اضطراب درد در بیماران مبتلا به درد مزمن: هراس خاص یا جلوه ای از حساسیت اضطرابی؟

Rather than viewing anxiety among chronic pain patients as simply a component of negative affectivity, investigators have developed a model of “pain anxiety” in which patients develop fear and avoidance of activity linked to pain. We examined whether pain anxiety can be conceptualized as a specific phobia, or whether evidence supported the notion that pain anxiety is better understood as a manifestation of anxiety sensitivity in the context of chronic pain. Chronic musculoskeletal pain patients (N=70) underwent cold pressor and mental arithmetic tasks while cardiovascular, self-report, and behavior indexes were recorded. They completed measures of pain anxiety, anxiety sensitivity, fear of negative evaluation, depression and trait anxiety. Correlation analyses showed pain anxiety was related to pain-relevant responses during cold pressor, but it was also related to evaluation-relevant responses during cold pressor, and to pain- and evaluation-relevant responses (including subtraction accuracy) during mental arithmetic. Regression analyses showed that almost all effects of pain anxiety on task responses were accounted for by anxiety sensitivity. Fear of negative evaluation, in contrast, correlated only with evaluation-relevant responses, and mostly during mental arithmetic. These effects remained significant when depression, trait anxiety, or anxiety sensitivity were statistically controlled. Pain anxiety may be an expression of anxiety sensitivity rather than a circumscribed phobia; a distinction that could profitably guide treatment strategies.

Theory and research indicate that anxiety is an important emotional concomitant of chronic pain. Not only are measures of trait anxiety at least moderately correlated with such indexes of adjustment as pain severity and perceived disability (e.g., McCracken, Gross, Aikens, & Carnrike, 1996), but chronic pain patients appear to suffer disproportionately from anxiety disorders (Asmundson, Jacobson, Allerdings, & Norton, 1996; Asmundson, Norton, Allerdings, Norton, & Larsen, 1998). A straightforward conceptualization of these empirical findings is that anxiety is a component of the pronounced negative affectivity experienced by patients afflicted with chronic pain. That is, anxiety may be viewed as just one symptom of a general malaise also composed of depression and suppressed anger. Another view of how anxiety and chronic pain are linked borrows from Mowrer’s two-factor model of fear conditioning (1947), and conceptualizes chronic pain syndromes as products of fear and avoidance (Lethem, Slade, Troup, & Bentley, 1983; Philips, 1987). According to the two-factor model, fear is originally learned through classical conditioning, and the fear behavior is then maintained by avoiding the cues that have become associated with fear and anxiety. Fears are difficult to extinguish because individuals learn to avoid fear- or anxiety-provoking situations. Applied to chronic pain, the two-factor theory would suggest that individuals first experience fear or anxiety during activity that has become painful due to injury or other pathology, become anxious when faced with the prospect of such painful activity, and then avoid the activities associated with the possibility of experiencing pain or reinjury. Although adaptive in the short run as it promotes healing of damaged tissue, “avoidance behavior” may come to be maintained and generalized less as an attempt to escape noxious sensory stimuli, but more as an effort to reduce anxious arousal in anticipation of pain. Seen perhaps by the individual as a way to control and reduce pain, avoidance instead may lead to overprediction of pain severity (Rachman, 1994), and to reduced opportunities to have experiences that “disconfirm” the implicit belief that pain should be feared (Philips, 1987). Far from viewing anxiety among pain patients as merely one element of an elevated but diffuse negative affectivity, anxiety becomes the engine of a phenomenon akin to a specific phobia variously labeled pain anxiety (McCracken, Zayfert & Gross, 1992), fear-avoidance (Waddell, Newton, Henderson, Somerville, & Main, 1993), or kinesiophobia (Kori, Miller, & Todd, 1990). Support has accumulated for the view that pain anxiety and avoidance is a kind of specific phobia. One overarching concern in this research has been to demonstrate that pain anxiety is a construct distinct from negative affect and trait anxiety. If this is indeed the case, then scales designed to tap pain anxiety (e.g., the Pain Anxiety Symptoms Scale; PASS; McCracken et al., 1992) should account for variance in chronic pain adjustment criteria beyond that accounted for by measures of negative affect and trait anxiety. Several studies have shown that pain anxiety scales predict significant increments in variance in various measures of disability when indexes of negative affect and even pain severity are controlled (e.g., McCracken et al., 1992; Crombez, Vlaeyen, Heuts & Lysens, 1999; Strahl, Kleinkecht, & Dinnel, 2000). Thus, what is accounted for in patient reports of disability by pain anxiety in particular may not be entirely reducible to, or explainable by negative affect or trait anxiety in general. A second concern has been whether pain anxiety is associated with actual behaviors that signal avoidance. A few studies have defined avoidance behaviors in terms of performances on physical capacity evaluations typically administered by physical and/or occupational therapists (Burns, Mullen, Higdon, Wei, & Lansky, 2000; McCracken, Gross, Sorg, & Edmands, 1993a; Vlaeyen, Kole-Snijders, Boeren, & van Eek, 1995). The activities performed during such evaluations produce fatigue and pain in many patients with chronic musculoskeletal pain, but patients afflicted with pain anxiety were expected to experience substantial anxiety and thus limit their exertions. Consistent with theory, results of these studies revealed that pain anxiety was correlated negatively with amount of weight carried and held, and range of motion. Moreover, for Burns et al. (2000), the deleterious effect of pain anxiety on weight carrying remained significant even when depression, trait anxiety and pain severity were statistically controlled. Investigators argue that, taken together, findings indicate not only that anxiety specific to pain exists independently from trait anxiety, but that it accounts for the kinds of behaviors expected from an individual who fears pain: namely, avoidance of activity. A third conceptualization of anxiety in chronic pain views it as a manifestation of an underlying predisposition to fear symptoms of anxiety (for review, see Asmundson, Norton, & Norton, 1999). Reiss and colleagues (Reiss & McNally, 1985; Reiss, Peterson, Gursky & McNally, 1986) proposed that the fear of fear is a disposition toward the development and maintenance of anxiety disorders. According to their expectancy model (Reiss, 1991), fear of fear is composed of anxiety expectancy and anxiety sensitivity. The former refers to the arousal of anxiety when an individual is presented with a stimulus perceived as causing possible physical harm. The latter refers to beliefs assigned to the personal experience of anxiety as a cause of illness, further anxiety or embarrassment. The expectation of, and sensitivity to anxiety symptoms together may drive avoidance behavior observed in individuals suffering from anxiety disorders (e.g., panic disorder). Individuals with anxiety sensitivity attribute catastrophic meaning to symptoms of anxiety, and so may come to fear and avoid a variety of stimuli or situations which evoke, or are associated with the physical sensations of anxiety. According to Asmundson and colleagues (e.g., Asmundson & Norton, 1995; Asmundson & Taylor, 1996; Asmundson et al., 1999), anxiety sensitivity may drive the avoidance and functional disability of chronic pain patients due to fear of physically unexplained pain. A chronic pain patient with anxiety sensitivity may happen to fear pain and avoid activity because the perception of alarm or arousal experienced when pain occurs is not dissimilar to anxious arousal. In this view, pain is feared because it is associated with what is truly feared: sensations of anxiety. Again, far from viewing anxiety in chronic pain as a mere facet of ubiquitous misery, in Asmundson’s extension of Reiss’ model, it becomes an expression of a more fundamental sensitivity to anxiety symptoms. Pain anxiety, then, is seen as a kind of fear manifested in the presence of a persistently painful condition, but which is rooted in an individual’s predilection to fear anxiety symptoms, irrespective of the source. To date, only a few studies have addressed this notion, but the evidence supports it. If anxiety sensitivity inclines an individual with persistent pain to develop pain anxiety, then measures of these constructs should be at least moderately correlated, and some indication should emerge that any effects of pain anxiety on disability or avoidance are at least partly attributed to anxiety sensitivity. Asmundson and Norton (1995), and Asmundson and Taylor (1996) found the Anxiety Sensitivity Index (ASI; Reiss et al., 1986) and the fear of pain subscale of the PASS to correlate r=0.48 and r=0.55, respectively, whereas Zvolensky, Goodie, McNeil, Sperry, and Sorrell (2001) reported the ASI and PASS total scale to correlate r=0.72. Also, Asmundson and Taylor (1996) found support for a path model in which anxiety sensitivity operates indirectly on avoidance via a direct effect on fear of pain. Results of this path model, albeit preliminary and correlational, suggest that anxiety sensitivity may exacerbate pain anxiety, which in turn leads to greater avoidance. Many studies of pain anxiety have used a research strategy that involved partitioning overlapping variance among self-report questionnaires. Although evidence suggests that measures of pain anxiety uniquely account for fear and avoidance responses to chronic pain, reliance on self-report measures, taken at cross-section, may have inflated effects between variables due to shared method variance. Other studies focused on measures of behavior recorded by observers, and upheld conclusions that pain anxiety predicts fearful responses to pain-inducing stimuli. These latter studies, however, employed only pain-inducing stimuli. Recall that Asmundson’s view of pain anxiety proposes that it is rooted in anxiety sensitivity. Thus, patients with high pain anxiety may exhibit fearful responses not only to pain-induction, but to a range of potentially anxiety-provoking stimuli as a function of a predisposition to fear anxiety symptoms. To determine whether pain anxiety is best conceived of as a specific phobia, or as an expression of anxiety sensitivity in the context of chronic and often inexplicable pain, fearful responses to situations other than painful ones need to be observed. If pain anxiety is best conceptualized as a kind of specific phobia, in which anxiety has become fixed to pain inasmuch as the latter originally signaled reinjury, then individuals high on such fear should be vulnerable to painful stimuli in particular. Thus, individuals with high pain anxiety should evince pronounced responses denoting fearfulness to pain-induction procedures, whereas their responses to other potentially anxiety-provoking situations should be less conspicuous. If, instead, pain anxiety is best conceived of as the expression of anxiety sensitivity in the context of chronic pain, then individuals with high pain anxiety should be vulnerable to a multiplicity of situations in which symptoms reminiscent of anxiety are experienced. That is, because fearful responses during pain would be driven by an underlying fear of anxiety symptoms, individuals with high pain anxiety should respond fearfully to pain induction, as well as to other kinds of potentially anxiety-provoking situations. In the present study, we evaluated the specific phobia versus anxiety sensitivity hypotheses by using a trait x situation approach. A sample of chronic pain patients underwent a cold pressor, which was intended to elicit pain anxiety, and they performed a mental arithmetic task, which was intended to elicit social evaluative anxiety. If pain anxiety is akin to a specific phobia, then PASS scores should significantly predict cardiovascular, self-report and behavior responses signifying fear of pain in particular, and only during the cold pressor. Moreover, these effects should remain significant even with measures of negative affect, trait anxiety, or ASI scores statistically controlled. Alternatively, if pain anxiety is simply a manifestation of anxiety sensitivity, then PASS scores should significantly predict cardiovascular, self-report and behavior responses connoting general fearfulness during both cold pressor and mental arithmetic. Moreover, these effects should be held largely in common with ASI scores. In addition, we included a trait measure of social evaluative concerns (Fear of Negative Evaluation scale; FNE; Watson & Friend, 1969) to provide a potential validation check of our trait×situation manipulations. We were concerned that even if PASS scores significantly predicted fearful responses to both tasks, we could not rule out that a circumscribed pain anxiety had indeed been aroused by a laboratory situation in which all participants knew via informed consent that pain would be induced at some point. However, if FNE scores then significantly predicted responses denoting social anxiety only during mental arithmetic, such findings would lend credibility to our claims to have evoked specific fears during the specific tasks.