Chronic Pain Research Paper

It is important to distinguish pain from nociception. Nociception is a physiological process by which transduction of sensory information is activated in specialized nerve endings that convey information about tissue damage (e.g., location, descriptive features) to the central nervous system. Pain, on the other hand, is an integrated perceptual process. The International Association for the Study of Pain (IASP) recognizes the complexity of pain and treats it as a phenomenological experience unique to each person. According to the IASP definition, pain is ‘an unpleasant sensory and emotional experience normally associated with tissue damage or described in terms of such damage’ (Merskey 1986). In addition to this global definition, many commonly used pain terms and related phenomena have been described (Turk and Okifuji 2001). For example, pain may be acute and a response to an identifiable trauma or disease, or it may be episodic and occur intermittently as in the case of migraine headache. Pain may also be relatively constant, extending for years. Unlike those with acute or recurrent pain, people with chronic pain may suffer 24 hours a day, 365 days a year. Table 1 includes a list of four classes of pain based upon timing and clinical implications.

In this research paper an overview is provided of the current understanding of pain and its management. First the conceptualizations that have dominated views of pain historically are reviewed. The current conceptualizations that integrate multifactorial aspects of pain are described. The paper also focuses on psychosocial factors that have been shown to contribute to the subjective experience of pain as well as adaptation and response to treatment. Following the discussion of model of pain, a historical overview of the most common perspectives and treatments of pain is presented. The importance of a multidisciplinary approach to understanding and treating complex chronic pain syndromes is stressed. Finally, the psychosocial strategies that incorporate behavioral and cognitive– behavioral perspectives with the goals of improving pain and functioning of people suffering from pain are emphasized. It is not meant to be suggested, however, that pain is purely psychological or that physical factors are unimportant. Rather emphasis is put on psychosocial factors, as they have previously been less integrated into conventional thinking about chronic pain. The psychological approaches described are almost always employed within the multidisciplinary treatment program (Flor et al. 1992).

2. Historical Conceptualizations Of Pain

Over the centuries, many prominent scholars have attempted to uncover the mechanisms underlying pain. Perhaps among the most influential was the seventeenth century French philosopher, Rene Descartes. Descartes conceptualized pain as the result of representation of a painful stimulus traveling along the nervous system starting at the periphery (the flame depicted in Figure 1 that will travel along the nerve from the periphery to the spinal cord eventually reaching the brain where it acknowledged as ‘pain’). Descartes’s approach formed the basis for the mind– body dualism that plays a prominent role in the understanding and treatment of pain.

2.1 Biomedical ( Pain = Physical Pathology) Model

The traditional biomedical view that continues to dominate is reductionistic. This perspective assumes that every report of pain must be associated with a specific physical cause (e.g., pain caused by the flame in Figure 1). As a consequence, the extent of pain reported should be directly proportional to the amount of tissue damage. The expectation is that once the physical cause has been identified, appropriate treatment will follow and positive outcomes will be attained. Treatment typically focuses on removing the putative cause of the pain, or by chemically or surgically disrupting the pain pathways (cutting or blocking the transmission of signals from the periphery to the brain). According to this model, once the cause of the pain is removed or the pain pathways are blocked, pain should be eliminated.

There are, however, several perplexing features of pain that do not fit neatly into the biomedical model with its suggestion of a one-to-one relationship between tissue pathology and symptoms. Most notably, not all pain accompanies observable pathology. For example, in over 85 percent of the cases of back pain, one of the most common pain conditions in Western countries, the cause of the pain is unknown (Deyo 1986). Conversely, physical pathology does not necessarily cause pain. Diagnostic imaging studies identify significant pathology in up to 35 percent of people who are pain-free (Jensen et al. 1994). Thus, a paradox exists. On one hand there are people without significant pathology who report severe pain and on the other hand there are people with objectively determined physical pathology who do not report the presence of any pain.

2.2 Psychogenic (‘It’s All In Your Head’) Model

According to this model, pain, in the absence of physical pathology, is a result of the patient’s inherent personality traits or psychological problems. The psychogenic view is posed as the flip side of the coin from the physical or biomedical model. From this perspective, if the report of pain occurs in the absence of, or is disproportionate to, objective physical pathology, then, ipso facto, the pain reports must have a psychological etiology. Thus, a dichotomy is posed, pain is either somatagenic or psychogenic.

2.3 Motivational (Secondary Gain) Model

A related conceptualization to the psychogenic one described specifically focuses upon motivation. From this perspective, reports of pain in the absence of physical pathology are attributed to the desire of the person complaining to obtain some benefit such as attention, time off from undesirable activities, or financial (disability) compensation (i.e., secondary gain). Unlike the psychogenic model, in the motivational model, the assumption is that the person is consciously attempting to acquire a desirable outcome based on the complaint of pain. Thus, the complaint of pain in the absence of pathology is taken to be fraudulent. Simply put, the person who reports pain in the absence of objective pathology is lying in order to obtain a desired outcome.

2.4 Operant (Social Reinforcement) Model

The operant or social reinforcement model is based upon the behavioral learning paradigm in which the probability of exhibiting a specific behavior depends on the consequences that follow the behavior. Behaviors are most likely to recur when they are reinforced by desirable consequences (e.g., attention, sympathy), by removal of something aversive (e.g., participating in undesirable tasks, work activity), or avoidance of some undesirable consequence. Fordyce (1976) suggested that certain behaviors associated with pain (e.g., limping, grimacing) could be reinforced to the point where the behaviors recur without the original nociceptive stimuli. Pain behaviors that are consistent with acute pain and that may be reflexive responses to noxious stimulation, may become chronic pain behaviors even when there is no physiological basis for exhibiting those behaviors. Thus, in this model, chronic pain is considered a manifestation of learned behaviors that need to be extinguished, whereas well behaviors, such as activity, need to be increased. The laws of operant learning are viewed as playing a central role in the maintenance of chronic pain behaviors. The role of other factors, such as physiology, emotions, the persons’ attitudes and beliefs, play very little role in the operant model.

3. Multidimensional Conceptualization Of Pain

The unidimensional models described fail to explain individual and situational variation in pain experiences. The paper will now focus on more contemporary models of pain with multifactorial bases.

3.1 Gate Control Theory

Melzack and Wall (1965) developed the gate control theory that integrated physical and psychological factors regarding pain experience. Briefly, the gate control theory proposes that a mechanism in the dorsal horn of the spinal cord acts as a ‘gate’ that can inhibit or facilitate transmission of nerve impulses from the periphery to the brain. Melzack and Wall postulated that not only injury sites at the periphery influence the gating mechanism but also by people’s psychological states. They suggested that the reticular formation in the brain functions as a central biasing mechanism inhibiting the transmission of pain signals. Psychological factors that affect the reticular formation may modulate the pain experience.

Melzack and Wall emphasized the modulation of inputs in the dorsal horn of the spinal cord and on the dynamic role of the brain in pain processes and perception. As a result, the gate control theory integrates psychological variables such as past experience, attention, and other cognitive activities into current research on and therapy for pain. Prior to this formulation, psychological processes largely were dismissed as merely reactions to pain. This new model suggested that severing nerves, the putative pain pathways, was inadequate as a host of other factors modulated the input. Perhaps the major contribution of the gate control theory was that it highlighted the central nervous system as playing an essential role in the perception and interpretation of nociceptive stimuli associated with the experience of pain.

The physiological details of the gate control model have been challenged and it has been suggested that the model is incomplete. As additional knowledge has been gathered since the original formulation of the gate control model, specific points have been disputed and physiological details of the model have been refined. The conceptual aspects of the gate control theory have, however, proved remarkably resilient and flexible in the face of accumulating scientific evidence. The gate control model still provides a powerful summary of the phenomena observed in the spinal cord and brain, and has the capacity to explain many of the most puzzling problems encountered in the clinic. The gate control theory has had enormous heuristic value in stimulating further research in the basic science of pain mechanisms and in spurring new approaches to treatment.

3.2 Cognitive–Behavioral Model

The focus of the cognitive–behavioral model is on the person’s own subjective perspectives (e.g., attitudes, believes, expectations) and feelings about their plight (Turk et al. 1983). The model assumes that although nociceptive stimuli precede pain, how the person perceives the nociceptive event forms a total pain experience by interacting with the sensory event. For example, negative and pessimistic views by people about their pain condition (e.g., ‘It’s hopeless and it will never get better.’) and their capabilities for managing pain and stress (e.g., ‘There is absolutely nothing I can do about my pain.’) are likely to exacerbate their emotional distress and sense of disability. Similarly, if one views pain as inevitable (e.g., ‘I was injured, that is why I hurt.’), attention to sensory events may become pronounced, and as a consequence, relatively subtle sensory information may be interpreted as being painful.

The cognitive–behavioral model also acknowledges the effects of physiological factors and the environment on behaviors and of behaviors on thoughts and feelings. Reporting of symptoms to family and health care providers is influenced by how people view their pain problem and, of course, physical pathology.

The basic assumption of the cognitive–behavioral model is that people are not passive entities who simply react reflexively to nociception or social reinforcement, but actively engaging themselves in defining the experience. Based upon past learning and medical history, people develop subjective representations of illness and symptoms—‘schemas.’ These schema becomes the filters through which people process new sensory stimulus (Cioffi 1991).

Beliefs about the meaning of pain and one’s ability to function despite pain are important aspects of pain schema. When confronted with pain, people draw causal, covariational, and consequential inferences about their symptoms based upon their own schematic references. For example, if the schema includes a strong belief that all physical activities must be ceased when experiencing pain and that pain is an acceptable justification for neglecting domestic and occupational responsibilities, poor adaptation and coping are likely to result (Williams and Thorn 1989).

4. Treatments

As has been discussed previously, pain is a complex phenomenon and diverse in its nature and degrees of associated impairment. It is therefore important to know the objectives of treatments for pain. Many pain states are expected to remit over time with little intervention required. Some types of acute pain may require surgical or pharmacological therapy to treat underlying pathology or to block noxious sensory information. A more comprehensive plan is required for treating people with chronic pain. Many people with chronic pain live with their pain for years, and the adverse effects of pain may be generalized across all aspects of their lives, familial, social, occupational, as well as physical. Given the multilayered problems associated with pain, treatment goals become more global. Rather than treating pain, it becomes necessary to treat people with chronic pain.

4.1 Historical Approaches To Treatment

The earliest approach to treating pain was aligned closely with unimodal views; particularly those based on the biomedical model. Pain was thought of as reflecting a physical problem. Early treatment approaches focused on the idea that something had to be removed or signals had to be interrupted to bring about relief from pain. The earliest reference to medication is referred to in an ancient Egyptian text dating back to 1550 BC where the god Isis recommended the use of opium to relieve Ra’s headache (Bonica 1953). Ancient pain treatments have included crocodile dung, oils derived from ants, earthworms and spiders, spermatic fluid from frogs, and moss scraped from the skull of a victim of a violent death. A quick surf of the Internet will reveal that many equally esoteric preparations are endorsed readily even today.

The most common contemporary treatment approaches continue to be based primarily on the biomedical model of pain involving pharmacotherapy (with new drugs touted on an almost weekly basis) or surgery performed along nearly every site of the nervous system including the periphery (sympathectomy), the spinal cord (percutaneous cordotomy, destructive neural blockade), and the brain (thalamatomy, prefrontal lobotomy). Although current methods are more sophisticated than the ancient ones, the basic principles remain the same—alteration of an alleged physical cause should result in symptomatic improvement. Some modalities are quite helpful and a great many people suffering from acute and cancer pain have benefited from those advances in pain medicine and surgery. However, surgery and pharmacotherapy are not panaceas and do not result in adequate control of pain in all cases.

In contrast, some primitive treatment methods focused on the cause of pain being purely psychogenic. The assumption was that if no physical cause could be detected then the pain must be caused by emotional disturbance that required treatment and once psychological problems were resolved the pain would resolve. Such a psychogenic bias can be seen in the current Diagnostic and Statistical Manual (American Psychiatric Association 1994) for mental disorder. Two types of pain disorders are listed as mental disorders: Pain Disorder Associated with Psychological Factors and Pain Disorder Associated with Both Psychological Factors and a general medical condition. In both cases, pain is the primary complaint, with psychological factors being considered important in the onset, severity, exacerbation, or maintenance of the pain. A somewhat presumptuous assumption underlying these disorders is that the ‘appropriate’ physical etiology of chronic pain must be identifiable (e.g., free from psychological factor) or patients are suffering from a psychiatric disorder. The assumption ignores the current consensus that pain is not a pure sensory experience but is inherently a biopsychosocial phenomenon resulting in an intense, subjective experience of discomfort.

4.2 Comprehensive Approaches To The Treatment Of The Person With Chronic Pain

The recognition of pain, particularly chronic pain, as a major healthcare issue, has resulted in the development of growing number of specialists and specialized facilities offering treatments for pain over the last few decades. In the United States alone, over 3300 pain specialists and treatment facilities have been identified (Marketdata Enterprises 1995).

Comprehensive, multidisciplinary treatments involving teams of professionals (physicians, psychologists, physical therapists, occupational therapists, vocational therapists, and nurses) have been developed to treatment patients with the most recalcitrant problems. Flor et al. (1992) summarized the major characteristics of these patients as those with seven years of pain history and at least one failed surgery. These patients are likely to be unemployed, receiving disability payments, and present an array of psychosocial and motivational issues. In addition to the suffering associated with chronic pain, these patients present socioeconomic difficulties for society due to loss of productivity and costs associated with disability payments and medical care.

Focus will be on the pain management approaches that have been developed based upon the psychological models described earlier. Although these interventions can be used separately, with few exceptions (e.g., biofeedback for tension-type headache) unimodal approaches are less effective than comprehensive rehabilitation programs. Typically, the psychological approaches are part of more comprehensive rehabilitation program in which psychologists work together with therapist from other disciplines (e.g., physicians and physical therapists).

The multidisciplinary rehabilitation programs are philosophically distinct from unimodal medical and surgical treatments. The first and most critical distinction is that the major goals of the multidisciplinary treatment programs extend beyond pain relief. Rather, they focus on physical and psychological functioning, as well.

Overall, rehabilitation programs that incorporate a significant psychosocial component are most effective in improving patient functioning, returning patients to work, reducing use of analgesics, reducing health care utilization, and reducing disability costs (Okifuji et al. 1998). ‘Cure’ of pain (e.g., total relief from pain) is, unfortunately, rarely attained. Reduction of pain is usually only moderate but comparable to that observed with usual medical and surgical approaches that are more invasive and have increased likelihood of iatrogenic consequences.

4.2.1 Treatment Based On The Operant Model. As noted previously, the operant model of pain focuses upon pain-related behaviors believed to be maintained by social reinforcement. Such behaviors are considered to be maladaptive and thus need to be eliminated. As discussed, reinforcers are the consequences of behaviors that increase the likelihood that behaviors will be repeated. Thus, treatment involves eliminating the rewarding consequences of pain behaviors and increasing the positive responses for activity and other well behaviors. In these programs, moaning, grimacing, and other pain behaviors are ignored. Usual activities of daily living and functional exercises are prescribed and positively reinforced. Medications are made time-contingent, rather than prescribed on an ‘as needed’ (prn) basis that is believed to reinforce positively the pain behaviors. Simultaneous with the attempts to extinguish pain behaviors, operant treatments are designed to help patients acquire a set of new, more adaptive, behaviors. Quota-based exercise programs with gradually increasing functional activities form the core of operant treatment.

Although operant factors may play an important role in the maintenance of disability, the model has been criticized at two levels. First, it fails to integrate factors other than reinforcement, such as sensory, emotional, and cognitive factors in the overall pain experience. Second, the assumption that pain behaviors are acquired, maintained, and extinguished solely through environmental reinforcement contingencies is questioned. For example, physical signs, patients’ self-efficacy beliefs, and depression are also reportedly related to pain behaviors (Buckelew et al. 1953).

Pain behaviors have been considered to be maladaptive manifestations of pain, guided by an incentive for attention or avoidance of physical activity. However, pain behaviors may be functional if indeed the behaviors protect patients from further injury or exacerbation of pain. Determination of whether an overt pain behavior in a given patient is functional or maladaptive needs to be based upon careful assessment of various factors associated with his or her pain conditions not just the reinforcement contingencies. Despite the criticisms, operant-based treatments generally are successful in reducing overt pain behaviors, increasing well-behaviors, and decreasing analgesic medication.

4.2.2 Treatments Based On The Cognitive–Behavioral Model. As noted earlier, the cognitive–behavioral model of pain acknowledges the importance of cognitive variables interacting with sensory, affective, behavioral ones to establish, maintain, and exacerbate the pain experience. The nature of specific techniques may vary from program to program, however, the primary goals of the cognitive–behavioral approach are relatively uniform (i.e., enhancement of patients’ sense of control over their symptoms, increased use of adaptive skills to cope with pain and stress). Cognitive–behavioral therapy is designed to assist patients to identify, evaluate, and correct maladaptive conceptualizations and dysfunctional beliefs about themselves and their predicament. Additionally, patients are taught to recognize the connections linking cognition, affect, and behavior along with their joint consequences. Patients are encouraged to become aware of and to monitor the impact those maladaptive thoughts may have in the maintenance and exacerbation of maladaptive behaviors (see Table 2 for common maladaptive thoughts).

The cognitive–behavioral approach consists of four interrelated phases. These include (a) reconceptualization, (b) acquisition of coping skills and self-management strategies, (c) skill consolidation, and (d) generalization and maintenance. The first phase, reconceptualization, uses cognitive restructuring, a method that encourages people to identify and change maladaptive thoughts and feelings that are associated with the experience of pain. The crucial element in successful treatment is bringing about a shift in the patient’s thought processes, away from well-established, habitual, and automatic but maladaptive thoughts toward more hopeful and rational ones. Cognitive restructuring helps foster the reconceptualization by helping patients to become aware of the role thoughts and emotions play in potentiating and maintaining stress and pain. The aim of this phase is to combat the sense of demoralization that many with chronic pain experience. Generally, the process of cognitive restructuring begins with a presentation of a situation or event that provoked a pain-related response. The situation is dissected to identify key thoughts and feelings that precede, accompany, and follow an episode or exacerbation of ongoing pain and pain-related problems. Then patients are encouraged to challenge the legitimacy of the thoughts—was it true? Was it reasonable? Was it the only way to respond? What alternatives are available? and so on. Patients are instructed to gather evidence for or against their own maladaptive automatic thoughts. Alternatives are discussed, with the suggestion that different ways of thinking can affect mood, behavior (e.g., reducing physical activity leading to greater disability) and even physiological activity (e.g., increase muscle tension and thereby exacerbating pain).

The second phase is the acquisition of self-management skills. A wide variety of techniques have been shown to be effective for reducing suffering and disability. Some of these strategies are self-regulatory skills (e.g., relaxation, controlled breathing, and attention diversion) that allow pain sufferers to regulate their own physiological responses that may be involved in the maintenance and exacerbation of pain. Other self-management strategies include stress-reduction skills (e.g., problem-solving, behavioral rehearsals) that allow people with chronic pain to effectively manage the stress-inducing thoughts, behaviors, and emotions that trigger pain, emotional distress, and other maladaptive responses. Instead of being a passive recipient of a medical intervention (e.g., medication, anesthetic nerve block), patients now learn to use self-management strategies to play an active role in managing the myriad of problems created by the presence of persistent pain. Research has suggested that there is no one specific coping skill that best manages pain and disability (Fernandez and Turk 1992). It is recommended generally that chronic pain patients should be taught various types of coping skills to help them acquire a range of options.

Phase 3 is skill consolidation. During the skill-consolidation phase, patients practice and rehearse the skills that they have learned during the acquisition phase and apply them outside the hospital or clinic. Practice may start with the mental rehearsal, during which patients imagine using the skills in different situations. Therapists can make use of role-playing, in which patients rehearse learned skills in situations that mirror their home environments. Therapists may start with a relatively easy examples and then introduce scenarios that are progressively more realistic. The importance of skill consolidation through homepractice cannot be overstated. When patients practice skills at home, it is useful for them to record their experiences including any difficulties that arise. Once problems associated with using the newly acquired skills are identified, these become targets for further discussion.

The final stage is phase 4; the preparation for generalization and maintenance. To maximize the likelihood of maintenance and generalization of treatment gains, therapists focus upon the cognitive activity of patients as they confront problems throughout treatment (e.g., failure to achieve goals, plateaus in progress, recurrent stress). These circumstances are used as opportunities to assist patients to learn how to handle setbacks and lapses because they are probably inevitable parts of life and will occur after the termination of the treatment. In the final phase of treatment, discussion focuses on ways of predicting and dealing with symptoms and related problems following treatment termination. Patients are encouraged to anticipate future problems, stress, and symptom-exacerbating events during treatment and to plan how to respond and cope with these problems.

Since self-initiating pain management is a key factor in pain rehabilitation. Some type of cognitive– behavioral approach generally is included in a multidisciplinary pain program.

Cognitive–behavioral approaches have been demonstrated to be effective with a wide range of debilitating pain syndromes including low back pain (Lanes et al. 1995), arthritis (Parker et al. 1995), and fibromyalgia (Turk et al. 1998). Moreover, these methods have been shown to be effective with children (Walco et al. 1992) and geriatric samples (Calfas et al. 1992).

5. Summary

This research paper reviewed the definition of pain and the historical context within which pain has been conceptualized, made a distinction between nociception (a sensory process) and pain (a perception), and described the most common conceptualizations based the unidimensional and multidimensional models of pain. It was noted that treatment strategies have closely followed the conceptualizations of pain and have included unidimensional modalities (i.e. biomedical, psychogenic) and progressed to multidimensional modalities.

Although pain generally is considered a physical phenomenon, pain involves various cognitive, affective, and behavioral features. These psychological factors are important not only in determining the perception of pain, but also defining disability and patients’ general well-being. It should be clear from the review that pain has three main components: physical, psychosocial, and behavioral, that interact to define the unique pain experience. Because the pain experience is subjective and idiosyncratic, it cannot be understood without evaluating how patients perceive and appraise their conditions. A complete clinical picture involves consideration of how patients view their plight. By understanding the phenomenology of chronic pain and disability, effective treatment can be planned to alleviate persistent and debilitating pain, improve physical and psychological functioning, thereby reducing the disability that accompanies chronic pain.

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