, "either-or" approaches to treatment could be avoided–one need not decide between treating pain and depression, nor does one need to have unrealistic hopes that treating a mood disorder will successfully address the entire pain problem.

Similarly, patients who seem to have a strong hypochondriacal component would have this addressed either through psychoeducation or behavioral techniques to help them better evaluate their internal perceptions. In the case of presentation disorders–whether they are of the unconscious, or deliberate type–the clinician will have to attempt to understand how and what they are communicating. In the case of the somatization-type behaviors, this may argue for broader psychosocial interventions to address other sources of stress or dysfunction in their lives. In the case of the deliberate disorders, this may indicate a breakdown of the doctor-patient relationship ("you aren't taking me seriously, so I have to compensate by exaggerating"). In such cases, the reestablishment of a trusting relationship with mutually agreed goals is paramount, and all other types of treatment are likely to fail until this is addressed.

CONCLUSION: RECONCILIATION OF DIMENSIONAL MODELS WITH DSM'S CATEGORICAL SYSTEM

Since DSM-III, psychiatric taxonomists have clearly wished to avoid dimensional approaches to diagnosis, as they tend to be neither valid not reliably. This is unlikely to change, and there are many good arguments for DSM continuing to embrace a categorical approach to diagnosis. However, in the case of pain disorders, the use of a categorical approach, combined with the broadening of the diagnosis to encourage use, makes it conceivable that the true spectrum of pain disorders will never be adequately encompassed by psychiatry. Once again, pain is not in itself a disease, but rather a symptom. Chronic pain is a syndrome, with numerous causes and manifestations and cannot be described by a single diagnosis.

One could argue that psychiatry need not capture all of the clinically important pain disorders. Though all are psychological in a sense, many may not rise to the level of being "psychiatric disorders." Perhaps DSM should capture only the subset of pain disorders that have the most prominent psychological symptoms. In a sense, this is what DSM originally tried to do, but the broadening of the diagnosis in the interest of utility has distanced it from this original concept. However, this same broadening has had the benefit of making the diagnosis somewhat more applicable to the pain patients most commonly seen.

It may that psychiatry cannot have it both ways. Either the diagnosis should be further broadened to encompass all pain patients, with the attempt at distinguishing psychological versus medical influences be dropped. Alternately, the disorder could be narrowed to include only the patients originally intended by the concept of "psychogenic pain." The remainder of pain patients, albeit the majority, would be then returned to the province of general medicine.

Categorical systems tend to cause such "all or none" choices. There are alternatives. DSM has many precedents for the idea of collapsing dimensional models into convenient categories. For example, depression, presumably a dimensional disease with a variety of symptoms, severities and longitudinal courses, has been collapsed into relatively few diagnoses: (1) major depression, with three levels of severity and four possible courses and (2) dysthymia. In the appendix of DSM can be elements of a larger dimension of mood disorders (including minor depression and brief recurrent depression) however these are not yet generally accepted in US nomenclature. This is true despite considerable literature attesting to the existence and disability caused by more minor forms of depression.

One can imagine a similar collapsing of the dimensions of the pain disorder. These could be based on a patient having a comparably major deviation on one or more axis: thus there would be patients for whom the primary disorder was in etiology (for example, psychogenic pain patients), those who had primarily disorders in the ability to perceive pain (comorbid disorders, hypochondriacal-type pain disorders) and those with presentation-type disorders (which would include somatoform-type disorders, and patients with malingering-type behaviors ). One could also imagine combinations of these, but the cumbersome number (27) of categories would argue for field studies to define which are most clinically relevant.

FIGURE

REFERENCES