Biobehavioral factors affecting pain and disability in low back pain: mechanisms and assessment.

Low back pain (LBP) continues to represent the leading musculoskeletal cause of disability in the United States and is the most frequently reported condition for which people receive outpatient physical therapy.[1-4] The majority of literature that describes the physical therapist's role in the care of these individuals is based on the premise that identifying and correcting physical impairments will favorably affect the patient's disability.[5-10] This approach is based on the classic biomedical model of disease, which infers a direct positive correlation among pathology, pain, impairment, functional limitation, and disability.[11-13] In certain individuals with LBP, however, especially those whose symptoms have persisted beyond a predictable period of tissue healing, the degree of reported pain, functional limitation, and disability is frequently disproportionate to the observed pathology and impairment.[12,14,15] Traditional methods of physical therapy assessment and intervention are often inefective with these patients. Not surprisingly, the majority of physical therapists prefer to treat patients who have acute pain rather than those with delayed recovery or chronic pain.[4,16] Wolff et al[16] have proposed that a limited knowledge of current perspectives on pain contributes to this attitude.

A broader understanding of the factors affecting pain and disability can provide the physical therapist with an additional conceptual framework for the evaluation and treatment of patients with LBP. We believe the application of this framework may improve the effectiveness of physical therapy interventions by helping the clinician identify those patients who are at risk for delayed functional recovery and who may benefit from additional non-impairment-based approaches.

A fundamental concept that relates to this framework is that in addition to the nociceptive response from injured tissues, a patient's perception of pain and behavioral response may be influenced by numerous biobehavioral factors. Biobehavioral factors can be described as a set of psychological, environmental, and psychophysiological processes that attenuate or exacerbate the discrepancy among pathology, pain, impairment, functional limitation, and disability.[17]

The purposes of this article are (1) to provide an operational definition of biobehavioral factors; (2) to review the role biobehavioral factors may play in the clinical presentation of LBP, functional limitation, and disability; (3) to identify commonly used approaches for their recognition and quantification; (4) to illustrate how an understanding of biobehavioral factors can assist the physical therapist in evaluation and treatment of patients with LBP; and (5) to identify certain gaps in current knowledge of the role of biobehavioral factors and their application in physical therapy.

Biobehavioral Factors Affecting Pain and Function

For the purposes of this article, we will use the definitions of impairment, functional limitation, and disability proposed by the National Center for Medical Rehabilitation Research.[18] Biobehavioral factors that relate to pain, functional limitation, and disability can be classified into three broad categories: cognitive-perceptual, environmental-behavioral, and psychophysiological. Biobehavioral factors are defined as a set of psychological, environmental, and psychophysiological processes that can attenuate or exacerbate the discrepancies among pathologies, reports of pain, and function.[17] Table 1 provides a list of these factors as they relate to LBP. The cognitive-perceptual dimension generally includes cognitive and perceptual factors that influence an individual's ability to effectively adapt to a personal challenge (eg, persistent or recurrent pain and loss of physical function). The environmental-behavioiral dimension includes characteristics outside the individual, such as the workplace, family, or social network, that serve to challenge or support the individual in his or her effort to effectively interact with the environment as well as behavioral responses to such factors. The psychophysiological dimension represents the response to external or internal stimuli in suspected peripheral and central biological mechanisms that modulate the pain experience. This biological response typically occurs in conjunction with an appraisal or cognitive evaluation of a given stimulus.

Cognitive-Perceptual Processes

Cognitive-perceptual processes are described as the mechanisms of thought and perception that influence a patient's interpretation of a stimulus or situation.[19] It is these processes that can help explain why one patient responds to pain in the lumbar region as "simply a sprain" while another is convinced it is a sign of a "disabling disease." Cognitive-perceptual processes relate to the thought processes and interpretation of stimuli that provide meaning or personal significance to bodily sensations, including pain. These thinking or cognitive appraisals and processes can exert an important effect on level of pain tolerance and function.[20,21]

A patient, for example, who experiences persistent pain despite multiple

attempts to find relief may legitimately interpret the pain as a sign of a "major" health problem. This phenomenon has been referred to as "disease conviction."[22] This phenomenon in turn can increase distress, which can affect pain by reducing the patient's ability to tolerate or adapt to the pain. Functional limitation may also occur in an effort to reduce the likelihood of increased pain. As the pain continues, a cognitive reappraisal may serve to further confirm that the pain is a signal of the existence of a major health problem, resulting in further distress.[23] Therefore, a patient who strongly believes that function cannot be restored until a cause for the pain is identified and eliminated, despite multiple previous unsuccessful attempts to do so, represents a major challenge to efforts directed at functional restoration. The cyclical nature of the process makes it very difficult for the clinician to intervene, particularly if the belief system is not identified and directly addressed.

A related phenomenon is the hypothesis that certain individuals may be predisposed to a cognitive-perceptual bias. This biasing can result in amplification of normal bodily sensations and misinterpretation of somatic symptoms associated with emotional arousal and distress as a confirmation of the presence of a significant illness. Another characteristic of this biasing is the interpretation of stressors in terms of physical (eg, symptoms) rather than emotional consequences.[24] This cognitive-perceptual bias, if present, may help explain why some patients display a heightened reactivity to pain and other bodily sensations. Such a process may also help explain the exaggerated" pain response that some patients exhibit when performing active range of motion of the trunk or their heightened response to gentle palpation of the low back.[24] In addition, these patients often report side effects from very low doses of antidepressant medication prescribed for pain and sleep disturbance that are not experienced by the majority of patients. Identification and management of factors such as anxiety and distress that may modulate this heightened sensitivity can assist the patient in shifting attention away from pain and other bodily sensations.

Perceived control over pain represents a cognitive factor that has been consistently associated with a range of positive outcomes.[26] Patients who believe they have some control over pain tend to report less pain and distress, and exhibit lower levels of disability.[27] In contrast, high levels of perceived disability are associated with actual increases in observed levels of disability.[28] The greater the level of perceived disability, the greater the impact on functional limitations. Thus, patients with LBP who believe that they are too disabled to perform various functional tasks may be more likely to demonstrate functional inabilities consistent with those beliefs, despite the fact that their impairments would not seem to preclude the performance of those specific functions.25 The perception of ability to function appears to be a better predictor of volitional performance (ie, the magnitude of observed function in response to a specific task) than actual impairment level in patients with chronic pain.[25] This frequently observed phenomenon illustrates the influence of cognitive processes on disability. The implication is that the health care provider must assess the level of disability, as preceived by the patient, in addition to impairment. If the level of perceived disability is high, assessment of factors contributing to this observation should be conducted. Although factors contributing to perceived disability have not been delineated, some of the common clinical phenomena related to perceived disability include level of distress (anxiety or depression), avoidance of negative consequences at work and at home, and fear of reinjury.[25]

Fear of pain represents another cognitive factor that can affect function.[29,30] For example, the fear of pain rather than the perception of pain can motivate certain types of behavior that avoid anticipated pain (eg, muscle guarding" . This phenomenon, although often observed by physical therapists, may be the consequence of a fear avoidance mechanism rather than the pain sensation, triggering a tendency to reduce or limit function. Identification of the cognitive, behavioral, and physiological components of this mechanism is useful in clinical management. Treatment efforts could then be targeted to address the component(s) of fear most evident (ie, thoughts, behaviors, physiological reactions).

The patient's perceptions of the workplace and family can influence the occurrence of acute LBP,[31] severity of experienced pain,[32] and work disability,[33] representing another cognitive factor that may influence treatment outcome. Research suggests that perceived problems at work (eg, work satisfaction, lack of supervisor support, work pressure, low levels of peer cohesion, physical comfort on the job, job clarity) can contribute to the development, exacerbation, and maintenance of LBP.

Another cognitive factor is perceived self-efficacy or the patient's belief in his or her ability to perform a certain set of behaviors, pain coping skills, or functional activities. Whether this is the inverse of perceived disability is unclear. Data exist, however, to suggest that self-efficacy expectations are predictive of behavior and attitude change[34] and as such represent cognitions that may play a role in facilitating outcome in physical therapy. Jensen et al,[35] for example, found consistent correlations between their judgments of patients' ability to use certain coping strategies (eg, aerobic exercise) and the patients' actual use of the strategies, To determine the likelihood that a certain behavior will occur (eg, practicing a set of stretching exercises each morning), a structured question inquiring about patients' judgment regarding their ability to perform such a behavior (ie, the target behavior) would be useful. A visual analogue scale methodology (eg, 0=not at all capable, 10=very capable) could be helpful for this purpose.

Environmental-Behavioral Factors

Environmental-behavioral factors are generally stimuli or events in the environment that facilitate an increase or decrease in a certain behavior, a behavior that in turn exerts an effect on the individual's environment. Variations in behavior are associated with a certain consequence, either negative or positive. In general, research in this area is directed at the instrumental role of behaviors related to pain and disability or the effect such behavior exerts on the patient's environment.[36] Although pain is a private and subjective experience (ie, no one can experience the pain of others), pain can be associated with a set of external observable behaviors that communicate to others that one is in pain. These verbal and nonverbal behaviors are referred to as pain behaviots.[37] Pain behaviors might include grimacing, verbal complaints of pain, amount of time spent lying down, and the use of supportive devices. Pain behaviors can be adaptive or maladaptive. Adaptive pain behaviors signal the need for assistance from others to facilitate the healing and recovery process. if the pain persists and recovery of function is delayed, a set of maladaptive pain behaviors may emerge. These pain behaviors are characterized by excessive dependency on family and health care providers, highly restricted function, and continuous verbal complaints of pain.36 These pain behaviors may serve to solicit responses from other individuals that actually delay recovery and foster a dependent state. Recognition of these maladaptive pain behaviors and the effects they may be exerting on pain and function can be helpful in facilitating recovery of function.

An example of these behaviors in the context of physical therapy is provided by the patient with nonspecific LBP who continuously exhibits a facial expression suggestive of heightened pain levels, despite persistent pain for 3 to 4 months, and continues to seek "passive treatments" for pain relief (eg, massage, ultrasound, moist heat). This patient may report less pain and "look better" immediately after these treatments. The passive short-term pain relief, however, may inadvertently be reinforcing the patient's dependence on physical therapy, preventing the self-directed functional recovery that is important for many patients. In such situations, the pain behaviors (eg, facial grimace, verbal complaints of pain) are reinforced by solicitous attention and temporary pain relief. Although such procedures may be appropriate for certain patients in the acute stage of injury recovery, the procedures may be quite detrimental to the long-term functional recovery in patients with recurrent or persistent pain and disability.[38] The physical therapist should be aware of the role such behavior can play in terms of obtaining social support, attention, or assistance for certain tasks or the avoidance of negative consequences such as pain, distress, or stressful interactions in the environment (eg, problematic supervisor, co-workers, or family members).

In addition to the psychosocial-envirodmental factors, there are a range of environmental factors of a physical nature, often referred to as ergonomic risk factors, that can contribute to the development, exacerbation, and maintenance of LBP.[39] A review of these factors is beyond the scope of this article. It is important, however, that clinicians be aware of the multivariate etiology of LBP[40] and not lose sight of the potential role ergonomic factors can play in delayed recovery of function.41

Pychophysiological Factors

Psychophysiological factors typically relate to an individual's physiological response to stressors, either external in terms of job or family stress or internal such as reaction to pain or some other aversive somatic stimuli.[17] Although research on psychophysiological factors in LBP has generated inconsistent findings,[42] limited evidence exists that certain patients with LBP demonstrate a heightened paraspinal electromyographic (EMG) response and/or delayed recovery of the EMG response following exposure to stressors that are personally relevant to them (ie, create difficulties in their lives). Perhaps of greater significance is the research on the modulating role of the sympathetic nervous system on pain.[17,43] Data indicate that the sympathetic nervous system is intricately involved in response to psychosocial stressors.[44] Heightened autonomic reaction to psychosocial stimuli or pain stimuli may contribute to a reduced ability to tolerate pain and subsequently lead to functional limitation and disability. Distress associated with perceived loss of control over the pain can also contribute to increased autonomic and musculoskeletal activity that may continue to cycle in a feedback loop, further maintaining pain and disability.[45]

Rationale for Biobehavioral Assessment in Clinical Practice

In addition to the cross-sectional and correlational studies supporting the role of various biobehavioral factors in LBP and associated disability, prospective clinical research on predictors of disability (eg, ability to work) and functional outcomes (eg, return to work) following multidisciplinary rehabilitation provides further support for the need to consider the role of these variables in assessment and treatment. Although work-related disability represents only one functional index of outcome, the studies summarized below relate to predicting this outcome as return to work is frequently viewed as a major treatment goal. The dichotomous nature of a return-to-work outcome (yes/no) also makes it relatively easy to measure and less controversial than other outcome measures. Clearly, there is a need for research on the impact of biobehavioral factors on other indexes of outcome.

In a limited number of prospective studies, predictors of prolonged work disability have been identified. Typically, a number of suspected predictors were assessed at the initial visit, with subsequent measurements obtained at 6-month, 1-year, and 2-year intervals. The most commonly assessed predictors included demographic data, job-related information, medical history, physical capacity assessment, and psychological measures. Although a detailed review of this research is beyond the scope of this article, the following is a brief outline of those variables reported to be predictive of work disability due to LBP. High levels of preocculation with somatic symptoms (eg, hypochondrias) as well as heightened reactivity to stress (hysteria) were described by Milhous et al[46] to be associated with work disability. Milhous et al also reported that psychiatric interviews that revealed high levels of distress, low levels of coping ability, low estimations of daily activity, and poor potential for vocational rehabilitation were also associated with work disability. Lacroix et al[47] reported similar findings and also identified a poor understanding of symptoms of LBP by the patient as an additional predictor. Lancourt and Kettelhut[48] reported that low scores on the Oswestry Low Back Pain Disability Questionnaire (eg, a high degree of perceived disability), unstable living arrangements, financial stress, and overall stress levels were predictive of work disability. Cats-Baril and Frymoyer,[49] in a frequently cited article, reported that measures of job dissatisfaction were associated with work disability.

In a study that investigated predictors of work disability in a public hospital outpatient clinic (in contrast to orthopedic clinics), Deyo and Diehl[50] found that among a subgroup of patients who were employed at the beginning of the study, the best predictor of whether they continued to work was a negative response to the question "Do you feel sick all the time?" The only predictor of final employment status was employment status at the time the study began. In a collateral study of indexes of distress ("behavioral signs" of abnormal illness behavior),[51] as measured by the Waddell Screen,[52] the investigators observed a reduction in behavioral signs in persons disabled with LBP (work disability=8.7 months) who successfully returned to work following a work-oriented physical rehabilitation program (no formal psychological intervention). At least one behavioral sign was present at discharge in 47% of the group that failed to return to work, in contrast to 12% of the group that returned to work. This study suggests the importance of early recognition and referral to an appropriate mental health care provider by the physical therapist for the patient with complex biobehavioral-related problems. This research also supports the conclusion that active physical rehabilitation may facilitate positive outcomes in the absence of direct psychological intervention in well selected patients.

Research is needed to identify whether a pattern of biobehavioral predictors of work disability and other outcomes exists. Such research can form the basis for assessment protocols that could assist in identifying persons who might benefit from more direct and aggressive psychological intervention in conjunction with physical therapy. The current literature on predictors is limited by the absence of standardized and valid measures of work disability; heterogeneous samples in terms of diagnoses, stages (acute, subacute, or chronic) and durations of the disorders, and clinical settings; and widely disparate variables used as predictors both within categories of measures (eg, biobehavioral, demographic, physical, workplace related) and across categories or domains of suspected predictors. Further research on predictors of work disability and other outcomes of interest following an index visit in both patients with acute LBP and patients with chronic LBP using standardized measures of predictors and outcomes should prove useful in further identifying the most critical biobehavioral factors. An integrated conceptual framework or model of work disability, for example, could be used for predictions and to choose measures for prediction of specific outcomes. We have developed one such model, which is described elsewhere.[53]

Another source of scientific data on the role of biobehavioral factors in pain and disability are studies identifying predictors of return to work following multidisciplinary rehabilitation for chronic back pain. Feuerstein et al[54] recently reviewed the outcome literature related to multidisciplinary rehabilitation efforts directed at facilitating return to work in patients who were work disabled because of chronic back pain. These authors identified five studies that predicted return-to-work outcome a minimum of 1 year following rehabilitation from measurements obtained before treatment. The authors categorized the predictor variables into five categories: medical history, demographics, physical findings, pain, and psychological indexes. Results from these studies indicated that the following psychological factors were predictive of return to work: low pain severity[55,56] and pain drawing scores,[55] high levels of satisfaction with treatment,[57] high cooperativeness during treatment,[55] low levels of hypochondriasis,[55] distrust and stubbornness,[55] depression,[55] and "premorbid pessimism."[55] Although the relative predictive strength of each of these variables cannot be determined at present, these findings indicate the importance of a range of biobehavioral factors as prospective predictors of outcome.

Lastly, two recent studies, one in a primary care setting[58] and one conducted in an aircraft manufacturing plant in Quebec, Canada,[59] provide further support for biobehavioral factors as predictors of outcome. The role of perceived disability as a predictor of poor" clinical outcome (high patient ratings of pain-related disability) or occurrence of total work disability and workers' compensation related to back problems during the following year is apparent in the results. VonKorff et al[58] observed that predictors of poor functional outcome or continued high levels of pain in primary care (not all workers' compensation cases) were high levels of reported disability due to pain, days in pain, low educational attainment, and female gender in contrast to recency of onset of pain (acute versus chronic). These researchers also observed that high levels of depression were associated with poor outcome and that marked reductions in depressive symptoms from baseline to 1-year follow-up were associated with "good-fair" outcomes. Perceived limitation in performing work or in performing activities of daily living (as measured by the Oswestry Low Back Pain Disability Questionnaire) and history of compensation (ever) were the three independent predictors of compensation or work disability at 12 months due to LBP in the investigation of aircraft assembly workers,

Given the potential of biobehavioral factors to affect outcomes, physical therapists should be aware of strategies for detecting these factors. Although there is little doubt that most physical therapists can recognize overt signs such as heightened reactivity to pain, pain behavior, and global distress, the determination of those circumstances in which it may be most advantageous to pursue more subtle identification and quantification of biobehavioral factors can be more problematic.

When biobehavioral factors are of sufficient intensity and duration, referral to an appropriate mental health service provider (clinical psychologist, psychiatrist, social worker) is indicated. Physical therapists should recognize that there are behavioral medicine clinicians with expertise in addressing the biobehavioral factors affecting pain, distress, and disability.[60-62] These providers should be identified in order to develop collaborative interactions in relation to specific patients. These practitioners generally take a time-limited, specific goal-oriented approach to treatment. They can serve as a useful source of input as to whether a given patient may be appropriate for referral. As a general guideline, when a patient's compliance problems are recurrent, pain levels continuously interfere with functional improvement, and distress is at a level at which problems in the individual's life predominate discussions in treatment or interfere with the ability to progress through a series of protocols, despite multiple attempts to acknowledge and work with these problems, a referral should be initiated.

Commonly Used Assessment Approaches

Although research has indicated a comorbidity of various types of psychopathology and LBP in subsets of patients,[63-65] this review does not address psychopathology. Also, although high levels of emotional distress (anxiety and depression) as measured by standardized psychological assessment devices could be considered in a discussion of biobehavioral factors contributing to prolonged pain and disability, these are not reviewed. The rationale for this is based on the following: (1) The intent of this article is to highlight certain areas potentially affecting physical therapy outcome that the physical therapist can address independently or with consultation; (2) the conceptual approach used in this article differs from classic models of psychopathology; and (3) methods such as structured diagnostic interviews and standard psychological testing used to assess psychopathology and distress are not within the scope of practice of the physical therapist and therefore an extensive review, although of some interest, was not included, particularly given the primary focus of the article. The interested reader is referred to other resources related to these areas.[66-68]

Several approaches have been developed for the assessment of cognitive-perceptual, environmental-behavioral, and psychophysiological factors affecting pain, functional limitation, and disability.[69] The various assessment procedures discussed provide a set of measures that have demonstrated validity, reliability, and relative ease of application in a clinical setting. Research on the validity and reliability of these measures continues. New biobehavioral factors may also be identified that are more directly related to pain, functional limitation, and disability. Assessment tools based on this research may provide more helpful approaches to the physical therapist in the future. Although this section provides an overview of various assessment procedures, the wide-scale use of these approaches in physical therapy practice must await further validation of their clinical utility with a range of patient populations and settings. When possible, we will indicate which measures have been more widely used and validated.

Structured Biobehavioral Interview

The assessment process should first include a brief structured interview. This interview is typically followed by the use of questionnaires to provide a more detailed analysis of suspected biobehavioral factors. The interview should follow a set of clinical hypotheses related to the suspected involvement of the three broad biobehavioral dimensions.[70] A summary of the components of such an interview is provided in the Appendix.

The interview should take a directive approach, probing for information that identifies signs and symptoms of distress associated with pain. Examples of these signs and symptoms are sleep disturbance, high levels of anxiety, fear, anger, depressed mood, inactivity, medication overuse, and reactions of others (eg, family members) to overt demonstrations of pain. Information on the patient's reactions to stressors both prior to the onset of symptoms and at the present time is also helpful. Such information can provide a better sense of the patient's overall coping resources, Questions about financial aspects of the problem, such as litigation, are important, but it should be emphasized that financial incentives are not necessarily the exclusive cause of delayed recovery. Identification of a patient's expectations for treatment are also helpful to provide a perspective as to what the patient is expecting from treatment (eg, pain elimination versus pain relief, increased strength and flexibility, learning to cope with pain). With directive questioning, the clinician should obtain sufficient information to refine a set of hypotheses regarding the role of biobehavioral factors in pain and function within a 15- to 20-minute period. It is important to realize this interview should be viewed as a screen, not as an opportunity to obtain a detailed psychological assessment of factors affecting pain and disability.

Cognitive-Perceptual Measures

The instruments available to measure cognitive-perceptual factors can be organized into the following categories: pain experience, beliefs regarding pain and treatment, perceptions of work and family environments, cognitive coping style, fear of pain, perceived self-efficacy regarding function, and pain coping. Table 2 provides a list of assessment procedures available. The majority of these measures are included in the references or available in Turk and Meizack.[69]

Pain experience. The pain experience is more than a simple sensory-based response to nociceptive input from an injured site. This multidimensional concept of pain is applicable to acute, recurrent, and chronic LBP. Melzack and Wall,[71] in the development of the Gate Control Theory of pain, divided the pain experience into sensory, affective (emotional), and cognitive (meaning) components. The McGill Pain Questionnaire (MPQ)[72] provides a measure of these components through the use of pain descriptors (eg, "stabbing," "pounding," "tugging," "tiring," "sickening," "distressing"). Although the MPQ can also serve as an overall measure of pain severity (MPQ total score), its clinical utility is the ability of the scale to identify whether a patient tends to use sensory, affective, or cognitive labels to describe the pain experience. Although the relative independence of the three factors or dimensions have been questioned,[73] the pattern of this description (relative emphasis on a given dimension) can provide clinical insight into the degree of suffering or extent of affect or distress associated with the pain. For example, the sensory component of pain is described with such terms as "throbbing," shooting," and "stabbing," whereas examples of language used to describe the affective dimension of pain are tiring ... .. sickening," and "grueling." For a detailed review of recent research on the MPQ, refer to Melzack and Katz.[73] Pain experience can also be measured through the use of pain or body charts. The manner in which a patient completes these standard anatomic figures can also reveal the extent of distress associated with pain.[74,75]

Beliefs regarding pain and treatment. The Pain information and Beliefs Questionnaire[76,77] and the Survey of Pain Attitudes[78] represent two scales that assess these beliefs. When the belief system of the patient is inconsistent with the treatment rationale and plan of the therapist, compliance problems may emerge. Therefore, it can be helpful to identify those beliefs and work with the patient to jointly develop a treatment plan that is consistent with his or her beliefs. Such information can also serve as a useful guide for determining the need for patient education, although it should be emphasized that in certain patients with strong belief systems, education alone will not modify the belief structure and more extensive cognitive therapy may be required.[79] This phenomenon is particularly evident in patients who have a tendency to view pain and their illness as encompassing all aspects of their lives.[80] The use of cognitive distortions or errors may characterize their thinking patterns.[81] Another possibility is that a strong disease conviction and persistent search for "a cause and a cure" may represent a coping mechanism for handling uncontrollable stress.[80] These individuals are often preoccupied with bodily symptoms, tend to reject medical opinion, particularly if it is not consistent with their concept of their problem, and continue to search for the "correct" diagnosis and treatment. This search may represent a means of attempting to manage a dimension of their problem (choice of provider and treatment) that appears to be under their control. Scales to measure such belief systems that may negatively affect treatment outcome are the Cognitive Error Questionnaire[78] and the Illness Behavior Questionnaire.[22]

Perceptions of work and family. Perceptions of the work environment represent another cognitive factor with important potential clinical implications. The presence of perceived workplace problems can impede rehabilitation efforts directed at functional restoration and return to work. There are two measures that the physical therapist might want to consider. One is the Work APGAR.[31] This brief scale (7 items) measures work satisfaction (eg, co-worker support, enjoyment of job tasks, relationship with supervisor). Another measure that is based on a broader conceptualization of the dimensions of the work environment is the Work Environment Scale.[82] This 90-item test consists of 10 subscales that assess the relationship (involvement, peer cohesion, and supervisor support subscales), personal growth (autonomy, task orientation, and work pressure subscales), and system maintenance and change (clarity, control, innovation, and physical comfort subscales) dimensions of a work environment. Evidence of low levels of physical comfort, minimal supervisor support, and high work pressure may trigger the need to conduct an ergonomic job analysis in a given patient. Many other scales are also available for assessing various aspects of the work environment, job dissatisfaction, and job stress.[83]

Perception of the family environment has also been related to pain.32 A 90-item questionnaire used to measure patients' perceptions of their family environment is the Family Environment Scale.[84] This scale measures 10 dimensions of family environment, including cohesion, expressiveness, conflict, independence, achievement orientation, intellectual-cultural orientation, moral-religious orientation, organization, and control. Increased family conflict and independence have been associated with higher levels of pain.[32]

Coping. The assessment of how a patient copes with pain and functional limitation represents another important cognitive area. Scales to assess coping processes affecting pain and functional abilities include the Pain Cognitions Questionnaire,[85] the Coping Strategies Questionnaire,[86] and the Vanderbilt Pain Management Inventory.[87] The specific dimensions these scales measure are listed in Table 2. In general, these scales are helpful for identifying whether the patient tends to take an active or passive approach to coping with pain (active approaches associated with more positive outcome, pain reduction, functional improvement) and for identifying the type(s) of coping strategies a patient uses for pain management.

Perceptions of function and disability. Although the evaluation of the patient with LBP often includes an assessment of strength, flexibility, and lifting capacity,[56] the assessment of the patient's perception of his or her functional abilities also represents a useful source of information. This is particularly noteworthy when a discrepancy exists between observed and perceived functional abilities. When such discrepancies are evident, it is important to pay particular attention to factors that might help explain such a clinical situation. A patient's level of distress (anxiety, depression, anger), factors in the environment such as poor supervisor relations at work, or cognitive-behavioral mediators of disability (eg, strong disease conviction that limits efforts at physical restoration until the cause for pain is identified and a "cure" is found) may be operational. Disability questionnaires are a helpful first step in identifying the presence and level of perceived disability.

There are several questionnaires that can be used to measure perceived disability. Mulard[88] provides a review of the background, psychometrics, and implementation of 14 commonly used measures. (The various scales are not included in Tab. 2. The reader is referred to Millard.[88]) A potentially useful brief scale that emerges from the review is the Functional Assessment Screening Questionnaire.[89] This measure requests the patient to rate level of difficulty for 15 specific behaviors and functional activities (eg, grocery shopping, cutting toenails) along a five-point scale. The instrument provides an index of function that is only minimally related to psychological variables.[90] Although additional research is needed to determine the robustness of the scale's minimal psychological influence, it appears to provide a relatively psychological "bias-free" index of self-reported abilities. Another instrument for assessing perceived disability that is not a self-report survey questionnaire but rather an index derived from a clinical interview is the Waddell index.[91] This index assesses the patient's reported ability to bend, lift, sit, stand, walk, drive a car, engage in social activities, sleep, engage in sexual activity, and dress. The index has been related to independent measures of trunk strength and flexibility[28] and clinical outcome for patients with chronic LBP.[25]

Fear of pain. Fear of pain represents another cognitive factor that may affect functional ability. The Pain Anxiety Symptoms Scale is a self-report index of the fear of pain that assesses cognitive, behavioral, and physiological components of pain-specific fear.[30] The scale is brief (53 items) and is divided into four subscales: somatic anxiety (eg, "become sweaty when in pain"), cognitive anxiety (eg, "worry when I am in pain"), fear (eg, "dread feeling pain"), and escape-avoidance (eg, "when in pain, stay as still as possible").

Waddell and colleagues[92] have also developed a fear-of-pain measure. This scale assesses a patient's beliefs and his or her concerns and fears about pain and work (eg, my work might harm my back) and pain and physical activity (eg, physical activity makes my pain worse) that might contribute to avoidance of such activities. The Fear-Avoidance Beliefs Questionnaire was demonstrated to be the most specific and strongest predictor of work loss due to LBP.[92] Papciak and Feuerstein[93,94] have also demonstrated that simple visual analogue scales of fear of pain and reinjury are associated with increased distress and lower expectations regarding function.

Self-Efficacy. Another cognitive factor is self-efficacy or the patient's assessment of his or her expected ability to perform a behavior or coping skills necessary to influence function or pain (ie, self-efficacy beliefs). These expectations affect pain and function in patients with persistent LBP.[19,20,93] Therefore, questions regarding self-efficacy (ie, self-appraisal of potential ability) related to the actions necessary to achieve desired changes in behavior (function), cognitions (thoughts), and emotions (moods) during the initial evaluation can provide valuable information. When return to work is a desired outcome, the use of work reentry expectation measures can be helpful. There are four visual analogue scales we use in clinical practice that have been related to measures of lumbar peak torque and range of motion in LBP during an initial evaluation[94] and return to work following rehabilitation.[95]

Assessment of self-efficacy expectations may aid in determining how much effort will be needed to assist the patient in achieving attitudinal and behavioral changes needed to attain a positive clinical outcome. in general, the lower the self-efficacy expectation, the less likely the desired outcome, unless a direct intervention is initiated to assist the patient in modifying the barriers to change.[35] Examples of self-efficacy questions regarding ability to exercise for patients with LBP are provided by Dolce and colleagues,[20,21] questions regarding coping with pain were published by Jensen et al,[35] and items related to return-to-work expectations were presented by Papciak and Feuerstein.[93] A standardized scale that was developed for patients with arthritis provides an example of a scale with predictive validity.[96] Currently, there are no similar scales for LBP reported in the literature.

Environmental-Behavioral Measures

The assessment of pain behaviors has been described in detail.[26] Numerous methods are available that provide indices of the frequency and severity of pain behavior as well as the measurement of responses to this pain behavior by health care providers and the patient's family members.[26] For the purposes of this discussion, the physical therapist may find the Pain Behavior Scale, a brief behavioral observation and self-report measure first developed for inpatient use[97] and subsequently modified for outpatient use by Feuerstein et al,[98] of interest. The Pain Behavior Scale (outpatient version) consists of a series of target pain "behaviors," including vocal complaints (verbal and nonverbal), facial grimaces, awkward standing postures, body language, and stationary movement. There are also self-reported measures of medication use and time spent lying down per day (8 AM-8 PM) due to pain (downtime). The patient is instructed to sit, stand, walk 10 steps, and sit while the observer rates a number of pain behaviors on a three-point scale (none, occasional, frequent). The patient is asked for responses to the medication and downtime items. The assessment requires 5 minutes to complete.

When pain behaviors are present, the physical therapist may also be interested in identifying potential factors that contribute to the exacerbation or maintenance of such behaviors. The Multidimensional Pain Inventory (MPI) can be helpful in identifying the role of support and concern from others (negative, solicitous, distracting responses) on pain behavior.[99] The full 52-item 12-scale inventory is divided into three parts: (1) dimensions of chronic pain experience, (2) a patient's perceptions of responses of others to his or her pain, and (3) a patient's report of common daily activities. The scale is relatively brief, is easy to score, and has demonstrated reliability. Of particular interest are the findings that indicate the predictive validity of the "responses of others" section. Measures of these indexes were associated with the maintenance of pain and disability.[100] Thus, the combination of the Pain Behavior Scale and the MPI can provide clinically useful measures of the presence of observable pain behaviors and identification of factors potentially contributing to and maintaining such behaviors.

Although measures of a person's social environment such as job- and family-related stressors can be conceptualized under behavioral-environmental factors, these indexes were included in the cognitive-perceptual factors sections because of the importance of the individual's self-appraisal of these environmental stimuli in contrast to the actual quantitative measurement of exposure. Stress models and supportive research emphasize the role of the appraisal process of a potential threatening situation in contrast to the external stressor itself[44] and are therefore included in the section on cognitive-perceptual factors.

In contrast, exposure to physical stressors in one's environment can more directly influence levels of fatigue, pain, and disability. Various methods for ergonomic job analysis and self-report questionnaires of exposure are available. Review of these approaches is beyond the scope of this article. The interested reader should refer to Ulin and Armstrong[101] and Keyserling et al.[102]

Psychophysiological Measures

The evaluation of the psychophysiological dimension typically involves a systematic assessment of prestress baseline, reactivity to stress, and recovery of selected physiological variables assumed to contribute to the exacerbation or maintenance of the disorder. A number of techniques that have been developed for the evaluation of anxiety states[103] have been adapted for the measurement of various pain disorders.[104] Typically, the measures include surface EMG recorded from muscles assumed to be at high tonic levels or highly reactive to psychosocial stressors or pain. Skin conductance is also a frequently measured autonomic response, given its direct relationship to systemic activity in the sympathetic nervous system. The protocols typically involve collecting baseline indexes of the measures of interest (eg, paraspinal, surface EMG), followed by the presentation of a stressor (eg, arguing with a supervisor), to determine reactivity in target measures as well as the length of time required for the measure to return to baseline indexes. Although the indications for such testing remain unclear, the approach can assist in determining whether the patient is demonstrating heightened musculoskeletal or autonomic reactivity to psychosocial stressors as well as the association of such activity to increases in pain levels.[104] This evaluation process can help identify the potential utility of a psychophysiological intervention such as relaxation or biofeedback training. Other methods investigating left and right paraspinal patterns of EMG activity have also been used.[105] Descriptions of the instrumentation and methodologies can be found elsewhere.[104]

An indirect approach to measuring suspected musculoskeletal and autonomic reactivity is the use of self-report indexes. One such measure is the Modified Somatic Perception Questionnaire (MSPQ).[106] This scale assesses the extent to which the patient reports experiencing symptoms characteristic of either musculoskeletal (eg, muscle twitching or jumping, tense feeling across forehead) or autonomic activity (eg, nausea, sweating all over, heart rate increase). Although high scores on this measure are related to increased global distress,[25] the scale appears to provide a useful self-report index of musculoskeletal and autonomic reactivity. The scale's use, however, as a predictor of self-reported functional outcome (ie, perceived disability) is questionable.[50]

Choice of Assessment Devices

When considering the use of any questionnaire, one should define the hypotheses to be tested and use a questionnaire that best addresses these hypotheses. For example, if a therapist suspects that a patient has cognitive distortion and a high perceived level of disability associated with a very negative belief system regarding pain and that this combination of factors appears to be contributing to a prolonged delay in functional recovery, measurement of perceived disability and cognitive distortion might be undertaken to document the presence of both. The choice of the brief Functional Assessment Screening Questionnaire[90] and the Cognitive Error Questionnaire[81] might prove useful for documenting the extent of perceived disability and the type of cognitive distortions that are present (eg, catastrophizing, overgeneralization, personalization, selective abstraction). Such information would provide a better clinical appraisal of how the patient is thinking in relation to physical function and what thought processes he or she uses to draw conclusions regarding functional abilities. If catastrophizing, for example, is a patient's predominant cognitive style, the patient may perceive any attempt to improve functional ability as futile. An example of such a negative cognitive view of pain and function might be phrased as follows, "After all, I can't do anything without my pain getting worse!" An individual with this cognitive set (pattern) may benefit from the achievement of frequent short-term goals such as adding one repetition to an exercise each day and consistently pointing out the incremental progress.[107]

Another example of the potential utility of approaching a clinical problem from a biobehavioral perspective would occur when a distressed patient describes a nonconventional distribution of pain. In this case, the use of a "pain map" to identify distribution and the MPQ to assess the use of terms that reflect sensory, affective, and cognitive dimensions of the pain experience might provide a better sense of the role of distress on pain distribution.[74] If there is a question as to whether solicitous responses from others or a significant degree of marital discord may be contributing to this distress and pain, the MPI[99] may also be of use. If it is determined that the distress, pain, and delayed recovery appear to be affected by a high degree of marital distress, a consultation with a psychologist who evaluates and treats patients with persistent pain might be justified in efforts to facilitate recovery. Although a focus on restoration of function through therapeutic exercise and instruction in personal and workplace ergonomics may improve strength, flexibility, endurance, and safety, if the distress level is sufficiently high to interfere with the physical therapy plan and the source of the distress is not addressed directly, full functional recovery may not be achieved. Such an outcome may be averted by considering the approach to be presented or a referral for more extensive evaluation and treatment of biobehavioral factors.

Another approach frequently used in clinical settings is to compile a set of measures that assess key areas assumed to affect outcome (eg, distress, pain behavior, fear of reinjury, expectation regarding function). These measures can be used as a screening device for all patients with LBP. Patients could complete the screen while in the waiting room prior to the initial physical therapy evaluation.

Discussion

Physical therapists play an active and strategic role in the management of LBP and are in a position to assist in the prevention of prolonged pain and disability. If biobehavioral factors play a role in the etiology, exacerbation, maintenance, and disability of LBP, recognition of these factors by physical therapists and efforts to reduce their impact early in the health care delivery process could potentially reduce the long-term burden of these disorders. For patients who currently experience recurrent or persistent pain and disability, and who have not responded to physical therapy intervention, applying the approach presented in this article may assist additional treatment efforts and facilitate improved outcomes in selected patients. Although the potential synergy of a biobehavioral approach with physical therapy appears limitless in terms of benefits to our patients, only sound scientific research can determine its ultimate utility.

Although support for the role of biobehavioral factors exists, there are numerous unanswered questions. Further research relating to measurement, mechanisms of action, assessment, and treatment in the context of physical therapy for LBP is warranted. in terms of measurement, further determination of the reliability and validity of various scales for different subgroups of patients with LBP would assist in identifying the most robust measures. Research that investigates the interaction among biobehavioral factors; the natural history of LBP; and the clinical dimensions of LBP in terms of impairment, functional limitations, and disability should assist in further delineation of the specific contribution of each of these factors to the etiology, exacerbation, and maintenance of LBP.

In addition to the basic research questions related to the validity of these measures, a number of practical questions need to be addressed. What are the indications for screening for biobehavioral factors? What requisite skills are needed for assessment? Will patients comply with such an assessment, and what effect will this compliance have on the traditional patient-physical therapist interaction?

Another important question is: To what degree do the subsets of patients with biobehavioral factors respond differentiary to a given treatment in terms of pain; compliance; and changes in impairment, functional limitation, and disability? Whether early identification of patients with biobehavioral factors followed by specific interventions to address these factors enhances outcomes relative to usual care is not yet known.

Biobehavioral factors are often erroneously equated with the term "malingering." These unexplained physical symptoms or reactions to persistent pain may represent a normal coping response to a chronic stressor(s).[108,109] The presence of malingering is a judgment made by the examiner that infers the patient is making a conscious effort to falsify the nature of his or her problem. in the psychiatric literature, the diagnosis of "malingering" has generally been replaced by the "factitious disorder," which is similarly highly judgmental.[66] Such a diagnosis can create substantial detrimental effects on the patient.[110] Terms such as "malingering" or "symptom magnifier" do not provide the clinician with a means for addressing factors that may serve to contribute to delayed recovery. Labels such as "malingering" have very little clinical utility in efforts directed toward functional restoration. A potentially more productive approach to the complex problem of pain-related disability may be to identify specific factors that are inhibiting functional recovery in these patients and to target interventions directed at modifying such factors.

Conclusion

Low back pain continues to represent a major challenge to health care providers, including the physical therapist. Its prevalence, multivariate etiology, highly recurrent nature, and resistance in chronic cases suggest that a simple clinical solution is unlikely. We suggest that the biobehavioral approach presented in this clinical perspective will assist physical therapists confronted with patients with complex problems to consider a new way of conceptualizing and managing such a clinical situation.

Acknowledgments

We appreciate the helpful review of this manuscript by Bruce A Barton, MD, Susanne Callan-Harris, PT, Thomas R Zastowny, PhD, and Jeffrey M Lackner, PsyD. We also acknowledge manuscript preparation by Jennifer Boehles.

Appendix. Structured Pain Interview(a)

I. Description of demographics, referral source, diagnosis II. Description of pain (repeat for multiple problems)

A. Areas of pain

B. Pain intensity and descriptors

C. When did it start?

D. Precipitating event(s)

E. Frequency/duration

F. Pattern (over months, years) III. Treatment-induced changes in pain

A. Medications

B. Surgeries

C. Other treatments (eg, chiropractic, acupuncture)

D. What does patient do to decrease pain?

E. What does patient do that increases pain? IV. Brief description of additional medical problems V. Life changes due to pain

A. What changes in activity have been necessary because of pain?

1. Percentage change (+ or -); get before and after frequencies

2. Include

a. Downtime

b. Recreational (fun) activities

c. Social activities

d. Sex assess sexual dysfunction as necessary)

e. Use of intoxicants

f. Family responsibilities

g. Other activities that have changed

B. How does patient respond to others when pain is at its worst? Explore in detail for operant factors.

C. How do others respond to patient when patient shows he or she is in pain? Explore in detail

for operant factors.

D. Psychological changes due to pain (specify time course and current coping strategies)

1. Anxiety

a. Muscle tension

b. Autonomic distress

c. Worry or feelings of insecurity

2. Depression

a. Appetite

b. Sleep

c. Suicidal ideation/intent/attempts (including history)

d. Feelings of loss/self-blame

e. Past history (patient/family)

f. Loss of interest in enjoyable activities

g. Loss of energy

3. Anger/irritability

E. Premorbid adjustment

1. Work

a. Stability (rate of change in jobs, periods of unemployment, and reasons)

b. Perceived job performance

c. Satisfaction

d. Changes in work situation coincident with accident illness

2. Family

a. Stability

b. Satisfaction

3. Heterosexual or marital relationship 

a. Stability

b. Satisfaction

4. Mood

a. Description (note key terms)

b. Prior psychologic treatment (dates? for what problem?)

c. Family history of emotional/mental disorder or psychologic treatment VI. General financial aspects

A. Current income/past income

B. Does change in income present a problem?

C. Assess level of financial security--future

D. Litigation--purpose?

* Recovery of medical bills

* Salary

* Lump-sum settlement 

* Pain and suffering

E. Spouse working due to patient's unemployment? VII. Goals, plans, outlook

A. What does patient desire from treatment?

B. What does patient desire if primary goal cannot be met? (a) Reprinted with permission from Feuerstein & Dobkin.(70)

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M Feuerstein, PhD, is Professor, Departments of Medical and Clinical Psychology and Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, Bethesda, Md 20814. Address all correspondence to Dr Feuerstein at the Department of Medical and Clinical Psychology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd, Bethesda, MD 20814-4799 (USA).

P Beattie, Phd, PT, OCS, is Assistant Professor, Department of Physical Therapy, Ithaca College, 300 E River Rd, Suite 1-102, Rochester, NY 14623, and Center for Occupational Rehabilitation, University of Rochester Medical Center.

The completion of this article was supported in part by Grant No. H133A00040, "Cost-Benefit Analysis of Multidisciplinary Work Conditioning in Chronic Low Back Pain Rehabilitation," from the National Institute on Disability and Rehabilitation Research to Dr Feuerstein.

The opinions or assertions contained herein are the private ones of the authors and are not to be construed as official or reflecting the views of the US Department of Defense or the Uniformed Services University of the Health Sciences.

This article was submined January 7, 1994, and was accepted December 5, 1994.