Cognitive biases in chronic pain

Empirical studies of information processing biases in chronic pain have explored selective attention, interpretation of meaning and memory/recall. It has been argued that information-processing biases could maintain or exacerbate pain in different ways: Attentional biases may increase monitoring of physical sensations, hypervigilance, and therefore pain behaviours; interpretation bias may increase interpretation of sensations as painful; recall bias may increase distress and may impact on self-image, which can reduce healthy behaviour and increase actual damage (Pincus 1998; Waddell 1996). Biased information processing has been viewed as a risk factor for the development of chronic disability and has been shown to predict higher health care costs (Pincus and Morley 2002; Pincus and Newman 2001).

Attention bias

Attention is probably the most extensively investigated cognitive process in relation to pain. Most studies on the detection of attention biases towards pain stimuli have relied on experimental paradigms such as the emotional Stroop task and the visual dot-probe task. Although some studies found support for attention biases in pain patients using these paradigms, these results seemed to be difficult to replicate in other studies and seemed to depend on the specific task and the exact type of stimulus material that were used to assess the bias such as sensory pain words, affective pain words or pictoral stimuli (Asmundson et al. 1997, 2005; Asmundson and Hadjivropoulos 2007; Roelofs et al. 2002, 2005). However, the most recent studies found attentional biases towards sensory-related but not affective words using large sample sizes (Dehghani et al. 2003; Sharpe et al. 2009). In healthy people with elevated levels of pain-related anxiety, results on the occurrence of attention bias towards pain-related stimuli showed more consistency (Asmundson et al. 1997, 2005; Keogh and Cochrane 2002; Keogh et al. 2001a, 2001b), although failures in replicating these findings have been reported as well (e.g. Roelofs et al. 2003a, 2003b). The observation of more consistent findings in healthy people and inconsistent findings in pain patients might suggest that the paradigms tested were not sufficiently difficult for chronic pain patients who might have learned to allocate their attentional resources in the continuous presence of actual pain (Pincus and Morley 2001). In a similar view, Asmundson et al. (2005) proposed that the use of sensory and affective pain words as threatening stimuli might fail in assessing attention biases in patients because these stimuli are not threatening enough for pain patients, in contrast to healthy persons who are not suffering from persistent pain. In conclusion, emotional Stroop and dot- probe paradigms might suffer from low ecological validity due to the use of verbal and pictorial stimulus material. Several studies in which an ecologically more appropriate paradigm has been used (i.e. the primary task paradigm), have demonstrated the attention demanding properties of pain, and the interruptive effect that pain can have on the allocation of attention to other tasks (e.g. Crombez et al. 1998a, 1998b; Eccleston and Crombez 1999; Peters et al. 2002). In the primary task paradigm, the effect of the administration of electrical pain stimuli on the performance of a simple cognitive task (e.g. distinguishing high and low pitch tones) is examined. The resulting interruptive effect of pain on attention has proven to be amplified by the intensity, novelty, unpredictability, and threat value of the pain stimulus (Eccleston and Crombez 1999), and atten- tional interference has been found to be pronounced in persons high in pain catastrophizing and fear of pain (Carleton et al. 2005; Crombez et al. 1998a, 1998b). Other studies have demonstrated that attention shifts to pain and pain-related cues and, once detected, pain is difficult to disengage from (e.g. Koster et al. 2006; Van Damme et al. 2004a). Based on this line of research, it can be concluded that there is initial evidence that pain demands attention, both in pain patients, but also in healthy individuals with high levels of specific pain-related fears, which has led to the development of a neurocognitive model of attention to pain, including behavioural and neuroimaging evidence (reviewed in Legrain et al. 2009; Van Damme et al. 2010).

In sum, it can be concluded that there is accumulating evidence for a sensory-related atten- tional bias in chronic pain (Boissevan 1994; Crombez et al. 2000; Pearce and Morley 1989; Snider et al. 2000; Sharpe et al. 2009), and specifically there is some evidence to suggest that anxiety in the presence of pain may be associated with interference (Asmundson et al. 1997; Boissevan 1994; Pincus et al. 1998; Snider et al. 2000).

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