JohanW.S.Vlaeyen.PhD

In the late 20th century, several pain researchers studying the clinical differences between acute and chronic back pain, observed that pain of recent onset was associated with a pattern of physiological responses seen in anxiety attacks. In contrast, chronic pain would be more characterized by a habituation of autonomic responses and by a pattern of vegetative signs seen in depressive disorders. It has only been recently that fear responses were studied in chronic back pain as well. One of the striking findings was that the specific fear of pain, or fear of injury, appeared to be more disabling than the pain itself (Crombez et al., 1999). The early notion that the lowered ability to accomplish tasks of daily living in chronic pain patients is merely the consequence of pain severity had to be reconsidered. Indeed, a steadily increasing number of studies are showing that pain-related fear is indeed one of the most potent predictors of observable physical performance and self-reported disability levels in sub-acute and chronic pain (Asmundson et al.. 1999 : Vlaeyen and Linton. 2000).

Based on earlier work on fear and avoidance processes in chronic pain (Lethem et al.. 1983 : Philips. 19S7). Vlaeyen et al. (1995) presented a cognitively oriented model of pain-related fear which is presented in figure 1. This model serves as a heuristic aid and ties several findings in the more recent literature together concerning the role of fear-avoidance in the development of musculoskeletal pain problems. It postulates two opposing behavioral responses : confrontation and avoidance, and presents possible pathways by which injured patients get caught in a downward spiral of increasing avoidance, disability and pain. The model predicts that there are several ways by which pain-related fear can lead to disability : (1) Negative appraisals about pain and its consequences, such as catastrophic thinking, is considered a potential precursor of pain-related fear (McCracken and Gross. 1993). (2) Pain-related fear will be associated with increased psychophysiological reactivity, when the individual is confronted with situations that are appraised as "dangerous", and which may make physical activity more painful (Vlaeyen et al., 1999). (3) Just like other forms of fear and anxiety, pain-related fear interferes with cognitive functioning. Fearful patients will attend more to possible signals of threat (hypervigilance) and will be less able to shift attention away from pain-related information. This will be at the expense of other tasks including actively coping with problems of daily life (Peters et al., 2000). (4) Fear is characterized by escape and avoidance behaviors, of which the immediate consequences are that daily activities (expected to produce pain) are not accomplished anymore. Avoidance of daily activities results in functional disability (Asmundson et al.. 1997). (5) Because avoidance behaviors occur in anticipation of pain rather than as a response to pain. these behaviors may persist because there are fewer opportunities to correct the (wrongful) expectancies and beliefs about pain as a signal of threat of physical integrity. Fearful beliefs may thus become dissociated from actual pain experiences. (6) Longstanding avoidance and physical inactivity has a detrimental impact on the musculoskeletal and cardiovascular systems, leading to the so-called "disuse syndrome' (Bortz. 1984). both in terms of deconditioning (Wagenmakers et al.. 1988) as in guarded movements (Watson et al.. 1997). In addition, avoidance also means the withdrawal from essential reinforcers leading to mood disturbances such as irritability, frustration and depression. Both depression and disuse are known to be associated with decreased pain tolerance level (Romano & Turner 1985 . McQuade et al 1988). and hence they might promote the painful experience.

References
1) Asmundson GJ, Norton GR. Allerdings MD. Fear and avoidance in dysfunctional chronic back pain patients. Pain 1997 : 69(31 : 231-6.
2) Asmundson GJ. Norton PJ, Norton GR. Beyond pain : the role of fear and avoidance in chronicity. Clin Psychol Rev 1999 : 19( 11 : 97-1 19.
3) Bortz W.M., The disuse syndrome. West. J. Vied.. 141 (1984) 691-694.
4) Crombez. G, Vlaeyen JW. Hours PH. l.ysens R. Pain-related tear is more disabling than pain itself : evidence on the role of pain-related tear in chronic back pain disability. Pain 1999 : 80( 1-21 : 329-39.
5) Lethem J. Skide PD, Troup JD, Bentley G. Outline of a fear-avoidance model of exaggerated pain perception : I. 1983 : 21(4) : 401-408.
6) McQuade. K.J.. Turner, J.A. and Buchner. D.M.. physical fitness and chronic low back pain. Clin. Orthop. Rel. Res.. 233 11988) 198-204.
7) Peters ML. Vlaeyen JWS. van Drunen C. (2000) Hypervigilance for innocuous somaiosensory stimuli in fibromyalgia patients. Application of a body scanning reaction time paradigm. Pain (in press).
8) Philips HC. Avoidance behaviour and its role in sustaining chronic pain. Behav Res Ther 19S7 : 25(4) : 273-9.
9) Romano. J.M. and Turner. J.A.. Chronic pain and depression, Docs the evidence support a relationship Psychol. Bull.. 97 11985) 31 1-318.
10) Vlaeyen JW. Seelen HA. Peters M, de Jong P. Aretz E. Beisiegel F., et al. Fear of movement/I re (injury and muscular reactivity in chronic low back pain patients : an experimental investigation [In Process Citation]. Pain 1999 . 82(3) : 297-304.
11 Vlaeyen JW. Kole-Snijders AM. Boeren RG. van Eek H. Fear of movemeniyireiinjury in chronic lev. back pain and its relation to behavioral performance. Pain 1995 : 62(3) : 363-72.
12) Vlaeyen JW. Pinion SJ. Fear-avoidance and its consequences in chronic musculoskeleial pain : a siale ol'ihe art. Pain 2000 : 85(3) : 317-332.
13) Wagenmakers. A.J.M., Coakley, J.H. and Edwards. R.H.T. The metabolic consequences of reduced habitual activities in patients with muscle pain and disease. Ergonomics. 31 (1988) 1519-1527.
14) Watson. P.. Booker, CK. Main, C.J. and Chen. A.C.N. Surface electromyography in the identification of chronic low back pain patients :
the development of the flexion relaxation ratio. Clinical Biomechanics. 12 (1997) 165-171.

Figure 1. A cognitive-behavioural model of pain-related fear (based on Vlaeyen et al., 1995). If pain, possibly caused by an injury, is interpreted as threatening (pain catastrophizing), pain-related fear evolves. This leads to muscular reactivity, hypervigilance, and avoidance behaviors. Longterm avoidance may subsequently increase levels of disability, disuse and depression. The latter will maintain the pain experiences thereby fueling the vicious circle of increasing fear and avoidance. In non-catastrophizing patients, no pain-related fear and rapid confrontation with daily activities is likely to occur, leading to fast recovery.

Pain in Europe III. EFIC 2000, Nice, France, September 26-29, 2000. Abstracts book, p. 54 - 55.