When a patient seeks treatment from a health care provider because of a symptom such as pain, the initial focus is on the patient’s medical history and the underlying pathology—a hunt to identify the broken body part, which is treated to eliminate the symptom. In chronic diseases there may be no cure currently available and the best that can be accomplished is alleviation of the symptoms. However, it is important to maintain a longituidinal perspective that a patient with symptoms has a learning history that existed before the onset of the symptoms, as well as contextual factors that are present throughout the course of the medical condition. Both will have important influence on how symptoms are experienced and how the patient adapts to the symptoms and responds to treatment.
Chronic pain, like many chronic diseases, is a demoralizing state that confronts individuals not only with the distress created by the symptoms but also with many other ongoing difficulties that compromise all aspects of their lives. Living with chronic disease requires considerable emotional resilience because it depletes people’s emotional reserves. Individuals with chronic pain have a continuing quest for relief that often remains elusive; this can lead to feelings of demoralization, helplessness, hopelessness, and outright depression.
It is also important to keep in mind that most people do not live in isolation but within a social context. Thus, chronic symptoms tax not only the individual but also the capacity of significant others who provide instrumental and emotional support. Health care providers share patients’ and significant others’ feelings of frustration as reports of symptoms continue despite providers’ best efforts and at times in the absence of pathologic signs that can account for the symptoms reported.
In chronic pain syndromes (e.g., osteoarthritis, fibromyalgia, diabetic painful neuropathy), the pain does not appear to have any obvious useful function. Pain that is chronic can significantly compromise quality of life and, if unremitting, may actually produce physical harm by suppressing the body’s immune system. Historically, a number of models have been postulated to explain chronic pain. Several are outlined below.
Biomedical Model of Chronic Pain
The traditional biomedical model of pain—which dates back to the ancient Greeks and was inculcated into medical thinking and practice by Descartes in the 17th century—assumes that people’s reports of pain result from a specific disease state represented by disordered anatomy and physiology. The diagnosis is confirmed by data from objective tests showing physical damage and impairment, and medical interventions are specifically directed toward correcting the organic dysfunction or organic source of pathology.
Health care providers often undertake Herculean efforts (frequently at great expense to the patient or third-party payer) in an attempt to establish the specific link between objective indications of tissue damage and the reported severity of pain. The expectation is that once the physical cause has been identified, appropriate treatment will follow. Treatment will then focus on eliminating or blocking the putative cause or causes of the pain by chemical (e.g., oral medication, regional anesthesia, implantable drug delivery systems), surgical (e.g., laminectomy, spinal fusion), or electrical (e.g., spinal cord stimulation, transcutaneous electrical nerve stimulation) manipulation of the pain pathway.
There are several perplexing features of chronic pain that do not fit neatly within the traditional biomedical model, specifically, its suggestion of an isomorphic relationship between pathology and symptoms. For example, pain may be reported even in the absence of an identified pathologic process. It is estimated that one third to one half of all visits to primary care physicians are prompted by symptoms for which no biomedical causes can be detected. In up to 86% of cases, the cause of back pain is unknown despite the performance of sophisticated imaging.
Conversely, significant pathology is noted in up to 35% of asymptomatic people with imaging studies such as computed tomography and magnetic resonance imaging. Yet these individuals do not appear to experience any pain. Thus, some report severe pain with no identifiable pathology, and those with demonstrable pathology may not complain of or even experience any pain.
People differ markedly in how frequently they report physical symptoms, in their propensity to visit physicians when experiencing identical symptoms, and, as noted, in their response to the same treatments. There are large numbers of people with chronic pain problems who do not seek medical attention. For example, in a survey of nurses, Linton and Buer found that the majority reported moderate to severe pain “often or always,” but they indicated that they had not missed a single day of work because of pain. Similarly, Hicks and colleagues observed that almost half of a community-dwelling sample of older people reported considerable back pain, yet the majority did not seek any medical care.
Often the nature of patients’ responses to treatment has little to do with their objective physical condition. For example, White and associates noted that less than a third of people with clinically significant symptoms consult a physician. Conversely, 30% to 50% of patients who seek treatment in primary care do not have specific diagnosable disorders, and in up to 80% of people reporting back pain and the majority of people with chronic headache, no physical basis for the pain can be identified.
There are several potential explanations, not the least of which is the availability of health insurance to cover the costs. As often happens in medicine, when biologic explanations for symptoms are unknown, inadequate, or inconsistent, psychogenic explanations are posed as alternatives.
Psychogenic Model of Chronic Pain
The psychogenic view is the reverse side of the coin of the biomedical model. In this case, if a patient’s report of pain occurs in the absence of objective physical pathology or is disproportionate to the pathology, the pain reports are attributed to a psychological etiology and thus are “psychogenic.” It may be treated as a psychiatric diagnosis within the fourth edition of the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Revised : pain disorder associated with psychological factors or even a pain disorder associated with psychological factors and a general medical condition.
Although the notion of psychogenic pain is ubiquitous, empirical evidence supporting it is scarce. A substantial number of patients with chronic pain do not exhibit significant psychopathology. Moreover, studies suggest that in the majority of cases, the emotional distress observed in these patients occurs in response to the persistence of pain and not as a causal agent and may resolve once the pain is adequately treated.
Psychogenic Model of Chronic Pain
The psychogenic view is the reverse side of the coin of the biomedical model. In this case, if a patient’s report of pain occurs in the absence of objective physical pathology or is disproportionate to the pathology, the pain reports are attributed to a psychological etiology and thus are “psychogenic.” It may be treated as a psychiatric diagnosis within the fourth edition of the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Revised : pain disorder associated with psychological factors or even a pain disorder associated with psychological factors and a general medical condition.
Although the notion of psychogenic pain is ubiquitous, empirical evidence supporting it is scarce. A substantial number of patients with chronic pain do not exhibit significant psychopathology. Moreover, studies suggest that in the majority of cases, the emotional distress observed in these patients occurs in response to the persistence of pain and not as a causal agent and may resolve once the pain is adequately treated.
Secondary-Gain Model of Chronic Pain
The secondary-gain (motivational) model is an alternative to the psychogenic model. From this perspective, reports of pain in the absence of or in excess of the physical pathology are attributed to the desire of the patient to obtain some benefit, such as attention, time off from undesirable activities, or financial compensation— secondary gains . In contrast to the psychogenic model, in the secondary-gain view the assumption is that the patient is consciously attempting to acquire a desirable outcome. Simply put, the complaint of pain in the absence of a pathologic process is regarded as fraudulent.
Behavioral Conceptualizations
Pain is an unavoidable part of human life. No learning is required to activate nociceptive receptors. However, pain is a potent and salient experience. Beyond mere reflexive actions, people must learn to avoid, modify, or cope with noxious stimulation. There are three major principles of behavioral learning that can help us understand the acquisition of adaptive as well as dysfunctional behavior associated with pain.
Classic (Respondent) Conditioning
In his classic experiment, Pavlov discovered that a dog could be taught, or “conditioned,” to salivate at the sound of a bell by pairing the sound with food presented to a hungry dog. Salivation of dogs in response to food is a natural response; however, by preceding the feeding with the sound of a bell, Pavlov’s dogs learned to associate the sound of the bell with imminent feeding. Once this association was learned, or “conditioned,” the dogs were found to salivate at the mere sound of the bell even in the absence of food .
The influence of classic conditioning can be observed in pain patients. Consider physical therapy, a mainstay of treatment for chronic pain patients, where treatment may evoke a conditioned fear response. For example, a patient who experienced increased pain following physical therapy may become conditioned and experience a negative emotional response to the presence of the physical therapist, to the treatment room, and to any contextual cues associated with the nociceptive stimulus. The negative emotional reaction may lead to tensing of muscles, which in turn may exacerbate the pain and thereby further strengthen the association between the presence of the physical therapist and pain.
Once a pain problem persists, fear of motor activities may become increasingly conditioned and result in avoidance of activity in the anticipation of avoidance of pain. Avoidance of pain is a powerful rationale for reduction of activity, where the muscle soreness associated with exercise functions as a justification for further avoidance. Consequently, although it may be useful to reduce movement in the acute stage of pain, limitation of activities can be maintained not only by the pain but also by an anticipatory fear that has been acquired through the mechanism of classic conditioning. Thus, cognitive processes may interact with pure conditioning. It is the anticipation that motivates a conscious decision to avoid specific behavior or stimuli.
With chronic pain, many activities that were initially neutral or even pleasurable may now elicit or exacerbate pain. As a consequence, they are experienced as aversive and actively avoided. Over time, a greater number of stimuli (e.g., activities) may be expected to elicit or exacerbate pain and will be avoided. This process is referred to as stimulus generalization . Thus, the anticipatory fear of pain and restriction of activity—and not just the actual nociception—may contribute to disability. Anticipatory fear can also elicit physiologic reactivity, which may aggravate the pain. As a result, conditioning may directly increase nociceptive stimulation and subsequently the perception of pain.
The conviction by patients that they should remain inactive is difficult to modify as long as avoidance of activity succeeds in preventing aggravation of the pain. By contrast, repeatedly engaging in behavior— exposure —that produces progressively less pain than was predicted (corrective feedback) will be followed by a reduction in anticipatory fear and anxiety associated with the activity. Such transformations add support to the importance of a quota-based physical exercise program, with patients gradually and progressively increasing their activity levels despite fear of injury and discomfort associated with the use of deconditioned muscles. This exposure, in the absence of anticipated pain, provides the corrective feedback that should be positively reinforcing and increase the likelihood of continuing previously avoided activities.
Operant Conditioning—Contingencies of Reinforcement
The effect of environmental factors in shaping the experience of people with pain was acknowledged long ago. However, a new era in thinking about pain began with Fordyce’s extension of operant conditioning to chronic pain. The main focus of operant learning is modifying the frequency of a given behavior—increasing desirable behavior and extinction of maladaptive behavior. The fundamental principle is that if the consequence of a given behavior is rewarding, its occurrence increases, whereas if the consequence is aversive, the likelihood of its occurrence decreases.
When a person is exposed to a stimulus that causes tissue damage, the immediate behavioral response is withdrawal in an attempt to escape from noxious sensations. Such reflexive behavior is adaptive and appropriate. Behavior associated with pain, such as limping and moaning, is called pain behavior . Pain behavior includes overt expressions of pain, distress, and suffering. A critical defining feature of overt behavior is that it is observable and thus has a communicative function. If behavior is observable, it is capable of evoking responses, and it is the consequences following the behavior that are particularly important because they can serve to maintain or diminish the likelihood of the behavior recurring. According to Fordyce, pain behavior can become subjected to the principles of operant conditioning. Such behavior may be positively reinforced directly, such as by attention from a family member, acquaintance, or health care provider. The principles of learning suggest that behavior that is positively reinforced will occur more frequently. Pain behavior may also be maintained by escaping the noxious stimulation with the use of drugs or rest or by avoiding undesirable activities. In addition, well behavior (e.g., activity, working) may not be positively reinforced, and the more rewarding pain behavior may therefore be maintained.
The following example illustrates the role of operant conditioning. When back pain flares up, the individual may lie down and hold her back. Her husband may observe her behavior and respond by offering to rub her back. This response may positively reward the woman, and her pain behavior (i.e., lying down) may be repeated even in the absence of severe pain. In other words, her pain behavior is being maintained by the learned consequences. The woman’s pain behavior may be negatively reinforced if she is permitted to avoid undesirable activities. For example, her husband may suggest that they cancel their evening plans with his brother, an activity that she preferred to avoid in the past. In this situation, her husband provided extra attention, comfort, and the opportunity to avoid an undesirable social obligation.
Table 12.1 presents examples of basic operant principles in chronic pain. The operant learning paradigm does not explain the etiology of pain or initiation of the behavior but rather focuses primarily on maintenance of pain behavior and deficiency of well behavior. Adjustment of reinforcement principles will likely modify the probability of recurrence of pain behavior and well behavior.
| Principle | Consequence | Probability of the Behavior Recurring |
|---|---|---|
| Positive reinforcement | Reward the behavior | More likely |
| Negative reinforcement | Prevent or withdraw aversive results | More likely |
| Punishment | Punish the behavior | Less likely |
| Neglect | Prevent or withdraw positive results | Less likely |
It is important to not make the mistake of viewing pain behavior as being synonymous with malingering . Malingering involves the patient consciously and purposely faking a symptom such as pain for some gain, usually financial (secondary gain). In the case of pain behavior, there is no suggestion of conscious deception but rather the unintended performance of pain behavior resulting from environmental reinforcement contingencies. Contrary to the beliefs of many third-party payers, there is little support for the contention that outright faking of pain for financial gain is prevalent.
Social-Learning Processes
From the social-learning perspective, pain behavior may be acquired through observational learning and modeling processes. That is, people can acquire behavioral responses that were not previously in their repertoire by the observation of others, particularly those whom they view as similar to themselves.
Children develop attitudes about health and health care and the perception and interpretation of symptoms and physiologic processes from their parents and the social environment. They learn appropriate and inappropriate responses to injury and disease and thus may be more or less likely to ignore or over-respond to the symptoms that they experience as a result of behavior modeled in childhood. The culturally acquired perception and interpretation of symptoms determine how people deal with disease states. The observation of others in pain is an event that captivates attention. Such attention may have survival value, may help avoid experiencing more pain, and may help learn what to do about acute pain.
From the earliest years, infants, toddlers, and young children are exposed to numerous painful episodes from bumps and falls. Thus they have plenty of opportunity to observe the reactions that they receive. Children of parents with chronic pain may make more pain-related responses during stressful times than would children with healthy parents. These children tend to exhibit greater illness behavior (e.g., complaints, days absent from school, visits to the school nurse) than do children of healthy parents. Models can influence the expression, localization, and methods of coping with pain. Physiologic responses may even be conditioned during observation of others in pain. Expectancies and actual behavioral responses to nociceptive stimulation are based, at least partially, on prior experience either directly or from the observation of others. This may contribute to the marked variability in response to objectively similar degrees of physical pathology observed.
The biomedical, psychogenic, secondary-gain, and behavioral views are unidimensional. Reports of pain are ascribed to either physical or psychological factors. Rather than being categorical, either somatogenic or psychogenic, both physical and psychological components may interact to create and influence the perception and experience of pain.
Any physical abnormalities that are identified may be moderated by coexisting psychosocial influences. The complexity of pain is especially evident when it persists over time, during which a range of psychological, social, and economic factors interact with the physical pathology to modulate patients’ reports of pain and the impact of pain on their lives. In the case of chronic pain, health care providers need to not only search for the physical source of the pain through examination and diagnostic tests but also examine the patient’s mood, fears, expectancies, coping efforts, and resources; the responses of significant others; and the impact of pain on the patient’s life.
Persons experiencing pain, particularly chronic pain, have a continuing quest for relief that remains elusive, which can lead to feelings of frustration, demoralization, and depression, thus compromising the quality of all aspects of their lives. People with chronic pain are confronted with not only the stress of pain but also a cascade of ongoing problems (e.g., financial, interpersonal). Moreover, the experience of “medical limbo” (i.e., the presence of a painful condition that eludes diagnosis and carries the implication of either psychiatric causation or malingering on the one hand or an undiagnosed potentially disabling condition on the other) is itself a source of significant stress and can result in psychological distress.
Biomedical factors, in the majority of cases, appear to instigate the initial report of pain. Over time, however, psychosocial and behavioral factors may serve to maintain and exacerbate the level of pain, influence adjustment, and contribute to excessive disability. Following from this view, pain that persists over time should not be viewed as being solely physical or solely psychological; the experience of pain is maintained by an interdependent set of biomedical, psychosocial, and behavioral factors.
People with chronic pain frequently terminate active efforts to manage the pain and instead turn to passive coping strategies, such as inactivity, medication, or alcohol, to reduce the pain and emotional distress. They also absolve themselves of personal responsibility for managing their pain and as a substitute rely on family and health care providers. The thinking of chronic pain patients has been shown to contribute to the exacerbation, attenuation, and maintenance of pain, pain behavior, affective distress, adjustment to chronic pain, health care seeking, response to treatment, and disability.
The important role of the behavioral and environmental contingencies of reinforcement in chronic pain has already been described. However, another set of psychological factors—affective and cognitive factors—play equally important roles.
Affective Factors
Pain is ultimately a subjective, private experience, but it is invariably described in terms of sensory and affective properties. As defined by the International Association for the Study of Pain, “[Pain] is unquestionably a sensation in a part or parts of the body but it is also always unpleasant and therefore also an emotional experience.” The central and interactive roles of sensory information and the affective state are supported by an overwhelming amount of evidence. The affective components of pain include many different emotions, but they are primarily negative emotions. Depression and anxiety have received the greatest amount of attention in chronic pain patients; however, anger has recently attracted considerable interest as an important emotion in chronic pain patients.
In addition to affect being one of the three interconnected components of pain, pain and emotions interact in a number of ways. Emotional distress may predispose people to experience pain, be a precipitant of symptoms, be a modulating factor that amplifies or inhibits the perception of pain severity, be a consequence of persistent pain, or be a perpetuating factor. Moreover, these potential roles are not mutually exclusive, and any number of them may be involved in a particular circumstance and interact with cognitive appraisal. For example, the literature is replete with studies demonstrating that the current mood state modulates reports of pain, as well as tolerance of acute pain. Levels of anxiety have been shown to influence not only the severity of pain but also complications following surgery and the number of days of hospitalization required. The level of depression has been observed to be closely tied to chronic pain.
Although we provide an overview of research on the predominant emotions—anxiety, depression, and anger—associated with pain individually, it is important to acknowledge that these emotions are not as distinct when it comes to the experience of pain. They interact and augment each other over time.
Anxiety
It is common for patients with symptoms of pain to be anxious and worried, especially when the symptoms are unexplained, as is often the case with chronic pain syndromes. For example, in a large-scale, multicenter study of patients with fibromyalgia syndrome, between 44% and 51% acknowledged that they were anxious. People with persistent pain may be anxious about the meaning of their symptoms and their future—will their pain increase, will their physical capacity diminish, or will their symptoms result in progressive disability wherein they ultimately need a wheelchair or are bedridden? In addition to these sources of fear, those with persistent pain may be worried that, on the one hand, people will not believe that they are suffering and, on the other, they may be told that they are beyond help and will “just have to learn to live with it.” Fear and anxiety also relate to activities that people with pain anticipate will increase their pain or exacerbate whatever physical factors might be contributing to the pain. These fears may contribute to avoidance and motivate inactivity and, ultimately, greater disability. Continual vigilance and monitoring for noxious stimulation and the belief that it signifies progression of disease may render even low-intensity aversive sensations less bearable. In addition, such fears will contribute to increased muscle tension and physiologic arousal, which may exacerbate and maintain the pain.
The threat of intense pain captures attention in such a way that individuals have difficulty disengaging from it. The experience of pain may initiate a set of extremely negative thoughts, as noted previously, and arouse fear—fear of inciting more pain and injury or fear of their future impact. Fear and anticipation of pain are cognitive-perceptual processes that are not driven exclusively by the actual sensory experience of pain and can exert a significant impact on the level of function and pain tolerance. People are motivated to avoid and escape from unpleasant consequences; they learn that avoidance of situations and activities in which they have experienced acute episodes of pain will reduce the likelihood of re-experiencing pain or causing further physical damage. They may become hypervigilant to their environment as a way of preventing the occurrence of pain.
Investigators have suggested that fear of pain, driven by the anticipation of pain and not by the sensory experience of pain itself, produces strong negative reinforcement for the persistence of avoidance behavior and the putative functional disability in pain patients. Avoidance behavior is reinforced in the short term through a reduction of the suffering associated with noxious stimulation. Avoidance, however, can be a maladaptive response if it persists and leads to increased fear, limited activity, and other physical and psychological consequences that contribute to disability and persistence of the pain.
Studies have demonstrated that fear of movement and fear of injury or reinjury are better predictors of functional limitation than biomedical parameters or even the severity and duration of the pain are. For example, Crombez and colleagues showed that pain-related fear was the best predictor of behavioral performance in trunk extension, flexion, and weight-lifting tasks, even after the effects of pain intensity are statistically controlled. Moreover, Vlaeyen and associates found that fear of movement and injury or reinjury was the best predictor of self-reported disability in chronic back pain patients and that the physiologic sensory perception of pain and biomedical findings did not add any predictive value. The importance of fear of activity appears to generalize to daily activities, as well as the to clinical experimental context. Approximately two thirds of people with chronic low back pain avoid back-straining activities because of fear of injury. For example, fear avoidance beliefs about the physical demands of a job are strongly related to disability and work lost during the previous year, even more so than the severity of pain or other pain variables. Interestingly, a reduction in pain-related anxiety predicts improvement in functioning, affective distress, pain, and pain-related interference with activity. Clearly, fear, pain-related anxiety, and concerns about avoidance of harm all play important roles in chronic pain and need to be assessed and addressed during treatment.
Pain-related fear and concerns about avoidance of harm both appear to exacerbate symptoms. Anxiety is an affective state that is greatly influenced by appraisal processes; to cite the stoic philosopher Epictetus, “There is nothing either bad or good but thinking makes it so.” Thus, there is a reciprocal relationship between the affective state and cognitive-interpretive processes. Thinking affects mood, and mood influences appraisals and, ultimately, the experience of pain.
Depression
Clinical data suggest that 40% to 50% of chronic pain patients experience significant depression. Epidemiologic studies provide abundant evidence confirming a strong association between chronic pain and depression but do not address whether chronic pain causes depression or depression causes chronic pain. Prospective studies of patients with chronic musculoskeletal pain have suggested that chronic pain can cause depression, that depression can cause chronic pain, and that they exist in a mutually reinforcing relationship.
One fact often raised to support the idea that pain causes depression is that the current depressive episode often began after onset of the pain problem. The majority of studies appear to support this contention. However, several studies have documented that many patients with chronic pain, especially disabled patients seen in pain clinics, have often had previous episodes of depression that predated their pain problem by years. It is important to acknowledge that studies based on patients treated at pain treatment facilities may be biased in that patients treated at these facilities have been shown to have exceedingly high levels of depression, which may have prompted referral, and they may not be representative of all individuals with persistent pain. One important prospective study demonstrated that levels of depression predicted the development of low back pain 3 years following the initial assessment. Patients with depression were 2.3 times more likely to report back pain than were those who did not report depression. Depression was a much stronger predictor of incident back pain than any clinical or anatomic risk factors. This has led some investigators to propose that there may exist a common trait of susceptibility to dysphoric physical symptoms (including pain) and to negative psychological symptoms (including anxiety and depression). They concluded that “pain and psychological illness should be viewed as having reciprocal psychological and behavioral effects involving both processes of illness expression and adaptation.” Once chronic pain has been diagnosed, it no longer matters which is the cause and which is the consequence—pain or depression. Both need to be treated.
It is not surprising that a large number of chronic pain patients are depressed. It is interesting to ponder the converse. Given the nature of the symptom and the problems created by chronic pain, why is it that all such patients are not depressed? Turk and colleagues examined this question and determined that patients’ appraisal of the effects of the pain on their lives and their ability to exert any control over the pain and their lives mediated the link between pain and depression. That is, patients who believed that they could continue to function despite their pain and who believed that they could maintain control despite their pain did not become depressed.
Anger
Anger has been widely observed in people with chronic pain. Pilowsky and Spence reported “bottled-up anger” in 53% of chronic pain patients. Kerns and coworkers noted that internalization of angry feelings was strongly related to measures of pain intensity, perceived interference, and the reported frequency of pain behavior. Summers and colleagues examined patients with spinal cord injuries and found that anger and hostility were powerful predictors of pain severity. Moreover, even though chronic pain patients in psychotherapy might present an image of themselves as being even tempered, 88% of the patients treated acknowledged their feelings of anger when explicitly sought.
Frustrations related to the persistence of symptoms, limited information on etiology, and repeated treatment failures, along with anger toward employers, insurers, the health care system, family members, and themselves, all contribute to the general dysphoric mood of these patients. The effects of anger and frustration on exacerbation of pain and acceptance of treatment have not received much attention, but it would be reasonable to expect that the presence of anger may serve as a complicating factor that increases autonomic arousal and blocks motivation and acceptance of treatments oriented toward rehabilitation and management of the disability rather than cure, which are often the only treatments available for chronic pain.
When a person with pain is angry, there are a range of possible targets (e.g., employer, insurance company, health care providers). Fernandez and Turk proposed that the specificity of targets toward which patients direct angry feelings may be important in understanding the relationship between pain and anger. There may be some targets of anger that are more relevant to the chronic pain experience than others.
Okifuji and colleagues found that 60% of patients expressed anger toward health care providers, 39% toward significant others, 30% toward insurance companies, 26% toward employers, and 20% toward attorneys. The target of anger most commonly acknowledged, however, was oneself (endorsed by approximately 70% of the sample). Overall, correlations between anger and pain severity have been shown to be statistically significant and range from .17 to .35. Okifuji and coauthors reported that anger was significantly correlated with pain intensity ( r = .30 to .35). They also reported that anger was significantly correlated with disability ( r = .26) and was highly associated with depression ( r = .52).
The precise mechanisms by which anger and frustration exacerbate pain are not known. One reasonable possibility is that anger exacerbates pain by increasing physiologic arousal. For example, Burns and coauthors reported the results of a study in which it was demonstrated that anger-induced stress produces increased muscle tension, which in turn predicts greater severity of pain in chronic back pain patients. It was found that this effect was specific to anger; a measure of depression that was significantly correlated with pain was not associated with increased muscle reactivity.
A negative mood in chronic pain patients is likely to affect treatment motivation and adherence to treatment recommendations. For example, patients who are anxious may fear engaging in what they perceive as demanding activities, patients who are depressed and feel helpless may have little initiative to comply, and patients who are angry with the health care system are not likely to be motivated to respond to recommendations from yet another health care professional.
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