Beyond pain

Clinical Psychology Review, Vol. 19, No. 1, pp. 97–119, 1999Copyright © 1999 Elsevier Science LtdPrinted in the USA. All rights reserved

0272-7358/99/$–see front matter

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97

BEYOND PAIN: THE ROLE OF FEAR AND AVOIDANCE IN CHRONICITY

Gordon J. G. Asmundson

Clinical Research and Development Program, Regina Health District and University of Regina

Peter J. Norton

Clinical Research and Development Program, Regina Health District

G. Ron Norton

University of Winnipeg

ABSTRACT.

The purpose of the present article is to provide unification to a number of some-what disparate themes in the chronic pain and phobia literature. First, we present a summary re-view of the early writings and current theoretical perspectives regarding the role of avoidance inthe maintenance of chronic pain. Second, we present an integrative review of recent empirical in-vestigations of fear and avoidance in patients with chronic musculoskeletal pain, relating thefindings to existing cognitive-behavioral theoretical positions. We also discuss several new andemerging lines of investigation, specifically related to information processing and anxiety sensi-tivity, which appear to be closely linked to pain-related avoidance behavior. Finally, we discussthe implications of the recent empirical findings for the assessment and treatment of individualswho experience disabling chronic musculoskeletal pain and suggest possible avenues for futureinvestigation. © 1999 Elsevier Science Ltd

THERE IS growing evidence that some, but not all, people with chronic musculoskel-etal pain avoid a wide variety of stimuli, including those directly (e.g., physical activities)and indirectly (e.g., social activities) associated with pain. This avoidance behavior isoften associated with poorer treatment performance; however, the psychological fac-

Correspondence should be addressed to Gordon J. G. Asmundson, Regina Health District, Clin-ical Research and Development Program, 2180 23rd Avenue, Regina, Saskatchewan S4S 0A5,Canada. E-mail: [email protected]

98 G. J. G. Asmundson, P. J. Norton, and G. R. Norton

tors influencing avoidance behaviors are not well understood. In this article we will(a) review the existing literature on pain and avoidance, (b) highlight current re-search suggesting that information processing biases and anxiety sensitivity, a disposi-tional trait believed to amplify fear reactions (Reiss, 1987, 1991; Reiss & McNally,1985), may be closely linked to pain-related avoidance behaviors, (c) suggest how thisinformation might contribute to assessment and treatment strategies for patients withchronic musculoskeletal pain, and (d) offer suggestions for future research.

GENERAL BACKGROUND

Pain has traditionally been explained by the medical model of disease and, as such,was viewed as a pure sensory experience arising from noxious stimulation (e.g., physi-cal injury or other pathology). The past three decades, however, have seen the rise ofa number of alternative models that incorporate psychological (e.g., perception, cog-nition, affect) and behavioral (e.g., avoidance) factors to explain the pain experience(Fordyce, 1976; Melzack & Casey, 1968; Melzack & Wall, 1982; Turk, Rudy, & Boucek,1993). These models have led to considerable increases in our understanding of painand pain behaviors (for recent reviews, see Gamsa, 1994a, 1994b).

Today, pain is typically conceptualized as a complex, subjective, perceptual phe-nomenon that involves a number of dimensions, including, but not necessarily lim-ited to, intensity, quality, time course and personal meaning (also see Merskey &Bogduk, 1994). For most, pain initiates short-term adaptive processes that facilitatethe ability to identify, respond to, and resolve physical injury. However, for approxi-mately 10% of adults who sustain musculoskeletal injury, the experience of pain per-sists long after any identifiable organic pathology has healed (Waddell, 1987). Pain ofthis nature, and preoccupation therewith, often leads to significant distress, suffering,and functional disability (for review see Waddell, 1992) and has been associated withinappropriate use of medical services and high cost insurance claims (Nachemson,1992; Spengler, Bigos, & Martin, 1986). Consequently, researchers and clinicians havefocused considerable attention toward gaining a better understanding of the psycho-logical processes by which pain becomes persistent.

Over the past decade, there have been numerous investigations of cognitive and af-fective aspects of the pain experience. One need only scan recent reviews (e.g., Craig,1994; Weinsenberg, 1994) to gain an appreciation of the effort that has been put to-ward evaluating the role of emotional distress, catastrophizing, coping strategies, self-efficacy, and motivational factors in persistent pain. Below we will review, discuss, andelaborate upon an avenue of investigation that has been receiving increased attentionover the past few years—the interface between chronic musculoskeletal pain, fear,and avoidance behavior.

AVOIDANCE BEHAVIOR AND PAIN

In this section we define avoidance and present behavioral and cognitive-behavioralmodels that have been proposed to explain avoidance behavior in patients withchronic pain. As well, we summarize and critique the empirical literature pertainingto these models.

Chronic Pain and Avoidance 99

Avoidance

Avoidance refers to a pattern of behavior that delays, or puts off, an undesirable situa-tion or experience. In addition, avoidance behavior has long been recognized as aspontaneous and adaptive response to acute injury (Wall, 1978). To illustrate, an indi-vidual who has pulled a muscle in their lower back may reduce (or avoid) physical ac-tivity in the days immediately following the injury, perhaps by resting or through theuse of supportive devices, in order to avert pain sensations which, in turn, allows forthe healing of the damaged tissue. If, however, avoidance behavior persists after in-jured tissue has healed, then avoidance may be viewed as a maladaptive response thatmay contribute to disability (e.g., the “disuse” syndrome; Bortz, 1984), physical decon-ditioning, dysphoric affect, and preoccupation with somatic symptoms (including per-sistent complaints of pain). Several avoidance-based models (discussed below) havebeen proposed on the basic premise that avoidance of the pain experience and pain-ful activities leads to perpetuation of pain and related behaviors (e.g., disuse, disabil-ity, and avoidance itself). Similar models of avoidance behavior have been associatedwith phobic states (Marks, 1969) and anxiety disorders (Barlow, 1988).

Avoidance Learning

The early writings of Fordyce (1976; Fordyce, Shelton, & Dundore, 1982) describehow behaviors associated with persistent pain arise as a product of operant condition-ing. Specifically, individuals learn that avoidance of situations and activities in whichthey have experienced acute episodes of pain will reduce the likelihood of re-experi-encing pain. The avoidance behavior is reinforced, in the short-term, through the re-duction of suffering associated with nocioception and, as stated above, can be anadaptive response. Limitations in activity over time, however, become maladaptive asreinforcement of the avoidance behaviors shifts from reduction of the nocioceptiveinput itself, to various other positive and negative reinforcers. For example, pain be-havior may persist because it allows one permission to avoid attending to aversive re-sponsibilities. Likewise, investigators have recently suggested that pain behavior maypersist as a result of social rewards (e.g., reduced social anxiety resulting from re-duced social responsibility; Asmundson, Norton, & Jacobson, 1996), and the reduc-tion of anxiety associated with the anticipation of further aversive pain-related experi-ences (McCracken, Zayfert, & Gross, 1993).

Cognitive-Behavioral Perspectives

Philips (1987) has also argued that avoidance behavior is a major contributor to chronicpain. Indeed, she states

“that avoiding is the most prominent component of pain behavior”

(Philips, 1987; p. 274, emphasis in original). Her model, however, diverges from thatof Fordyce in that it incorporates postulates of the cognitive theory of avoidance (Se-ligman & Johnson, 1973) to account for cases in which behavioral withdrawal contin-ues in the absence of adequate reinforcement. Specifically, she posits that avoidance isdetermined by a species-specific preference for minimizing discomfort and pain, plusthoughts and beliefs (comprising expectancies, feelings of self-efficacy, and memoriesof past exposures) that re-exposure to certain experiences or activities will produce bothpain and suffering (see Figure 1). These thoughts and beliefs are reinforced by theavoidance behavior itself. Thus, once initiated, avoidance leads to decreased self-efficacy


and increased expectations that stimulation will increase pain that, in turn, leads to in-creased avoidance. In essence, then, and akin to common notions of chronic fear andanxiety, chronic pain and avoidance behavior are conceptualized as a self-defeatingcycle between cognition and behavior. As such, the model emphasizes and allows fordetailed examination of the contribution of cognitive factors, such as expectancies, inthe maintenance of pain behaviors. As well, it suggests that fear and/or anxiety modi-fication techniques may be useful in the treatment of persistent pain.

Several other cognitively based models, more specific than that of Philips (1987),have also been proposed to account for persistent pain behavior. These include theFear Avoidance Model of Exaggerated Pain Perception (Lethem, Slade, Troup, & Bent-ley, 1983) and a recent cognitive model of fear of movement/(re)injury (Vlaeyen,Kole-Snijders, Boeren, & van Eek, 1995). The former, based on the general concept offear of pain, attempts to explain the process by which the emotional and sensory com-ponents of pain become desynchronous (i.e., why fear and avoidance remain while tis-sue damage remits) in some patients with chronic pain. The latter, based on the spe-cific fear that physical activity will cause reinjury, presents a possible pathway by which

FIGURE 1. A Model of Chronic Pain Avoidance Behavior. From “Avoidance Behaviour and Its Role in Sustaining Chronic Pain,” by H. Philips, 1987, Behaviour Research and Therapy, 25, p. 277. Copyright 1987 by Elsevier Science Ltd. Reprinted

with permission.


injured patients either become mired in a vicious fear cycle (characterized by cata-strophic thought, avoidance behaviors and physical disability) or successfully recover.It is apparent that the focus and specificity of each of these models differ; however,their basic premise is the same. Both models postulate two opposing responses to fearthat occur in the context of chronic pain—confrontation and avoidance. Confronta-tion is conceptualized as an adaptive response that is associated with behaviors thatpromote recovery and successful rehabilitation. Avoidance, on the other hand, isviewed as a maladaptive response, that leads to increased fear, limitations in activity,physical and psychological consequences that contribute to disability, and persistenceof pain in the absence of identifiable organic pathology. Below we focus on the empir-ical investigations that have addressed the postulates of these models.

Empirical Evaluation

In general, the findings of a number of empirical investigations support the notionsespoused by the aforementioned models. Some of the early works are discussed andreviewed elsewhere (Fordyce et al., 1982, Philips, 1987; Slade, Troup, Lethem, & Bent-ley, 1983). Below we focus on recent investigations that involve fear and avoidance inindividuals experiencing persistent pain associated with musculoskeletal injury. Al-though this is our focus here, it is, nevertheless, noteworthy that fear and avoidancehave been shown to be related to distress and disability in patients with chronic painof other origins (e.g., sickle cell disease, Gil, Abrams, Phillips, & Keefe, 1989; head-ache, Hursey & Jacks, 1992; Philips & Jahanshahi, 1985, 1986). In the following sec-tions we discuss empirical findings specifically related to (a) fear of pain, (b) fear ofphysical activity and work, and (c) nonpain fears.

Fear of pain.

Fear of pain (and of activities or events associated with pain) is a centralconstruct in the cognitive-behavioral models. Consequently, evaluating the role thatfear of pain plays in pain-related avoidance behavior and disability has been the focusof several recent investigations. To this end, McCracken and colleagues have pub-lished several studies that have advanced our understanding of the role that fear ofpain plays in pain persistence and disability associated with musculoskeletal pain.These studies stem directly from the development of the Pain Anxiety Symptoms Scale(PASS; McCracken, Zayfert, & Gross, 1992, 1993), a rationally derived four-factor scaledesigned to assess three dimensions of fear of pain (i.e., pain-specific fearful apprais-als, cognitive symptoms of anxiety, and physiological symptoms of anxiety) and pain-related escape and avoidance (e.g., analgesic medication use, activity restriction). Thepsychometric properties of the PASS appear favorable and studies conducted to datesuggest that its factor structure is reasonably stable. Confirmatory factor analysis (Os-man, Barrios, Osman, Schneekloth, & Troutman, 1994), conducted in a communitysample, has indicated support for the PASS as a four-factor model (Goodness of Fit

5

.963) and as a one-factor model (Goodness of Fit

5

.955). This suggests that both sub-scale and total scores may be useful in assessment. However, Larsen, Taylor, andAsmundson (1997) have indicated that a five-factor model may best describe the scaleand that some revisions are needed (e.g., division of the cognitive anxiety subscaleinto two components assessing cognitive interference and coping strategies). Forth-coming investigations should confirm which factor structure is most appropriate.

Based on the postulates of the avoidance models, McCracken and colleagues haveargued that cognitive, physiological, and behavioral responses to pain may, in some,


represent a phobic response that serves to maintain pain behavior. Consistent withthis hypothesis, they have found scores on the PASS to make significant and uniquecontributions to the prediction of both disability and interference with activities ofdaily living due to pain (McCracken et al., 1992). Specifically, the PASS was found tobe a better predictor of interference than was the sensory scale of the McGill PainQuestionnaire (MPQ; Melzack, 1975) (

sr

2PASS

5

.14;

sr

2MPQ

5

.0008), and the traitform of the State-Trait Anxiety Inventory (STAI; Spielberger, Gorsuch, & Luschene,1970;

sr

2PASS

5

.052;

sr

2STAI

5

.018). As well, the PASS was a better predictor of disabil-ity than was the sensory scale of the MPQ (

sr

2PASS

5

.17;

sr

2MPQ

5

.0015), the trait formof the STAI (

sr

2PASS

5

.094;

sr

2STAI

5

.008) and emotional distress as measured by theBeck Depression Inventory (BDI; Beck, Ward, Mendelson, Mock, & Erbaugh, 1961;

sr

2PASS

5

.068,

sr

2BDI

5

.035).McCracken, Gross, Sorg, and Edmands (1993) have found greater fear of pain to

correspond with greater anxiety (as measured on a numerical scale anchored as 0

5

no anxiety

to 100

worst anxiety imaginable

), and a greater restriction of range of motionin individuals with back pain who were asked to perform a passive straight leg raisetest. As well, fear of pain inversely corresponded to initial predictions of pain severity,although such predictions became more accurate on later trials. These findings sug-gest that fear of pain is associated with a tendency towards, at least initially, expecta-tion and overestimation of pain that, in turn, leads to restriction of movement duringtesting. In more general terms, these results support the hypothesis that fear of painleads to avoidance of pain-related experiences and contributes to disability.

The percentage of overestimates of pain, regardless of fear of pain, observed in theMcCracken, Gross, Sorg, and Edmands (1993) study were relatively low compared tothat of other studies. Specifically, the percentage of initial overestimates, underesti-mates, and accurate estimates that they reported were 19.5%, 38.4%, and 42.1%, re-spectively. By comparison, Rachman and Eyrl (1989) found the proportion of initialoverestimates, underestimates, and accurate estimates to be 43%, 24%, and 33%, re-spectively, in a sample of university students with recurrent headaches. Given the pos-tulated link between overestimation of pain (or fear of pain) and avoidance behavior(Rachman, 1994), the relative lack of overestimates in the chronic back pain patientsis interesting. This issue is further clouded by a recent study by Murphy, Lindsay, andde C Williams (1997), in which the majority of chronic low back pain patients under-predicted the pain on an initial physical task. As was found with patients in the Mc-Cracken, Gross, Sorg, and Edmands (1993) study, discrepancies between predictedpain and experienced pain were gradually corrected during subsequent physical tasks.A similar tendency towards initial underprediction of pain was found by Arntz and Pe-ters (1995), who noted, in an induced-pain experiment, that patients with chronicback pain tended to significantly underpredict degrees of pain, while healthy controlsubjects’ expectations of pain were reasonably accurate to the degree of pain they re-ported experiencing.

As suggested by McCracken, Gross, Sorg, and Edmands (1993), however, “persis-tent errors of prediction in either direction may relate to chronic pain” (p. 651).Moreover, the nature of the prediction may be mediated by fear of pain. That is, un-derpredictions may be associated with a low fear of pain and a failure to avoid whenavoidance behavior is warranted, whereas overprediction may be related to elevatedfear of pain and inappropriate avoidance. Consequently, assessing fear of pain mayprovide clinicians with the information they need to determine whether they shouldemphasize confrontation in their treatment protocol as, arguably, it may not be the


best strategy in all cases (i.e., confrontation, when not prudent, may lead to reinjuryand/or persistent pain).

Empirical evidence also suggests that the style of coping used by an individual todeal with pain can be an important determinant in their adjustment to pain. To illus-trate, coping strategies characterized by catastrophic cognitions and decreased feel-ings of personal control have been associated with greater dysphoria and decreasedfunctional capacity, whereas attention diversion has been associated with increasedpain intensity (Jensen, Turner, Romano, & Karoly, 1991). As well, beliefs that oneholds about pain and about their ability to engage in various pain coping strategiescan affect style of coping (Jensen, Turner, & Romano, 1991; Williams & Keefe, 1991).In the context of the current presentation, this leads to the question of whether fearof pain influences the way in which one copes with pain.

To date, McCracken and Gross (1993) have conducted the only study to address theaforementioned question. Using the PASS and the Coping Strategies Questionnaire(Rosenstiel & Keefe, 1983), they assessed 165 patients presenting primarily with com-plaints of chronic back pain. The Coping Strategies Questionnaire is a 65-item instru-ment that measures various methods of coping. Findings indicated that (a) cognitiveanxiety was related to deceased frequency of cognitive coping strategies and dimin-ished sense of control over pain, (b) physiological anxiety was associated with gener-ally enhanced coping, and (c) avoidance was related to increased use of pain behav-iors. Thus, the primary response modality through which fear of pain is expressed(i.e., cognitive, physiological, behavioral) appears to have implications for the strategywith which one attempts to cope with their pain. Notwithstanding, the nature of therelationship between coping strategies and fear of pain remains poorly understood.McCracken and Gross (1993) have argued that sequential placement of fear responsesto pain “antecedent to the coping responses makes intuitive sense because the formerare probably more immediate responses to pain, whereas coping may require addi-tional mediating responses” (p. 258). On the other hand, each may occur at a similartime during the sequence of events and may influence the other. Further empirical in-vestigation will clarify these issues.

Fear of physical activity and work.

Fear of pain has not been the only focus of investiga-tion. Indeed, specific situations and events directly associated with the pain experi-ence have also been studied. Waddell and colleagues (Waddell, Newton, Henderson,Sommerville, & Main, 1993) have recently studied the relationship between chronicback pain, disability, and pain-related fear and avoidance beliefs about physical andwork-related activities. To do so, they developed the Fear-Avoidance Beliefs Question-naire (FABQ), a 16-item measure that has acceptable validity. They revealed that pain-related fear-avoidance beliefs about work are the most specific and powerful factorsaccounting for disability and work loss associated with chronic low back pain. In fact,these beliefs were found to be stronger predictors of disability (adjusted

R

2

5

.46)than were biomedical measures of pain (e.g., anatomical pattern of pain, time patternof pain, severity of pain; adjusted

R

2

5

.14). These results confirm those reported byMcCracken et al. (1992) and provide further evidence of the importance of fear andavoidance in the persistence of pain behavior and related disability.

Likewise, recent investigations of kinesiophobia (i.e., fear of physical activity stem-ming from the belief that it will lead to pain, injury, or reinjury) are consistent withthe aforementioned results. Using a clustering procedure, Crombez and colleagues(Crombez, 1994; Crombez, Vervaet, Lysens, Baeyens, & Eelen, 1998) classified pa-


tients with low back pain as either Avoiders (

N

5

33) or Confronters (

N

5

16) andcompared their responses on self-report measures and a physical performance test.Confronters were characterized by a tendency to confront painful experiences. Onthe self-report measures, Avoiders reported greater fear of pain and greater fear of re-injury, even after controlling for group difference in pain frequency, intensity, andduration. As well, Avoiders indicated paying more attention to sensations in their backand reported more disability (both rated on 5-point scales anchored as 0

5

not at all

to5

5

very strongly

) and trouble with physical activity (as assessed by the short-version ofthe Sickness Impact Profile; Roland & Morris, 1983) than did Confronters; however,the groups did not differ in perceived level of control over pain. When exposed to aperformance test with the Cybex Knee-Extension-Flexion Unit, Avoiders demon-strated poorer performance, as measured by peak torque and the variability index(i.e., a measure used to denote interference due to pain or submaximal perfor-mance), than did the Endurers.

As an extension of the aforementioned study, Vlaeyen et al. (1995) conducted twostudies to assess the relationship of kinesiophobia with (a) biographical, pain-related,and distress-related variables and (b) behavioral performance. In the first study, 103patients with chronic low back pain completed a series of self-report questionnairesthat indicated, upon analysis, that kinesiophobia was related most strongly to cata-strophic cognitions and affective state. As well, both gender and compensation statuswere significant factors in the prediction of kinesiophobia, with males and those par-ticipants receiving disability compensation reporting greater kinesiophobia. In thesecond study, 33 patients with chronic low back pain were asked to stand, lift a 5.5-kgbag with their dominant arm, and hold it until pain or discomfort prevented continu-ation. Results indicated patients with high kinesiophobia were more trait anxious,held the bag for a shorter duration, and reported more state anxiety and fear (as mea-sured by a visual analog scale anchored

I am not afraid to reinjure myself

to

I have neverbeen so afraid to reinjure myself

) following termination than did those with low kinesio-phobia.

Nonpain fears.

Philips (1987) has suggested that when “assessing avoidance behaviorin chronic pain patients, it is important to consider more than the diminished levelsof activity and exercise” (p. 273). Similarly, in discussing cognitive and behavioralcomponents of avoidance, Lethem et al. (1983) have stated that each of these “typesof avoidance lead the individual to minimize or avoid physical and social activitiescompletely” (p. 404). These statements lead to the question of whether patients withpersistent pain are more likely to fear stimuli or experiences that are not directly re-lated to pain.

Empirical evidence, although preliminary, tends to affirm this question. For exam-ple, in their investigation of individuals with chronic headache pain, Philips and Ja-hanshahi (1986) found that the 6 factors of the 49-item Pain Behavior Checklist (PBC;Zarkowska, 1981; as cited in Philips & Jahanshahi, 1986) related to avoidance (ofhousework, daily mobility, activities, exercise, stimulation, and social situations) col-lectively accounted for 42.6% of the total scale variance. Notably, social avoidance wasthe most prominent behavior, accounting for 21.6% of the variance.

More recently, similar findings have been observed in some (Asmundson, Norton,& Jacobson, 1996; Vlaeyen et al., 1995), but not all (Dalton & Feuerstein, 1989), inves-tigations involving patients with chronic musculoskeletal pain. Vlaeyen (1991) has re-


ported elevated and clinically significant scores on the Social Phobia and Agorapho-bia subscales of the Fear Survey Schedule (FSS-III; Wolpe & Lange, 1964).Asmundson, Norton, and Jacobson (1996) have reported elevated levels of social andblood/injury, but not agoraphobic, fears, as measured by the Marks and Mathews(1979) Fear Questionnaire, in a sample of patients with chronic musculoskeletal pain.Chronic pain patients, compared to patient controls, were also found to be morelikely to report definite avoidance of particular social and blood/injury situations(Asmundson, Norton, & Jacobson, 1996). Dalton and Feuerstein (1989), on the otherhand, did not find any significant differences between their study groups (i.e., pa-tients with cancer pain, chronic noncancer pain, disability without pain, and healthycontrol subjects) on any FSS-III subscales except for Phobias. Patients with cancerpain and chronic noncancer pain scored higher on the Phobia subscale than did dis-abled patients without pain or healthy controls. Unfortunately, Dalton and Feuersteindid not specify the nature of the pain experienced by their noncancer pain group;thus, direct comparisons with the other studies are tentative at best.

Recent research in our laboratory has shown that a large percentage of people withchronic musculoskeletal pain, relative to the general population, meet

DSM-IV

(Amer-ican Psychiatric Association, 1994) criteria for social phobia (Asmundson, Jacobson,Allerdings, & Norton, 1996) and posttraumatic stress disorder (PTSD; Asmundson,Norton, Allerdings, Norton, & Larsen, 1998). Likewise, other investigators have re-ported a general increase in the prevalence of anxiety disorders in these individuals(see Asmundson, Jacobson, Allerdings, & Norton, 1996). One of the primary featuresof anxiety disorders is avoidance of cues associated with increased arousal and fear.For example, in the case of PTSD, this would include avoidance of internal and exter-nal cues related to the traumatic event. Although the general relationship betweenanxiety and chronic pain has been recognized for a number of years (Merskey &Boyd, 1978), the relationship between the conditions remains poorly understood. Al-though each may influence the other, our results suggest that fear and avoidance be-haviors in those with chronic musculoskeletal pain are exacerbated when the condi-tions occur comorbidly.

Collectively, these results suggest that patients with persistent musculoskeletal painfear a variety of situations that are not necessarily associated with pain. However, manyquestions remain with regard to the relationship of nonpain fears to persistent pain.Does fear generalize to situations closely associated to the experience of pain(Vlaeyen et al., 1995) such that nonpain fears arise as a consequence of musculoskele-tal injury? Do behaviors geared toward reduction of nonpain fears, for example,avoidance of social situations, serve to reinforce pain behaviors, including avoidance(Asmundson, Norton, & Jacobson, 1996)? Do nonpain fears exist premorbidly and re-flect a generalized tendency to respond with fear to a variety of aversive stimuli? An-swers to these questions may enhance our understanding of pain persistence and ourability to provide effective intervention.

General Summary

The avoidance models suggest that avoidance and fear play a primary role in themaintenance of pain and related behaviors. To differing degrees the models discusscognitive, social, and personal factors that contribute to fear and avoidance and,hence, to the maintenance of pain and disability. The empirical evidence indicates


that fear of pain and fear of pain-related experiences and activities, combined withavoidance behavior, may be more disabling than pain itself. As well, it seems that pa-tients with persistent pain have a tendency to fear a variety of situations and stimulithat are not necessarily related to pain, but which may play a significant role in the de-velopment and/or maintenance of persistent pain behavior. In the following sectionswe explore two factors that may, to some degree, mediate or contribute to pain-re-lated fear and associated avoidance behaviors—attentional processes and anxiety sen-sitivity.

ATTENTIONAL PROCESSES AND CHRONIC MUSCULOSKELETAL PAIN

Pain, from a biological perspective, is critical in promoting survival and, thus, our atten-tion may be primed to process painful stimuli at the expense of other attentional de-mands (Crombez, 1997). Regarding diversion of attention, Crombez (1997) states, “Ifpain functions to afford behavioral repair through escape, this requires automatic pre-paratory action sequences which can not easily be inhibited” (manuscript p. 11). Todate, there have been relatively few studies that address the issues of selective attentionand distraction in patients with chronic pain. Nonetheless, available data suggest that at-tentional processes may be influenced by variables such as pain intensity and fear of pain.

Selective Attention

Pearce and Morley (1989), utilizing a modified Stroop paradigm, examined the im-pact of pain on attention in a study investigating the validity of the MPQ (Melzack,1975). In essence, the modified Stroop paradigm involves the presentation of words,varying in emotional valence, to which subjects are asked to name the color that theword is presented while ignoring its meaning. Delays in color naming, or Stroop inter-ference, occur when the meaning of the word attracts the subject’s attention despitetheir efforts to attend solely to the color of the word. These delays have been inter-preted as being indicative of selective attentional processing. Sixteen subjects whowere experiencing chronic pain (location not specified) were tested. Stimulus wordswere generated from both the Sensory and Affective scales of the MPQ, and negativeemotional words were generated to control for the potential effect of emotional dis-turbance. In general, the results of the study indicated that pain patients, relative tocontrol subjects, had increased Stoop interference for pain-related but not negativeemotion words. This pattern of results seems to indicate that chronic pain patientshave “a more salient cognitive representation of both sensory and affective compo-nents of pain” (Pearce & Morley, 1989, p. 120) and, moreover, suggests that they maybe selectively attending to such cues.

Asmundson, Kuperos, and Norton (1997) attempted to replicate the findings ofPearce and Morley (1989) using a dot-probe paradigm. The dot-probe was selected inresponse to MacLeod’s (1991) suggestion that the Stroop may not be a pure measureof attentional bias. Nineteen chronic musculoskeletal pain patients and 22 controlsubjects completed the dot-probe task as well as the BDI and Anxiety Sensitivity Index(ASI; Peterson & Reiss, 1992). The latter measure has been shown to be related to fearof pain (Asmundson & Norton, 1995; Asmundson & Taylor, 1996). Sixteen pain-re-lated words (e.g., stabbing, sharp) selected from the MPQ-Short Form (Melzack,1987) and 16 injury-related words (e.g., accident, strain) provided by clinicians with


extensive experience treating chronic pain were paired with neutral control words.An extra 140 pair of neutral control words were compiled from previous dot-probestudies. Testing involved presentation of word pairs on a computer monitor, some ofwhich were followed by a dot-probe presented with equal probability in the spatial lo-cation of either word in each pairing. Subjects were instructed to read the top word ofeach word pairing aloud, and to respond with a key press as quickly as possible uponseeing the dot-probe. Attentional biases are inferred when detection latencies to dot-probes that follow in the same spatial location as target cues are speeded relative tothose presented in the spatial location of neutral cues.

In contradiction to the findings of Pearce and Morley (1989), the results of theAsmundson et al. (1997) study revealed no significant differences between groups intheir responses to dot-probes that followed either the pain-related words or the injury-related words. Inclusion of BDI scores as a covariate did not alter these results; how-ever, when chronic pain patients were divided into high ASI and low ASI groups, anal-ysis revealed that low ASI (and, by inference, low fear of pain) patients shifted atten-tion away from the words related to pain. No such effect was found with subjects in thehigh ASI group. The authors posit that these individuals may not fully attend to pain-related characteristics of environmental stimuli or activities and, as such, may fail toavoid them. As mentioned earlier, failure to avoid when prudent to do so (e.g., in theearly stages of physical trauma) may lead to persistent pain through overexertion, re-peated reinjury, and inappropriate healing of damaged tissue (McCracken, Gross,Sorg, & Edmands, 1993).

Distraction

In a related line of investigation, Eccleston (1995) has conducted a two-part experi-ment to explore the ability of chronic pain patients to shift attention away from painduring attentionally demanding tasks. The first part of the study involved 22 chronicpain patients and 11 nonpain control subjects, performing numerical interferencetasks. The chronic pain patients were divided into high (

n

5

11) and low pain (

n

5

11) groups based on a median split of pain scores obtained from a visual analoguescale of pain intensity. Two cards containing several numbers each were presented tothe participants and they were asked to either report the largest single value on eithercard (simple task) or report the total number of digits on the card with the largernumber of digits (complex task). The latency to report the correct response from thetime the cards were presented was the dependent measure. Although there were nodifferences in reaction time between the groups on the simple task, the high paingroup took significantly longer on the complex task than did either the low pain orcontrol group (who did not differ significantly from each other).

In the second part of the study, Eccleston (1995) further explored the low paingroup to determine if their performance was the result of either psychoanalgesia dur-ing the attentionally demanding task or “fast-switching” of attention between the painstimuli and the numerical interference task. Both the psychoanalgesia theory and thefast-switching theory are discussed at length by Eccleston (1995). The subjects were re-cruited to perform a numerical interference task again and, in this case, were re-quired to report the largest value on the first pair of cards presented (simple task inpart one of the study), report the total number of digits on the card with the largernumber of digits (complex task in part one of the study), and continue to alternatebetween the simple and complex tasks on subsequent presentations. The author hy-


pothesized that this uncued switching “is much more demanding of attentional re-sources than performing the tasks alone” (Eccleston, 1995, p. 398). Neumann Keulspost hoc test of the results for part two of the study revealed that the high pain groupperformed the task significantly slower than did either the low pain or control group(who, again, did not differ from each other). Eccleston (1995) interprets these resultsas supporting the psychoanalgesia explanation of performance for the low pain groupin that “enough of the available resources were allocated to the processing of the de-manding interference task to disallow the entry of the pain stimuli into consciousness”(p. 400). The performance of the high pain group, however, may have been ham-pered by their inability to ignore the pain stimuli.

The impact of acute pain on attention was studied by Crombez, Eccleston, Baeyens,and Eelen (1996). Using reaction time to an auditory stimulus as the dependent mea-sure, they assessed the attentional interference of pain from electrical stimulationcompared to interference from the presentation of a neutral control image (i.e., im-age of a human face). Results from initial trials (i.e., tone presented 100 ms after stim-ulus onset) indicated reaction time was significantly slower during the pain conditionin comparison to the control condition. Later trials (i.e., tone presented 1,500 ms af-ter stimulus onset), however, showed a decreased reaction time during the pain con-dition to the extent that it no longer differed significantly from reaction times duringthe control condition. These results demonstrate that experimentally induced painhas a disruptive effect upon attentional processing and that disruption is most markedimmediately after pain onset.

In a similar study, Crombez, Eccleston, Baeyens, and Eelen (1997) examined thepossibility that the distractive nature of pain decreases with repeated exposure. Sub-jects were required to perform an auditory discrimination task while being subjectedto a neutral distracter or a painful electrical stimulus. This process was repeated a sec-ond time to explore changes in pain-related interference following repeated expo-sures to pain. During the first set of trials, significant decreases in reaction time werenoted when either the painful distracter and the neutral distracter were presented;however, the second set of trails with the same subjects indicated that only the neutraldistracter failed to continue to interfere with attention. Thus, despite repeated pre-sentation, the painful distracter continued to impair the participants’ ability to per-form well on the attentionally demanding task.

Summary

Is the information processing system of the chronic musculoskeletal pain patientprimed to selectively process pain-related stimuli? Although the results of Pearce andMorley’s (1989) modified-Stroop investigation suggest that this may be the case, thefindings of Asmundson et al. (1997) caution that the allocation of attentional pro-cesses may be mediated, in part, by one’s dispositional tendency to fear pain. This lat-ter finding is in line with reports in the literature indicating that people with anxietydisorders selectively attend to stimuli that are specifically related to their fear (for re-view, see Logan & Goetsch, 1993). It was also noted that chronic pain patients withlow levels of pain are able to shift attention away from pain stimuli (Eccleston, 1995)and that specific parameters of the acute pain experience (e.g., temporal relationshipto other relevant stimuli) may diminish its attention-grabbing quality. Together, thesefindings raise question as to whether attentional processes are consistent across all pa-tients who experience chronic pain or whether there are subgroups of patients for


whom these processes differ as a function of some factor for which we currently havelimited understanding, such as fear of pain. Additional research is needed to clarifythis issue.

ANXIETY SENSITIVITY AND PAIN

Despite the apparent link between pain, fear, and avoidance behavior, few investiga-tions have directly examined factors that impact on the propensity of individuals withchronic pain to respond with fear and avoid experiences and activities associated withpain. That is, there has been little investigation of variables that influence fear andavoidance in individuals with persistent pain. This, however, may be an area of investi-gation that holds important implications with respect to (a) our understanding of theprocesses that maintain pain behaviors over time, (b) strategies for treatment and,perhaps, (c) preventing persistence of pain and pain behaviors following injury. We(Asmundson & Norton, 1995; Asmundson & Taylor, 1996) have speculated that theanxiety sensitivity construct (Reiss, 1991; Reiss & McNally, 1985) may prove useful inthis regard. Below we will review the construct and emerging evidence that supportsthis hypothesis.

Anxiety Sensitivity

Anxiety sensitivity is typically defined as the fear of anxiety symptoms (e.g., palpita-tions, dizziness, gastrointestinal upset) arising from the belief that they will haveharmful social, somatic, and/or psychological consequences (Reiss, 1991; Reiss & Mc-Nally, 1985). To illustrate, palpitations will be feared if one believes that they will leadto cardiac arrest; dizziness will be feared if one believes that it is associated with cardio-vascular accident; and gastrointestinal upset will be feared if an individual believesthat it will lead to social humiliation.

The expectancy model of fear (Reiss, 1987, 1991; Reiss & McNally, 1985) posits thatanxiety sensitivity is one of three fundamental trait sensitivities (the others being sen-sitivities to illness/injury and to negative evaluation) that amplify an array of fear reac-tions and phobias. Accordingly, if one has a dispositional tendency to fear symptomsof anxiety, then there is an increased probability that the individual will fear and/oravoid a multitude of other stimuli (e.g., animals, hospitals, blood) and/or situations(e.g., social-evaluative situations, agoraphobic situations) (also see McNally & Lorenz,1987; Reiss, Peterson, Gursky, & McNally, 1986). Several empirical investigations haveprovided support to this proposition (Taylor, 1993; Taylor & Rachman, 1992; also seeReiss, 1991), indicating that individuals with high anxiety sensitivity, compared to thosewith lower levels, do have a greater tendency to fear numerous stimuli and/or situations.

To date, the majority of investigations incorporating anxiety sensitivity and the ASI(Peterson & Reiss, 1992), a widely used measure of the anxiety sensitivity construct,have focused on the role that this dispositional trait plays in panic attacks, panic disor-der and, to a lesser extent, the other anxiety disorders. Furthermore, there has been anumber of investigations as of late exploring the relationships between anxiety sensi-tivity and other conditions such as asthma (Carr, Lehrer, Rausch, & Hochron, 1994)and alcohol abuse (Stewart, Peterson, & Pihl, 1995). The reader is referred to recentarticles by McNally (1996), Taylor (1995, 1996), and Lilienfeld (1996) for a review ofcurrent findings and controversial issues in this area of investigation.


Anxiety Sensitivity and Chronic Musculoskeletal Pain

Emerging evidence suggests that anxiety sensitivity plays a role in the fear and avoid-ance responses of patients with persistent pain. In a preliminary investigation of thisissue, we (Asmundson & Norton, 1995) assessed 70 patients with chronic back pain us-ing a comprehensive self-report battery, including the ASI and the PASS. Patientswere classified as having high (

n

5

14), medium (

n

5

44), or low (

n

5

12) levels ofanxiety sensitivity based on the sample mean and standard deviation. Comparisons be-tween groups indicated that patients with high anxiety sensitivity had higher levels ofpain-related cognitive anxiety, pain-related fear, and general negativity of affect eventhough the groups did not differ in pain severity. As well, 71% of patients with highanxiety sensitivity, compared to 34% and 25% of patients with medium and low anxi-ety sensitivity, reported current use of analgesic medication to relieve pain symptoms.High anxiety sensitivity has been associated with the use of substances that reducearousal (McNally, 1996); thus, it may be the case that the higher rate of analgesic con-sumption on part of the patients with high anxiety sensitivity represents an attempt toalleviate and/or avoid aversive aspects of the pain experience.

Further, we observed that the ASI and the subscales of the PASS were moderatelycorrelated (see Table 1). Correlations with cognitive anxiety were strongest (

r

5 .62),followed by fear of pain (r 5 .48), physiological anxiety (r 5 .38) and escape/avoid-ance (r 5 .32). Scores on the ASI also correlated significantly with feelings of self-con-trol (r 5 2.29) and negative affect (r 5 .41), but not with perceptions of social sup-port or pain-related interference with activities of daily living. Partial correlations,controlling for pain severity, did not differ significantly from the aforementioned sim-ple correlations.

On the basis of these initial results, we concluded that pain-related fear and avoid-ance, as well as other aspects of distress associated with chronic pain, might be signifi-

TABLE 1. Comparison of Simple and Partial Correlations (Controlling for Pain Severity) Between Anxiety Sensitivity and Pain-Related Cognitive/Affective Variables

Anxiety Sensitivity

Simple r Partial r

Cognitive anxietya 0.62*** 0.61***Physiologic anxietya 0.38*** 0.36**Escape/avoidancea 0.32* 0.30*Fear of paina 0.48*** 0.46***Social supportb 0.04 0.02Self-controlb 20.29* 20.29*Pain interferenceb 0.18 0.12Negative moodb 0.41*** 0.39***

aMeasures from the Pain Anxiety Symptom Scale.bMeasures from the Multidimensional Pain Inventory.From “Anxiety Sensitivity in Patients With Physically Unexplained Chronic Back Pain: A Prelim-inary Report,” by G. J. G. Asmundson and G. R. Norton, 1995, Behaviour Research and Therapy, 33,p. 775. Copyright 1995 by Elsevier Science Ltd. Reprinted with permission.*p , 0.02 (two-tailed).**p , 0.005 (two-tailed).***p , 0.001 (two-tailed).


cantly influenced by the dispositional tendency to respond fearfully to anxiety-relatedbodily sensations. In other words, we felt that anxiety sensitivity may play a significantrole in the cognitive and behavioral presentations of individuals with chronic pain. Ina subsequent study, we (Norton, Hutton, Asmundson, & Cruickshank, 1995) foundfurther evidence to support this notion. Anxiety sensitivity was identified as a strongpredictor of pain-related distress, as measured with the 32-item Coping With Health,Injuries and Problems Scale (CHIPS; Endler, Parker, & Summerfeldt, 1993). Morespecifically, Norton et al. (1995) administered the ASI, CHIPS, and a number of otherquestionnaires to a sample of 87 consecutive patients presenting to a pain clinic with avariety of pain complaints. Regression analysis revealed that scores on the ASI and theNeuroticism scale of the NEO-Five Factor Inventory (Costa & McCrae, 1989) were thebest predictors of pain-related distress, accounting for 21.2% and 22.1% of the vari-ance, respectively. Pain severity ratings and specific nature of pain complaint, on theother hand, did not add significantly to the prediction of pain-related distress.

Recently we (Asmundson & Taylor, 1996) have used structural equation modelingto test the predictions that (a) anxiety sensitivity directly exacerbates fear of pain andthat (b) anxiety sensitivity indirectly exacerbates pain-related avoidance via its effectson fear of pain (see Figure 2). Participants in this study were 259 patients with com-plaints of chronic pain related to musculoskeletal injury, primarily involving the back.The results supported both predictions, even after controlling for the direct influenceof pain severity on avoidance behavior. In short, the findings support the hypothesisthat high anxiety sensitivity exacerbates fear of pain and thereby promotes avoidancebehavior.

Further evidence for the influence of anxiety sensitivity on patients with chronicpain is provided by Asmundson et al. (1997). As reported earlier, a dot-probe para-digm was employed to assess whether chronic pain patients selectively attend to pain-and injury-related information. No attentional bias differences were found betweenthe chronic pain patients and a sample of pain free controls. However, when the

FIGURE 2. Path Diagram for Model of Anxiety Sensitivity, Fear of Pain, and Pain-Related Escape/Avoidance Behavior. From “Role of Anxiety Sensitivity in Pain-

Related Fear and Avoidance,” by G. J. G. Asmundson and S. Taylor, 1996, Journal of Behavioral Medicine, 19, p. 582. Copyright 1996 by Plenum Publishing Corporation.

Adapted with permission.


chronic pain patients were divided into high and low ASI groups, it was found thatthose patients with low ASI scores shifted attention away from pain-related wordswhereas those with high anxiety sensitivity responded similarly regardless of the wordtype or position. This finding is somewhat paradoxical in that the direction of the ef-fects is opposite to that expected on the basis of the anxiety disorders literature (i.e.,that patients with high anxiety sensitivity will shift attention toward salient threat ma-terial); nonetheless, the results do suggest that attentional processes in patients withchronic pain may be mediated by anxiety sensitivity.

Summary

Collectively, these results provide compelling evidence to suggest that anxiety sensitiv-ity affects the way one responds, both cognitively and behaviorally, to pain-related situ-ations and events. The results of our initial investigations are intriguing, but, ofcourse, there is considerably more investigation required in this area. Notwithstand-ing, the results are consistent with current positions (Reiss, 1991; Taylor, 1995) thatmany fears can be reduced to more basic fears. In particular, one may become fright-ened of pain-related experiences and situations, and engage in avoidance behavior,partly because they are frightened of the aversive anxiety-related (and often, somatic)sensations that accompany those situations.

CLINICAL IMPLICATIONS

The avoidance models discussed in preceding sections have been proposed in an at-tempt to better understand the process through which pain and pain behaviors be-come persistent. Although each model has unique components, the general patterninvolves a number of pathways initiated by musculoskeletal injury and nocioception,mediated by individual difference variables, with progression to maladaptive avoid-ance behavior and disability. As noted, these models hold many similarities to thoseproposed to explain avoidance behavior seen in other phobic states (Marks, 1969)and anxiety disorders (Barlow, 1988). The results of our investigations may add an im-portant dimension to the current models—that anxiety sensitivity is an important andclinically relevant factor that influences pain and related disability through its influ-ence on fear of pain and avoidance behavior. Based on this, we can speculate that in-terventions effective in reducing anxiety sensitivity and panic (e.g., Craske & Barlow,1989) may also reduce pain-related fear and avoidance behaviors and, ultimately, in-crease the efficacy of rehabilitation efforts. Below we briefly outline assessment andtreatment implications that stem from the above review.

Assessment

The consistent indication that fear is associated with the suffering and disability thatoften accompany chronic musculoskeletal pain suggests that clinicians working withthese individuals should conduct a careful assessment of fear and avoidance, bothpain-related and otherwise. Although a discussion of comprehensive assessment of thechronic pain patient is beyond the scope of this article, its should be noted that a mul-timodal assessment designed to encompass physical, social, behavioral, cognitive and


affective components should be conducted whenever possible (e.g., Turk & Rudy,1987). For gaining information specific to pain-related fear and avoidance there are anumber of self-report questionnaires, discussed below, that may be useful.

Zarkowska (1981; as cited in Philips & Jahanshahi, 1986) developed the PBC, a 49dichotomous (yes/no) item checklist, to assess pain-related behaviors along three ra-tionally derived dimensions (a) avoidance (e.g., “avoid lifting objects”), (b) complaint(e.g., “sigh, moan, cry out”), and (c) help-seeking (e.g., “have back massaged”). Phil-ips and Jahanshahi (1986) conducted a comprehensive examination of the PBC with asample of patients suffering from chronic headache, to assess its reliability and valid-ity. Test-retest analysis noted significant reliability for all three dimensions. The test-retest reliability coefficient for the help-seeking dimension (r 5 .53, p 5 .004), al-though statistically significant, was considerably lower than that of the avoidance di-mension (r 5 .77, p 5 .001) and the complaint dimension (r 5 .70, p 5 .001). Basedon these results, Philips and Jahanshahi (1986) suggest caution when interpretingscores along the help-seeking dimension. Factor analysis of the PBC data failed to sup-port the PBC as a three-factor model. Rather, a 13-factor structure, accounting for60.5% of the variance, was indicated when the data was subjected to exploratory factoranalysis. Interestingly, six of the 13 dimensions categorized avoidance of various be-havior categories (social, housework, daily mobility, activities, daily exercise, and stim-ulation), further demonstrating the significance of avoidance in pain behavior.

Recently, McCracken, Gross, Aikens, and Carnrike (1996) compared several of themeasures mentioned in the above review and assessed their ability to predict differentdimensions of pain and pain behaviors. Results of correlational analyses indicatedthat each subscale of the PASS and the FABQ were significantly related to pain disabil-ity as measured with the Pain Disability Index (PDI; Pollard, 1984) and avoidance asmeasured with the PBC (Philips & Jahanshahi, 1986). As well, the PASS was signifi-cantly related to pain intensity as measured by the MPQ. Stepwise regression analysisindicated that the physiological subscale of the PASS was the only measure studiedwhich made a significant independent contribution (R2 5 .39) to the prediction ofpain severity. Pain-related disability was strongly predicted (R2 5 .54) by the combina-tion of MPQ pain severity, PASS escape and avoidance responses, and FABQ avoid-ance of work activities. The PASS escape and avoidance subscale (R2 5 .29) was theonly unique significant predictor of Avoidance (PBC), PASS fear (R2 5 .16) was thesole significant contributor to the prediction of Complaints (PBC), and FABQ workand PASS escape and avoidance together predicted 26% of the variability in PBCHelp-seeking. Consequently, these measures, combined, appear to provide a reason-ably comprehensive assessment of the multiple response modalities of pain-relatedfear (also see Asmundson, Hale, & Hadjistavropoulos, 1996).

Given the apparent relationship between selective attention and fear of pain, itseems reasonable that an assessment of attention toward pain may prove useful. ThePain Vigilance and Awareness Questionnaire (PVAQ; McCracken, 1997) is a new 16-item questionnaire purporting to assess the degree to which individuals attend topain. Items are scored on a 0 (never) to 5 (always) scale, and are summed to obtain asingle measure of attention to pain. McCracken (1997) reports that the PVAQ pos-sesses acceptable internal consistency and demonstrates validity in relation to otherquestionnaire-based measures of attention and body awareness. Furthermore, step-wise multiple regression results indicate that the PVAQ contributes significantly to theprediction of fear of pain, depression, psychosocial disability, and physician visits dueto pain, beyond that already accounted for by pain severity. The PVAQ, however, has


not yet been validated using cognitive paradigms that measure selective attention,such as the modified Stroop or the dot-probe tasks.

Finally, although not designed specifically for use in patients with chronic pain, the16-item ASI (Peterson & Reiss, 1992) is a measure that may be very useful in assessingfear and avoidance in these patients. As discussed above, levels of anxiety sensitivityare positively associated with, and predictive of, both fear of pain and pain-relatedavoidance behavior (including the likelihood of analgesic use). Moreover, given itsdispositional nature (McNally, 1994), anxiety sensitivity may represent a vulnerabilityfactor that mediates one’s tendency to become fearful, avoidant, and disabled follow-ing musculoskeletal injury. Consequently, anxiety sensitivity may serve as a factor use-ful in early identification of those at increased risk for becoming disabled by pain andpain behaviors that persist beyond the time expected for healing of organic pathol-ogy. Further investigation, incorporating prospective and longitudinal evaluations,will be necessary to evaluate this hypothesis.

Assessing pain-related fear and avoidance behaviors may afford the clinician withvaluable information with which to tailor treatments. For example, a thorough assess-ment of fear of pain may provide clinicians with the information necessary in deter-mining whether confrontation of pain and pain-related stimuli or events should beemphasized in treatment—the clinician may wish to engage the patient in confronta-tion exercises in the case of high scores on the PASS or the ASI, whereas encouraginginitial avoidance may be most prudent for those with low scores on these measures. Al-though these specific recommendations have not yet been empirically evaluated, rec-ognition of the heterogeneous nature of chronic pain has led to efforts geared towardtailoring treatments to meet the needs of specific categories of patients. We briefly dis-cuss treatment issues, particularly as they relate to fear and avoidance, in the followingsection.

Treatment

It is beyond the scope of this article to comprehensively discuss treatment issues asthey pertain to chronic pain. Nor can we provide complete coverage of treatments de-signed with the intent of reducing specific fears and associated avoidance behaviors.However, given the central roles that fear and avoidance play in the lives of many pa-tients with chronic pain, we will briefly outline some treatment options that may serveto reduce related suffering and functional disability.

As discussed above, there is a strong association between anxiety sensitivity, fear ofpain, and pain-related avoidance behaviors. On this basis, it is reasonable to speculatethat chronic pain patients with high levels of anxiety sensitivity (and fear of pain) willgain considerable benefit from treatments designed to reduce anxiety sensitivity.These treatments comprise a number of specific techniques developed for treatingpanic disorder (e.g., Craske & Barlow, 1989) and may, for example, include (a)breathing retraining, (b) relaxation training, (c) cognitive restructuring, (d) expo-sure to somatic stimuli, and (e) exposure to external stimuli. Similar techniques arecurrently used in the treatment of patients with chronic pain (e.g., see Keefe, Crisson,Urban, & Williams, 1990; Turk, Meichenbaum, & Genest, 1983; Turk & Melzack,1992; Turk & Rudy, 1988); consequently, their application to treating anxiety sensitiv-ity would not require major changes to the general treatment approach but, rather,minor adjustments to treatment focus. We expect that the reduction of anxiety sensi-tivity will be associated with a reduced tendency to catastrophically misinterpret sensa-


tions of arousal that are associated with pain and that this should, in turn, be reflectedin a reduction of fear of pain and associated avoidance behaviors. To date, however,there have been no systematic evaluations of the efficacy of treating anxiety sensitivityin patients with chronic pain.

An important and relatively new method of treating individuals with high anxietysensitivity is to intentionally provoke symptoms of anxiety and to see that they are con-trollable and/or that they do not produce catastrophic outcomes (Barlow & Cerny,1988). A similar approach might be effective for patients with chronic musculoskeletalpain. For example, they might be encouraged to bend, lift or engage in other behav-iors that provoke mild sensations of pain and then to either engage in relaxation exer-cises to reduce pain or to see that feared consequences do not automatically follow.This approach may also allow the individual an opportunity to correct their tendencytoward inaccurate estimates of pain severity. An important aspect of this approachwhen applied to the chronic pain patient, and one that cannot be overemphasized, isthat proper care is taken to ensure that the task used to induce the pain sensationdoes not lead to reinjury. Although we are aware of no controlled trials in this area, itis possible that pain sensation stimulated peripheral to the original site of injury maybe as equally effective for the exposure exercise as those stimulated in the area of ini-tial injury. This issue awaits empirical evaluation.

Finally, people with specific phobias often avoid stimuli or situations that are associ-ated with their specific fear (American Psychiatric Association, 1994). To reduce theirfear they are encouraged to systematically spend more time with the feared stimuli orin the feared situations. This is often done, at least initially, in the presence of thetherapist. People with chronic pain who avoid activities or situations because of fear ofinjuring or embarrassing themselves might benefit from a similar type of gradual ex-posure to feared situations. Likewise, in the case of significant social fears, the applica-tion of treatment strategies designed for patients with social phobia (e.g., Heimberg,Juster, Hope, & Mattia, 1995) may a prudent initial step. Again, future investigationsare needed to systematically evaluate the efficacy of such an approach across the vari-ous categories of fear evidenced in patients with chronic musculoskeletal pain.

It is important to emphasize that gaps exist in our current knowledge pertaining tothe treatment of pain-related fear and avoidance. Although the aforementioned treat-ment suggestions may prove useful in the alleviation of some of the suffering and func-tional disability experienced by fearful chronic pain patients, particularly when combinedwith other appropriate modalities of treatment (e.g., physical therapy, occupationaltherapy, exercise), continuing research is needed in this area.

Future Directions

As noted above, there are several practical issues related to the treatment of pain-related fear and avoidance that require further investigation. There are, in addition,other more basic issues that have yet to be resolved. For example, the evidence forpain-related attentional biases in patients with chronic pain is mixed. Future investiga-tions in this area are needed to clarify the extent to which selective attention (a) is me-diated or influenced by fear of pain, (b) is related to clinical severity, and (c) general-izes across various conditions involving chronic pain. This latter issue is also importantwith regard to the relationship between anxiety sensitivity and fear of pain, as currentinvestigations have focused primarily on patients with chronic musculoskeletal pain.Moreover, because the exploration of anxiety sensitivity in patients with chronic pain


is in its infancy, there are many other issues that warrant empirical attention. Some ofthe more salient issues include (a) determining whether the anxiety sensitivity modelor an alternate explanation, such as general negativity of affect, provides the most ac-curate account of the factors that influence fear of pain and avoidance in individualswith persistent pain, (b) adding behavioral testing to protocols designed to assess theimpact of anxiety sensitivity on avoidance and disability, and (c) identifying which ofanxiety sensitivity and fear of pain is the more basic fear.

CONCLUSIONS

To understand the way in which a person responds to persistent pain we must looknot only at the physical parameters, but beyond to consider factors such as cognitions,coping strategies, life events, and personality. This article has focused on reviewingthe theoretical and empirical literature regarding fear of pain and avoidance behav-iors in patients with chronic musculoskeletal pain. Models of pain-related fear andavoidance have many parallels to those regarding other phobic states and anxiety dis-orders. Like fear, chronic pain is potentially disabling. The literature suggests thatfear (of pain, of movement/(re)injury, and of situations or stimuli not directly relatedto pain) plays a significant role in pain-related avoidance and, in many cases, disabil-ity. It is important to realize, however, that there is considerable variability in fear re-sponses to pain. Through awareness of this variability, and its consequences, we canbetter understand why some people respond poorly to medical approaches to reduc-ing their musculoskeletal pain. Moreover, by way of proper assessment and identifica-tion of fear in people who experience persistent pain, we can move towards effectivetreatment through inclusion of protocols geared toward the diminution of phobic be-havior.

Acknowledgment—Preparation of this article was supported, in part, by a grant to thefirst author from the Health Services Utilization and Research Commission. The au-thors thank Drs. Steve Taylor, Geert Crombez, and Thomas Hadjistavropoulos and twoanonymous reviewers for their insightful comments on an early draft of this article.

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