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Pain is certainly one of the most common reasons for which patients seek medical treatment. The relief of pain is one of the physicians primary tasks, and the expectation of this relief often leads to the patient's idealization of the physician. While current understanding of the scientific basis of acute pain is minimal, that of chronic pain is even less. Chronic pain appears to serve no biological function, yet it remains resistant to treatment. Moreover, this condition seems to inhibit the patient's capacity to function and to enjoy life instead of serving the patient in some protective function. The patient gradually gives in to changes in behavior and affect, which in themselves are undesirable and maladaptive and, in turn, require treatment. Finally, besides the physical and emotional turmoil, chronic pain adds significant economic as well as social stress to the patient, family and society (Kouyanou, Pither, Rabe-Hesketh, & Wessely, 1998).

The present paper will present an overview of the latest advances in the literature related to non-pathological or benign-chronic pain. In other words, for purposes of this paper, chronic pain will refer to pain of a chronic nature for which no organic or tissu pathology is presently identified, eventhough the origins of that pain might have been of organic nature. The first section will present a biopsychosocial definition of chronic pain and will contrast chronic with acute pain. The second section will discuss the different methods that serve the assessment process of chronic pain. The third section will review the latest epidemiological data of chronic pain and will emphasize preventive care methods (primary, secondary and tertiary). The fourth section will present the role of treatment (biopsychosocial approaches) in dealing with chronic pain patients on an individual as well as on a community basis. Finally, the last section will outline some concluding remarks as well as future directions related to chronic pain research.

1. Chronic Pain: Conceptualization

The concept of chronic pain has been recognized and studied since antiquity. Historically, etiology of chronic pain has lied within different mystical, spiritual, and religious structures. Western thinking has been influenced by religious explanations of chronic pain, with pain conceptualized as a punishment inflicted by God for sins committed by the sufferer. In fact, the word pain is derived from the Latin word peona, meaning punishment. It was further believed at that time that the heart was the center of sensation and that pain was the result of increase in the sensitivity to touch, which was carried by the blood to the heart (Todd, 1999). This interpretation of pain was the predominant one in the Western world until it was replaced by Descartes' hypothesizing that the brain was the center of sensation and that pain was transmitted by means of threads running from the skin to the brain. With the identification of specific pain receptors in the periphery of the brain and pathways from the periphery to the brain, Descartes' hypothesis was supported (Todd, 1999).

With the expanded knowledge of pain mechanisms, there has been an increased focus on the psychological aspects of pain. For example, Hardy and associates (1952) claimed that pain perception is based on a neurophysiological process involving specialized neural receptors and conductive pathways for pain. They also claimed that while the reception process seems to be similar and constant for all individuals, reaction to pain is influenced by past experience, social setting and psychological factors, all of which account for the wide variability that is observed in response to pain. Similar point of views in which the roles of psychological, cultural and social factors became an integral part of the conceptualization of pain were articulated by other prominent scientists at that time (e.g., Engel, 1959; Melzak, 1973; Szasz, 1957).

The committee on taxonomy for the International Association for the Study of Pain defined pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage” (Mersky, 1991). In addition, it was also stated that “pain is always subjective and that each individual learns the application of the word through experiences related to injury in early life”. According to this committee, experiences that resemble pain, such as “prickling”, but which are not unpleasant, should not be classified as pain. Their definition attempts to account for earlier concepts of pain, particularly the subjective nature of pain, the past learned experiences, and the physical as well as emotional meanings (Mersky, 1991). Widespread acceptance of this perception-based definition of pain has led to many recent advances. Innovative classifications of pain syndromes, more elaborate diagnostic frameworks, and an increased search for effective treatments have benefited from defining pain as a subjective phenomenon. Such advances would not have occurred if the definition of pain would have been limited by the occurrence of a proximate stimulus (Von Korff et al., 1992).

There is often the tendency to confuse the assessment and management of acute pain with that of chronic pain. As such, it is important to understand some of the basic differences in the presentations, characteristics, and phenomenology of acute and chronic pain. Before, however, it would be helpful to briefly describe some of the prevalent theories of pain perception.

1.1 Theories of Pain Perception

Three main theories of pain perception have been adopted by scientists throughout the 20th century. The first of these, the specificity theory, described that free nerve endings, nociceptors, are activated by mechanical deformation, chemical stimuli or extreme temperatures, and generate pain impulses carried by A-delta and C-fibers in peripheral nerves to the spinal cord. These fibers ascend in the ipsilateral tract, cross in the spinothalamic tract, ascend further to the thalamus, and finally terminate in the cerebral cortex to produce the sensation of pain (Tyrer, 1992).

The second of these theories, the pattern theory, proposed that pain is “a sensation resulting from spatio-temporal patterns of nerve impulses originating from nonspecific receptors rather than an individual stimulus-response phenomenon” (Tyrer, 1992). The stimulus enters the spinal cord through the dorsal root ganglia, effects an activation of some cells (T cells) in the dorsal horn which, in turn, transmit an impulse to the brainstem and the cerebral cortex. Furthermore, feedback mechanisms communicate information from the lower to the higher brain centers and vice versa. Such a theory of pain enabled the development of the duality concept of pain consisting of perceptions and reactions.

Both the specificity and the pattern theories of pain contained, however, serious deficiencies. On the one hand, specificity theory was unable to explain pain in the absence of a specific input, such as phantom limb pain. On the other hand, although the pattern theory attributes initiation and persistence of pain patterns to the activity of the brainstem or spinal cord nuclei, neuroanatomical evidence of such centers is lacking (Tyrer, 1992).

Melzack and Wall (1965), in an attempt to combine both of these theories, developed the most accepted theory to date, the gate control theory of pain. According to this theory, pain due to noxious stimuli transmitted through peripheral fibers was subject to the interaction of three spinal cord systems, which could be modified centrally. Peripheral fibers comprise two parallel networks composed of small (facilitators) and large (inhibitors) fibers. Certain fibers respond solely to injury, whereas others increase their reactivity with the intensity of the noxious stimulus. Other cells localized in the substantia gelatinosa in the dorsal horn of the spinal cord act as a gate to incoming stimuli, modifying these impulses (increase or decrease their intensity) prior to transmitting them to the T cells in the dorsal horn. The activation of the Tcells, in turn, are responsible for perception of and response to pain. This process is influenced by other fibers ascending to and descending from the brain which can greatly modify the transmission and perception of noxious stimuli. Since the gate theory to pain was first elaborated, research has accumulated making it clear that pain is a much more complex phenomenon that cannot be fully explained by any single system conceptualization (Tyrer, 1992).

1.2 Acute and Chronic Pain

Acute pain is of recent onset and of relatively short and variable duration (France, Krishnan, & Houpt, 1988). When associated with injury or tissue damage, the pain diminishes progressively with the healing process. Acute pain may occur in different nonpathological states that are not due to disease such as childbirth pain and exercise pain. Acute pain more often occurs, however, with a pathological state or tissue damage. Pain is the symptom of a disease or injury that motivates the individual to seek some kind of treatment. Besides warning the individual that something is wrong, pain also prepares the individual to cope with a disease or injury. As a matter of fact, some held that pain is associated with recovery, reinforcing rest in the injured person in order to promote healing (Wall, 1969). In addition, behaviors initiated by pain are strongly influenced by past learned experiences, social-cultural settings in which pain and injury occur, the psychological state of the individual during the onset of pain, as well as that person's personality. There is usually a strong correlation between the location, type, and severity of pain and the disease process or injury. The duration of the pain can be predicated when the cause of the pain is known. Moreover, the patient expects the pain to diminish as the illness or injury resolves. Finally, anxiety uniformly occurs in acute pain states. The autonomic reactivity of sympathetic hyperactivity in acute pain and anxiety are identical. Among such autonomic changes we find tachychardia, increased peripheral blood flow, increased systolic and diastolic blood pressure, increased muscle tension and sweating, and decreased release of cathecolamines (Niv & Devor, 1999).

Chronic pain is most often defined as the daily occurrence of pain over an extended period of time (> 6 months). This condition most commonly occurs in headache, back pain, arthritis, cancer, and certain psychiatric disorders such as major depression, anxiety disorders, hypochondriasis, and psychogenic pain disorder (Niv & Devor, 1999). Chronic pain persists despite the intervention of medical treatment and the passage of time. Explanations for the presence and continuation of the pain are hard to come by, and the course of such a condition is often unknown. Furthermore, the anatomical, physiological, and biochemical pathology identified by physical examination and diagnostic tests do not adequately explain the persistence of the pain (Niv & Devor, 1999).

In contrast to patients with acute pain, those with chronic pain display little autonomic hyperactivity. On the contrary, they tend to exhibit neurovegetative symptoms such as altered appetite and weight, disrupted sleep, decreased energy and libido, diminished concentration and increased irritability. Such patients usually have a history of medical and surgical interventions targeting the relief of pain. Not surprisingly, the associated emotional distress, family disturbance, economic stress and altered lifestyle become significant problems in themselves. The longer patients suffer from chronic pain, and the more psychological and social factors seem to influence the course of the syndrome. In addition to exhibiting increased irritability, chronic pain patients show signs of social withdrawal, increased inactivity and psychological distress (Niv & Devor, 1999).

The etiology of pain has often been dichotomized as either of organic or of psychogenic nature. This categorization ignores that the development and the persistence of pain are often secondary to a complex interaction of organic and psychological factors. An individual's pain threshold can be influenced by some psychological states (e.g., anxiety, depression), and by some disorders (e.g., psychosis, bipolar disorders) (Gamsa, 1994). Fatigue, insomnia and suggestion can also alter pain threshold. Certain medications such as benzodiazepines, barbiturates, meprobamate, narcotics and antidepressants can also affect pain threshold (Arnoff & Gallangher, 1999). It should be emphasized, however, that a factor that alters pain threshold may not necessarily alter pain behavior or complaints in the same direction. For example, despite research findings suggesting that depression increases one's pain threshold, pain complaints are frequent symptoms of the depressive syndrome (Krishnan, France, & Davidson, 1988). It seems that the presence of secondary gains factors, insomnia and fatigue will increase pain complaints, whereas reassurance and distraction will minimize pain complaints. Control of pain stimuli, suggestion and cognitive strategies may have conflicting effects on pain complaints. Uncertainty, anxiety and increasing age are all associated with increased pain complaints. Finally, use of antidepressants, antianxiety agents, opiods analgesics and acute administration of sedatives/hypnotics will decrease pain complaints, whereas prolonged use of sedatives/hypnotics will increase pain complaints. Such relationships among pain threshold, pain complaints, and related behavior are very interesting but may be limited in clinical practice (Krishnan, France, & Davidson, 1988).

2. Chronic Pain: Assessment

Given the growing data base on the epidemiology of chronic pain, more comprehensive assessment procedures have been developed. The assessment of the patient with chronic pain includes the evaluation of physical, psychological, social and cultural factors. It is extremely important to assess the contribution of all these dimensions in the assessment of chronic pain. A comprehensive assessment involves obtaining a clear description of the nature of the pain, previous personality and level of medical and psychological functioning as well as an accurate evaluation of disabilities (Kulisch, & Baker, 1999).

One of the first steps in the assessment of chronic pain is to distinguish between acute and chronic pain. Although already defined, clinicians should be aware that psychosocial factors rarely cause acute pain. When left untreated, however, acute pain can lead to psycho-social consequences. Chronic pain, on the hand, is of longer duration and is strongly related to psychosocial factors. Once a diagnosis of chronic pain has been made, clinicians should be extremely careful not to consider all chronic pain patients as an homogenous group. One's response to chronic pain varies considerably and seems to depend more on the coping skills than on tissue damage, medical diagnosis, or location of the pain complaint. In other words, psychological factors seem to be the best discriminators within a chronic pain population (Jamison, Rudy, Penzien, & Mosley, 1994).

2.1 Psychological Assessment: Goals

Given that the goal of a psychological assessment include prediction of behavior and data gathering for structuring an effective psychological and medical treatment strategy. This type of assessment can also serve to screen the patient for psychosocial factors that can affect treatment outcome, particularly of medical nature. Furthermore, psychological assessments can be used to predict the likelihood of reinjury, of returning to work, and provide estimates of health care utilization. Another focus of this type of assessment is the identification of deficits and abilities, often required for resolving worker compensation claims. When taken repeatedly, such measures can serve to assess improvements across time. Among the factors that are more probable of showing pain are depression, focus on somatic symptoms, sleep, job satisfaction, and perceptions of control or mastery over pain and disability. A DSM-IV diagnostic can be assigned as well (Turk, Rudy, & Sorkin, 1993).

2.2 Psychosocial Factors: Evaluation

2.2.1 Chronic Pain: Rating Pain Intensity

Research has demonstrated that pain intensity measures are reliable, valid and useful. Pain intensity tends to change over time and is influenced by various environmental factors. The most commonly used self-reports of pain intensity are the Visual Analog Scale and the McGill Pain Questionnaire. To render these tools more valid, it is recommended to increase their administration to 3 times a day for a minimum of 4 days to get a better idea of the average pain intensity felt by the patient. Once this is achieved, the clinician can make use of the data generated by these questionnaires in order to better distinguish between different pain syndromes. Such knowledge is necessary before the other steps of the assessment process can take place (Jensen & McFarland, 1993).

2.2.2 Chronic Pain: Depression and Anxiety

Within chronic pain individuals, the incidence of depression has been shown to exceed 80%, with studies indicating that over 50% of chronic pain patients develop major depression (Holroyd, France, Nash, & Hursey, 1993). Of those diagnosed with a major depression, from 50 to 60% have a second depressive episode and close to 15% of these patients will die from suicide. Research has consistently demonstrated the high correlation between scores on depression and the presence of pain and disability (Holroyd, France, Nash, & Hursey, 1993). Although some have even tried to prove a causal relationship between depression and chronic pain, it is more commonly acknowledged that these two variables interact and mutually affect each other (Holroyd, France, Nash, & Hursey, 1993).

In evaluating for depression in chronic pain patients, one should consider the individual's belief system in order to better understand how the patient perceives his life (e.g., perceived control), his condition (e.g., perceived impact), and both. The assessor should, however, use the DSM-IV (1994) diagnostic criteria to adequately diagnose for depression. A multitude of respondent (e.g., Beck Depression Inventory) as well as investigator-based (e.g., The Hamilton Rating Scale for Depression) measures exist to assist the evaluator in the assessment process (Kerns & Jacob, 1992).

The other commonly observed condition in patients with chronic pain is that of anxiety. The correlation between anxiety and chronic pain is well documented with anxiety contributing to symptoms and as a consequence of acute and persistent pain (McCracken & Gross, 1993). According to some authors, 95% of chronic back patients report anxiety symptoms before onset of an episode. Furthermore, a strong correlation seems to exist between anxiety and depression. Psychophysiologically, increased anxiety lowers the pain threshold so that the patient can better identify and then reduce or eliminate the pain. Similarly, in assessing for anxiety, clinicians should base their diagnosis on the DSM-IV criteria. They can, nevertheless, make use of the different self-report measures of anxiety such as the Brief Symptom Inventory and the Spielberger State/ Trait Anxiety Inventory (Kerns & Jacob, 1992).

2.2.3 Chronic Pain: Beliefs & Behaviors

A chronic patient's beliefs about pain and treatment and perception of disability are strong predictors of functioning and disability. Those who believe that they can control their pain, avoid catastrophizing, and believe that they are not severely disabled show greater improvement (Shutty, DeGoot, & Tuttle, 1990). In addition, treatment compliance is often related to the patient's beliefs relating to the efficacy of the treatment plan. This said, by assessing the patient's belief system concerning his/her coping abilities, the clinician can better evaluate the patient's perceptions of the condition, his/her compliance with the program and the treatment success (Shutty, DeGoot, & Tuttle, 1990).

Several self-report measures are available to assist the evaluator to assess the patient's belief system. Among those are the Survey of Pain Attitudes, the Attributional Style Questionnaire and the Pain Beliefs and Perceptions Inventory (Shutty, DeGoot, & Tuttle, 1990). Other questionnaires exist to asses the patient's perception of disability (e.g., Sickness Impact Profile, Oswestry Disability Scale). Items from such questionnaires assess the patient's perception of disability, as well as social and perceived mental health functioning (Shutty, DeGoot, & Tuttle, 1990).

While the patient's belief system are being assessed, his/her behaviors should also be considered. To understand the patient's behaviors, the evaluator must consider overt behaviors, cognitive and affective responses, as well as physiologic response patterns (Tyrer, 1992). Behavioral assessment methods are numerous and have proven to be very effective. Among the assessment strategies are: (1) more systematic methods for observing and recording nonverbal expressions of pain, (2) methods for evaluating how patients cope with pain, (2) psychophysiological approaches to assess the impact of stress on pain, and (3) more sophisticated measures of pain perception (Tyrer, 1992). These measures allow to identify behavioral concerns of chronic pain patients more objectively and more precisely. In addition, such measures provide a data base which can be used by professionals to make educated decisions about surgical, medical and psychological interventions. Moreover, such measures often help to delineate the role that environmental, social, and intrapersonal factors play in controlling pain behavior. Finally, behavioral assessments allow to identify and to target specific behavioral problems lively to respond to behavioral pain management. Their early identification can prevent them from becoming entrenched and accelerate the patient's return to his normal activities (Tyrer, 1992).

A comprehensive behavioral assessment is necessary to identify behavioral problems in patients and to better understand the psychological and behavioral factors that may affect those problem behaviors. The assessment process often begins with a structured interview designed to identify the patient's presenting behavioral problems. Once this is achieved, more detailed information is gathered using five different assessment measures: self-monitoring, standardized pain behavior observations, psychophysiological analyses (e.g., electromyographic measures during rest and stress episodes), a pain coping skills questionnaire, and standardized measures of psychological distress. More specialized psychological tests are also requested for some patients (e.g., intelligence testing). Finally, all the data gathered is integrated in order to better select a treatment intervention for the chronic pain patient (Tyrer, 1992).

2.2.4 Chronic Pain: Somatization

Chronic pain patients often focus excessively on symptoms. This behavior is often debilitating and often leads patients to seek out multiple treatments. The chronic disability and the recurrent course of chronic pain often reinforce the patient's focus on symptoms and lead him/her to further consult and undergo medical interventions, including repeated surgeries, in order to reduce the pain that is felt. When the patient's complaints are not exclusive to pain, a diagnosis of a somatization disorder should be considered (Bacon, Bacon, Atkinson et al., 1994). These patients often have poor outcomes with the somatically focused interventions. On the positive side, behavioral and cognitive interventions aimed at reinforcing positive cognitions and eliminating negative ones tend to better fit somatization patients. In fact, some researchers report a much higher incidence of somatization disorder in pain populations (Bacon, Bacon, Atkinson et al., 1994). In addition, research seems to indicate that major depression as well as alcohol dependence are related to increased somatization (Bacon, Bacon, Atkinson et al., 1994).

Multiple measures exist to assist the clinician evaluate somatization disorder (SCL-90) with chronic pain patients. The Multiphasic Minnesota Personality Inventory (MMPI-2) is also commonly used to assess oversomatization, focusing on elevations on the Hypochondriasis and Hysteria subscales. Caution should, however, be used in diagnosing for somatization because much of the item content on the different scales overlap with medical content (Bacon, Bacon, Atkinson et al., 1994).

When a somatization disorder is considered, the concept of secondary gains often surface. The gains relate to the increased attention, emotional and instrumental, that the patient receives from others. Other gains can relate to a financial motivation increasing disability behavior. One should be cautious, however, not to discredit the patient's pain and to directly forward the secondary gains hypothesis (King, 1994). As such, the evaluation process should address reinforcing factors (e.g., pain complaints), and psychological, physical and social processes influencing pain perception. A treatment plan should then be developed in which pain self-management is reinforced and behaviors and cognitions which are dysfunctional are abolished (King, 1994).

2.2.5 Chronic Pain: Personality and Coping Styles

Many researchers have pointed out that a patient's behavior patterns and coping styles are important in predicting treatment course with chronic pain patients. Maladaptive behavior patterns and negative personality factors affect one's coping with pain and with medical management. In fact, Gatchel (1996) has reported that over 50% of chronic pain patients met psychiatric diagnostic criteria for different personality disorders. One the most common of these personality disorders is certainly the borderline personality disorder (33% of all personality disorders). As such, in evaluating chronic pain patients, it is important to screen for personality disorders, for they often are disruptive factors in treatment compliance as well as success (Gatchel, 1996).

2.2.6 Chronic Pain & Trauma

Emotional trauma and sexual abuse also need to receive a lot of attention in the assessment of chronic pain. In fact, reports suggest that a higher proportion of sexual abuse victims is found in chronic pain populations than in the general population. No causal link, between trauma and chronic pain has been delineated as of yet. What is known so far is that trauma survivors often resist treatment for chronic pain, and as such treatment with such patients tends to be less effective in general. As such, attending to such factors seems to be important in order to better predict patient's compliance with treatment (Wurtele, Kaplan & Keaimes, 1990).

2.2.7 Chronic Pain: Socio-cultural Factors

The evaluator should attentively consider the role held by the patient's significant others or primary caregivers. Results suggest that oversolicitous significant others, particularly the patient's partner, often lead the patient to increase overt pain behavior and complaints. This said, the patient's spouse is often an important person to include in the assessment whenever possible. To assess for solicitousness, the clinician can use one of the scales of the Multidimensional Pain Inventory (Turk, Rudy, & Sorkin, 1993). In addition, research seems to indicate that a family member's dissatisfaction or satisfaction with the patient's condition provides a basis for evaluating prognosis or the focus of treatment, as well as the family's willingness to support the patient's treatment program is important (Turk, Rudy, & Sorkin, 1993). In addition, one should attend to other socio-cultural factors that can affect the patient's prognosis (e.g., religious beliefs related to pain or to pain treatments, financial gains, poverty), and should exercise increased sensitivity when dealing with such issues (Turk, Rudy, & Sorkin, 1993).

2.2.8 Chronic Pain: Work experience & Job Satisfaction

Personal and work history, as well as the employer's impression on the patient's work performance and willingness to return to work, are all valuable data to gather in order to determine prognosis and treatment plan. Lack of job satisfaction, for example has been identified as a risk factor for new episodes of back pain (Poppel, Koes, Devillé, Smid & Bouter, 1998). If work offers little reinforcement to the patient, unsuccessful return to work is likely. In fact, return to work rates are estimated at 65% but the mere presence of psychosocial concomitants of pain has been shown to predict even poorer outcome. The assessor can use job satisfaction questionnaires as well as occupational stress questionnaires in order to assess a source of resistance to return to work that is not necessarily reported by the patient (Poppel, Koes, Devillé, Smid & Bouter, 1998).

2.2.9 Chronic Pain: Litigation

Numerous studies have demonstrated that litigation is a predictor of disability, increased plain complaints, disability and treatment failure. Those who seek compensation report greater psychological distress, higher self-report of disability and greater pain than those who do not seek compensation. Whereas financial gains seem to be the motivating factor for the exaggeration of such behaviors, one should be cautious in accusing a patient with malingering, a DSM-IV diagnosis that is extremely difficult to document and support since volition cannot really be measured. Finally, while malingering is quite rare, success with any treatment is often affected by fears of financial ruins, job satisfaction, anger at others (particularly those thought responsible for their injury). In turn, it is recommended that in order to be more effective, a treatment intervention must involve those who influence the patient's treatment (e.g., nurse, employer, attorney, insurer) (Block, 1981).

3. The Epidemiology of Chronic Pain

Epidemiological studies have shown that chronic pain represents a major public health concern (Becker et al., 1997; James et al., 1991; Von Korff et al., 1988). Although the evidence is now overwhelming, epidemiology research still needs to contribute a lot to better understand this condition.

3.1 Incidence

The incidence of chronic pain is elevated. In Britain, for example, about 2.2 million people a year consult for a back pain. This represents close to 5% of the population of Britain. Moreover, the incidence of chronic back pain at any one time is certainly higher than this (Tyrer, 1992). While other incidence rates are presnted, they seem to vary considerably across populations and localization of pain, and as such should be delt with in a more specific basis (Tyrer, 1992).

In those with psychological and/or psychiatric problems pain is present more frequently. In general, close to 50% of psychiatric outpatients spontaneously complain of pain during their illness. The incidence of pain in inpatients with psychiatric problems is somewhat less than this, at more or less 40%. Furthermore, a similar percentage of patients with pain arising from medical conditions have psychiatric problems. This suggests that pain and psychological distress as closely related (Tyrer, 1992).

3.2 Prevalence

Epidemiological studies of pain have mostly focused on determining how many people suffer from chronic pain and on how the frequency varies when factors such as age, sex, and racial and social group are considered. One main problem with such studies is that their estimates of the prevalence of chronic pain ranges between 7% and 40% (Verhaak et al., 1998). Many reasons have been provided to explain for this discrepancy. Among those is the different definitions of pain that were used in these studies. Some researches have included any kind of pain while others have excluded fleeting and minor pain (Von Korff et al., 1988). The consequences of using differing definitions were outlined by Von Korff and associates (1988) who reported that while 37% of respondents reported recurrent pain, only 8% has severe and persistent pain and less than 3% had had severe and persistent pain lasting more than 6 days.

The distribution of pain seems also to vary within the community. Some studies reported that the prevalence of chronic pain increases with age (VonKorff et al., 1988). Furthermore, despite little research supporting gender differences in prevalence rates, chronic pain is often thought as more common among women. A more thorough investigation of gender differences, however, revealed that significant differences were only observed when pain in specific body sites was investigated (Von Korff et al., 1988).

Such studies of pain prevalence require clear and consistent definitions so that meaningful and interpretable results can be obtained. Prevalence studies, for example, can be used for planning health care services or to estimate the need for special treatment facilities. Unfortunately few studies have been capable of offering such information. What is needed is information on the nature of pain problems in the community, the effectiveness of their current management, and the types of health care facilities that are required for optimal care to be offered (Brattberg, 1990).

Given the complex nature of chronic pain, prevalence cannot be measured by means of assessing well-circumscribed physical conditions, as with other diseases such as diabetes. Chronic pain requires a multidimensional approach consisting of different dimensions such as pain intensity, localization of pain, temporal characteristics, affective appraisal, coping and grading of pain (Brattberg, 1990). Yet despite these enumerated difficulties, statements have been made about the prevalence and the costs and impact on social security system of chronic pain. In fact, based on current research, it is not possible to give a reliable estimate of the prevalence of chronic pain.

In order to better understand the research base accumulated to date, Verhaak and colleagues (1998) undertook a meta-analysis to better estimate the prevalence of chronic benign pain disorder among adults. Their search identified 15 empirical studies which had assessed the prevalence of chronic pain in general population. They reported that the identified studies differed in terms of their research methods (telephone survey, postal questionnaire, interview, and expert assessments) and their definitions of pain. In some studies pain was defined in terms of its intensity, whereas in others it was defined in terms of its duration (e.g., >24 hours, > 1 month, > 3 months, > 6 months) or of illness behavior. None of these studies, however, defined the concept of benign explicitly.

In terms of reported prevalence rates, they seem to range from 2% to 40% with a median of 15%. An integration of these studies seems to indicate that the prevalence rates were not greatly affected by the method of data collection nor by the time definition of chronic pain. In other words, studies in which chronic was defined as persistent pain for longer than two weeks did not report significantly higher rates than those in which chronic was defined as persistent pain for 6 months or longer. In addition, prevalence estimates provided through general practitioners did not differ from those observed by way of direct interview, postal or through telephone contact.

The authors were not able to determine, however, the exact prevalence rate of benign chronic pain. Certainly many people suffer from pain to such an extent that they are limited in their activities. As mentioned, the reviewed studies yielded a median prevalence rate of 15%, with a range from 2 to 40%. In addition, it seems that patients that suffer from chronic pain are: “relatively often middle-aged women from lower socioeconomic status. Low back, neck, and shoulder are the body areas most frequently affected. Chronic pain is often associated with depression or other kinds of psychological distress.” The authors remain cautious in providing explanations for the wide range of prevalence rates observed, but they do state that a prevalence of chronic pain of 10% of the population seems a very conservative estimate.

In relation to the benign part of chronic pain, few conclusions can be drawn in reference to the extent to which somatic diseases are responsible for the reported chronic pain. As stated, low back, neck, and shoulder pains were the body sites most frequently affected. These results are somewhat in line with those reported by Frolund and Frolund (1986). These authors indicated that the most important chronic pain categories were ‘bone/joint' pain (24% of all chronic pain conditions), ‘muscle/ligament' (17%), ‘low back' (13%), ‘headache' (12%), and ‘gastrointestinal (11%). Over 53% of chronic pain patients seem to suffer from symptoms of pain rather than from demonstrable disease. The predominance of low back pain and chronic back pain reported in another study suggests similar findings. The positive relation between chronic pain and psychological distress also points to the benign or not organically explained character of pain in many cases. Finally, although this study helped to integrate the study accumulated to date, many other questions remain unanswered. More specifically, little is still known on the course of several aspects of pain, the disabilities it causes, the medical treatment sought, the costs involved, the behavioral aspects (e.g., coping), and the impact on physical an psychological well-being. On the positive side, researchers should now be aware of the different and important dimensions that need to be considered in order to arrive at more precise as well as usable data.

3.3 Prevention

Epidemiology is defined as “the study of distribution and determinants of health-related states or events in specific populations, and the application of this study to control health problems” (Last, 1988). This said, the primary goal of epidemiology is to identify the causes of disease so that they can be prevented. In order to elucidate the causes of disease, the field of epidemiology provides a variety of tools of which the most powerful, case-control studies and prospective studies, have rarely been used in the study of chronic pain (Crombie, 1994). By way of such research designs, researchers were able to demonstrate that smoking was the major cause of cancer and that increased serum cholesterol levels raised the risk for hart disease. Findings provided from such studies have provided the foundation to different health community education campaigns targeting disease prevention (Crombie, 1994).

There are different types of preventions strategies that are used to deal with chronic pain, but many more should be considered. The first of the three types of preventions, primary prevention, targets preventing the occurrence of a disease (Last, 1988). One such example is the use of pre-operative analgesia to prevent the development of phantom limb pain in amputees (Back, Noreng & Tjelden, 1988). Such potential to prevent should not be limited to amputation since other conditions such as throcotomy and mastectomy can also result in chronic pain. According to some researchers, if the specific interventions that cause pain during the operation could be pinpointed, a modification of the procedures that cause pain can lead to the primary prevention of chronic post-operative pain (Back, Noreng & Tjelden, 1988).

Another example of primary prevention is illustrated in the study conducted by Poppel, Koes, Devillé, Smid and Bouter (1998) who examined the relationship between physical and psychological risk factors and the occurrence of a new episodes of back pain in workers who were not suffering from chronic pain at testing. Using a prospective design, with a 12 months follow-up, 270 cargo workers of a Dutch airline company, who reported no back pain at baseline and whose tasks included loading and unloading of heavy material, participated in the study. Three intervention groups (lumber support only, education on lifting only, and education combined with lumbar support) a control group were formed. The interventions did not have any effect on the incidence of back pain or sick leave du to back pain, and as such were not considered in the remaining of the analyses. Data was gathered by way of weekly questionnaires and behavioral testing assessing the occurrence of a new episode or of sick leave due to back pain, as well as individual factors (e.g., history of back pain, smoking, abdominal muscle strength and endurance, exercise, activity levels) physical factors (e.g., riding forklift truck, manual lifting tasks), and psychological factors (e.g., job satisfaction, opinion on work). Results indicated that during the 12 months testing period, 31% developed a new episode of back pain and 11% reported sick leave due to back pain. By way of multiple regression logistic analysis, it was observed that the best predictors for the occurrence of another back pain episode were information on the history of back pain (Odds Ratio = 9.8), and low job satisfaction (Odds Ratio = 1.2). In addition, riding a forklift truck seemed to be a protective factor for the occurrence of back pain (Odds Ratio = 0.7). The authors of the present study state that although future studies need to confirm the obtained results, by increasing job satisfaction and targeting particularly individuals with some history of back pain. Such interventions are believed to lead to a reduction in the occurrence rate of chronic back pain in this case.

Finally, Fordyce, Brockway, Bergman, and Spengler (1986) assigned acute back pain patients to either a traditional or a behavioral treatment program. Those in the traditional program were told to let pain be their guide in using 4 treatments (analgesics, instructions in activation, exercise, and return visits). Patients in the behavioral protocol received the same treatments but on a time contingent basis: Analgesic taken at fixed intervals, activity limits were time specified, and the number of exercise and return visits was set. At a 12 month follow-up, the behavioral group had returned to pre-injury levels of functioning whereas the traditional treatment group had significant increases in claimed physical impairment.

The second of the three types of preventions, secondary prevention, involves the early detection of disease so that prompt and effective measures can be undertaken to minimize ill-health (Last, 1988). One such example is provided by Bowsher (1993) who described that treatment for neurogenic pains were significantly more successful when early detection and treatment were possible. In another study, Linton, Bradley, Jensen, Spangfort, and Sundell (1989) demonstrated that early intervention among nurses with low back pain led to significant improvements in health. More specifically, this study investigated the effectiveness of a secondary prevention program for nurses with back pains who were likely to develop chronic pain. A treatment group (N =36) was compared to a control group (N = 30) on three repeated occasions dispersed over 6 months. Whereas the control group was placed on a waiting list, the treatment group received both physical and behavioral interventions in order to reduce current problems and particularly to prevent reinjury and minor pains from attaining a chronic state. On the one hand, physical interventions involved program activities as well as physical therapy for 8h/day during a 5 week period. On the other hand, behavioral interventions were introduced, twice per week during a 5 week period, to help the participants learn to better control their pain, and to help them maintain healthy, low risk life styles that would reduce the probability of injury and reduce the effects of acute pain sensations. These behavioral techniques were taught by a psychologist who developed a program aiming pain control (e.g., relaxation, coping strategies), life style management (e.g., behavioral goal-setting training, self-rewards for maintaining healthy behaviors), risk analysis (e.g., identify high-risk injury situations), and application training (e.g., practice of maintaining these behaviors). Results demonstrated that, in comparison to the control group, the treatment group improved significantly and lower levels of pain intensity, anxiety, sleep complaints, fatigue, absenteeism, observed pain behaviors, helplessness and mood were observed and reported. In addition, the same differences were observed 6 months after the first set of measures were taken. Overall, results from this study seem to indicate that such a secondary prevention program targeted at altering life style represents an effective method for dealing with musculoskeletal pain problems. Once such secondary preventive measures have been implemented and additional risk factors identified, more effective primary prevention programs can be developed.

The last of the three types of preventions, tertiary prevention, targets a reduction of suffering from irremediable conditions (Last, 1988). In other words, these strategies involve preventing the development of pain related behavior and of psychological illnesses in chronic pain patients. One such example, is an intervention aimed at preventing the chronic pain-depression cycle from occurring. According to Doan & Wadden (1989) chronic pain patients often are clinically depressed and therefore interventions should target the early detection of depressive states in order to prevent the occurrence of clinical depression. Researchers would benefit from further studying the relationships between chronic pain and other psychological illness (e.g., anxiety, psychosis) or maladaptive pain related behavior (e.g., excessive exercise or excessive inactivity) in order to develop other tertiary preventive measures for chronic pain.

Many believe that, so far, epidemiological research has not realized its potential in reducing suffering from chronic pain patients. The challenges for epidemiological research remain numerous. An important one is to identify the individuals for whom preventive strategies would be beneficial and appropriate. To achieve such goals epidemiological studies need to use more rigorous research methods. Standard definitions of pain need to be developed and used in studies which focus on specific syndromes rather than on broad conditions. In addition, the identification of the causes of pain and of related behavior should be the target of greater research. Finally, data needs to be gathered in order to advance the quality and quantity of pain services and to reduce individuals' suffering from chronic pain (Becker, Thomsen, Olsen, Bech, & Eriksen, 1997; Linton, Bradley, Jensen, Spangfort, & Sundell, 1989).

4. Chronic Pain: Advances in Treatment

Over the years, numerous treatment interventions have been used to relieve individuals from chronic pain. Among those the most commonly cited are the pharmacological, the physical and the psychosocial treatment approaches. Other treatments that are used include hypnosis, acupuncture and other forms of alternative medicines such as homeopathic medicine (Aronoff, & Gallager, 1999; Keefe & Williams, 1989).

Although widely used, many of these treatment interventions have yet to be proven as effective agents in the management of pain. In fact, little research has been targeted to assess the relative efficacy of the various main stream interventions. As such, physicians, psychiatrists, psychologists, physical therapists, and other professionals remain uncertain as to the most appropriate treatment that should be used, that is the one which serves the patient best and that is the most cost-effective in the long run (Keefe & Williams, 1989).

Patients with chronic pain have multiple problems. It is therefore unreasonable to expect that one physician be able to understand, diagnose and attain optimal treatment of all disease processes that may represent chronic pain. It is not surprising that the concept of a multidisciplinary pain clinic has been developed, where different specialists work as a team to assess and treat chronic pain. Such clinics often take different forms yet in every case the aim is the same: the relief or reduction of pain by way of the most effective methods available. It is important, however, to understand that pain clinics are often viewed as a last resort. The overall efficacy of a pain clinic is dependent upon it being multidisciplinary in its approach. In such a context, patients are often more willing to accept psychiatric, psychological and social evaluation when it is considered as an integral part of the treatment package. Moreover, to reduce the costs involved in treating chronic pain patients, the different interventions practiced are often given in group formats rather than on a one to one basis (Keefe & Williams, 1989).

As such, this last section will review some of the: (1) mainstream approaches in the treatment of chronic pain, particularly the psychosocial and pharmacological approaches, as well as (2) treatment outcome studies evaluating the effects of different treatments of chronic pain.

4.1 Psychosocial Approaches: Behavioral and Cognitive Treatments of Chronic Pain

4.1.1 Behavioral Treatment of Chronic Pain

Behavioral treatments are concerned with changing the behavior of the patient. The assumption on which behavioral interventions are based is that behavior is directly related to its consequences. Behaviors that are followed by pleasurable or reinforcing experiences are more likely to be repeated whereas those that are not rewarded or which have unpleasant consequences are likely to be reduced. Such conditioning principles have important implications for pain behavior. On the one hand, these are reflected in relation to organic pain in which behavior results from noxious stimuli that occurred previous the onset of pain. On the other hand, operant pain behavior is that which occurs as a result of reward or partial relief from pain. Assessment of pain behavior therefore involves determining how far each of these factors contributes to the patient's presentation of pain. In other words, how far pain behavior is governed by the consequences of that behavior rather than physical nociceptive factors. The type of treatment selected will depend on the contribution of these factors (Gil, Ross, & Keefe, 1988).

Numerous behavioral techniques applicable to the management of chronic pain exist. The four that are the most frequently used are: (1) the operant conditioning protocol, (2) the psychophysiological protocol, (3) the conditioned fear response protocol, and (4) the muscle reeducation protocol. Although these treatment approaches will not be presented here, one should know that the conceptual background as well as the treatment phases of each of these protocols is different. For example, the operant conditioning protocol emphasizes the patient's behaviors and the socio-environmental responses to that behavior, whereas the psychophysiological protocol emphasizes the importance of stressful environmental events in eliciting psychological and physiological responses that cause pain. As such, one should be familiar with these different protocols in order to better understand how and when to implement them or not. These four protocols are reviewed in a more comprehensive fashion by Gil, Ross, & Keefe (1988).

4.1.2 Cognitive Treatment of Chronic Pain

Cognitive therapies to pain management are concerned with the way the pain sufferer thinks about his pain. These thoughts involve beliefs about the causes of the pain, the threat of illness and incapacity, and the effects of treatment. Thoughts determine the kind of help that is sought and which treatments will be accepted and they affect the mood of the sufferer, and the ways one copes with the pain. Often, some of the thoughts and beliefs held by chronic pain patients are not accurate or to say the least are disadvantageous. The aim of the cognitive intervention is to identify, challenge and reprocess the unhelpful cognitions of chronic pain patients. Although there may still be hope for a cure, with most chronic pain conditions, the goal is to minimize any disability and facilitate adjustment to a new lifestyle with its permanent handicaps (Kuile, Spinhoven, Linssen, & Houwelingen, 1995).

Different techniques are used in cognitive therapy to pain management. Among those, the most important ones are: (1) explaining and understanding the patient's pain, (2) eliminating or reducing negative thinking (e.g., blaming, shoulds, unrealistic control, led by emotions, dark glasses), (3) changing beliefs by listening (e.g., being non-judgmental), (4) teaching intrusive thought stopping techniques, (5) utilizing the ABCD Model of cognitive therapy to identify the activating events, beliefs and consequences in order to dispute them, (6) teaching effective cognitive coping strategies, (7) increasing pain tolerance, (8) promoting an active role in self-management (empowerment), (8) mood management, (9) teaching positive thinking, positive imagery as well as other distraction techniques (Keefe, Dunsmore, & Burnett, 1992; Kuile, Spinhoven, Linssen, & Houwelingen, 1995).

4.2 Pharmacological Treatments of Chronic Pain

In today's society, drug-based interventions are by far the first line of defense against pain symptoms. A variety of drugs are used in the management of chronic pain, each with its own properties and consequences. Although it is the physician's role to prescribe such medications, any other professional involved in the treatment of chronic pain should be familiar with the types of drugs that are used and their related toxicology in order to better intervene with such patients who are often medicated.

Among the pharmacological interventions, the most commonly used are the analgesic-based drugs. Analgesics include the nonsteroidal anti-inflammatory drugs (e.g., aspirin) and the opiod-based drugs (e.g., morphine, codeine, methadone). Other commonly used drugs in the treatment of chronic pain are the psychotropic drugs which aim to better the mood or behavior of chronic pain patients (e.g., antidepressants, neuroleptics) (Aronoff & Gallagher, 1999). This said, different drugs are administered to chronic pain patients, and as such, a better understanding of these drugs is not only helpful but necessary for any professional working with chronic pain patients (Aronoff & Gallagher, 1999).

4.3 Treatment outcome studies: Evaluation of different treatments

Outcome studies evaluating different chronic pain interventions have several goals. The first is to compare these treatments to control conditions, and the second is to test their relative efficacy. In comparing treatment interventions, one must have an appropriate control group. Many studies have compared behavioral treatments for chronic pain with waiting list conditions. For example, Phillips (1987) tested the efficacy of a cognitive behavioral treatment package (relaxation, exercise, activity pacing, and cognitive interventions) by comparing it to a waiting list control condition. Results suggested that over the study period, no changes occurred for the control group, whereas those receiving the treatment showed highly significant changes in mood, affective reaction to pain, self-efficacy, avoidance behavior, drug intake and exercise capacity. Furthermore, these gains were not only maintained at 12-month follow-up, they became actually stronger on all outcome variables. Similarly, Engstrom (1983) compared a cognitive behavioral treatment with a placebo medication condition. Results indicated that chronic low back patients who received cognitive behavioral treatment had significant reductions in pain, as well as increases in internal locus of control. Those receiving placebo, however, failed to show any treatment gains.

To be more rigorous, however, researchers have compared interventions for pain with alternative treatments. For instance, Henrich et al. (1985) compared behavioral therapy with physical therapy in chronic back pain patients. Results demonstrated that both treatments produced improvements in pain and psychosocial functioning. Two differences in outcome were noticed however. Whereas physical therapy improved back protection and control skills more than behavioral therapy, behavioral therapy was better in reducing psychological distress in these participants.

Similarly, Kerns, Turk, Holzman, & Rudy (1986) compared a cognitive-behavioral with an operant conditioning treatment that emphasized training in coping skills. Both treatments significantly reduced health care use when compared with a waiting control condition. Only those receiving the cognitive behavioral treatment, however, showed improvement on self report measures of pain, psychological distress, instrumental activities and dependency.

Finally, Turner & Clancy (1988) carried out a study in which operant and cognitive behavioral treatments for chronic low back pain were compared. They used video-tape observation method to record changes in pain behavior and at a 12 month follow-up. The operant protocol was carefully designed and had an aerobic exercise and a spouse-training component. Posttreatment data showed that patients in both conditions improved significantly on physical and psychosocial disability measures. Furthermore, both groups maintained their improvements at a 12-months follow-up. The rate of improvement, however, differed between these two protocols. The operant condition showed greater initial improvement, whereas the cognitive behavioral group showed steady improvements over the 12 months.

5. Conclusion

Throughout the present paper, a review of chronic pain literature was presented. More specifically, an introduction to the concept of chronic pain according to a biopsychosocial approach was first presented. The assessment process of chronic pain was then detailed with particular emphasis on the multifactorial etiology of chronic pain. Next, the latest epidemiological data of chronic pain was reviewed by focusing on the roles of prevention (primary, secondary and tertiary). Finally, treatment protocols (psychosocial and pharmacological) were presented and their relative effectiveness discussed.

In general, current understanding of chronic pain is less than satisfactory. Yet, dozens of different treatment modalities have been presented, some with little or no merit. Although the effectiveness of some of the mainstream treatments has been more or less tested, much work remains to be done to delineate which treatments should be used with populations differing in age, sex, and type as well as localization of chronic pain. These studies need to be conducted on larger samples and should use more rigorous research methodologies such as indicated previously.

Besides identifying mechanisms that underlie pain, researchers should incorporate a broader range of behavioral, perceptual, and biological measures into their studies. Methods for enhancing maintenance of treatment effects also need to be considered to a greater extent. According to Turk and Rudy (1991), 30 to 60% of chronic pain patients who were successfully treated later relapsed. The variability in outcome seemed to be associated with a high level of noncompliance. As such, it is important that treatment protocols emphasize the role of booster sessions and self-monitoring techniques to increase maintenance.

Finally, such treatments should also aim individuals who do not have easy access to pain programs. Efforts should target the development of models for delivering pain management services in community settings as well as in home-based settings. By extending interventions, a greater impact on pain and suffering may be achieved, and more individuals would benefit from a more active and productive life (Turk and Rudy, 1991).


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Yaniv Benzimra, Ph.D.
Y2 Consulting Psychologist

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