UBC Theses and Dissertations
Pain perception in chronic pain patients : a signal detection analysis Mahon, Mary L.
The purpose of this investigation was to examine the supposition that chronic pain patients (CPPs) have altered pain perception. Two models were examined that led to opposing predictions as to how CPPs would respond to painful stimuli (i.e., the hypervigilance and adaptation-level models). Both predictions have been supported by past research but because of methodological variation and the type of pain disorder studied, it has remained unclear under what circumstances the predictions of these two models may be met. The responses of pain patients to painful stimuli have been found to vary for patients-with different clinical presentations (i.e. those with and without medically incongruent signs and symptoms). Therefore, the present investigation sought to compare the responses to radiant heat stimuli of sixty CPPs (thirty with and thirty without a medically incongruent pain presentation) to thirty age and sex matched normal control subjects (i.e., pain-tree individuals). Signal detection theory methodology was used in order to separately evaluate sensory sensitivity and the response bias to report sensations as painful. In addition, cognitive and affective factors were assessed in order to identity potential psychological correlates of altered pain perception. The results of this study indicated that the presence of a medically incongruent pain presentation distinguished patients on their subjective report of disability and to a lesser extent cognitive appraisal and affective distress regarding their pain condition. They did not differ in their responses to painful stimuli. In a post hoc analysis where CPPs were classified into 'organic' and 'functional’ diagnostic groups, significant differences in pain threshold and the response bias to report pain were found. Patients classified as 'organic' had significantly higher pain thresholds compared to normal control subjects and patients classified as 'functional'. Differences in pain threshold were primarily represented by the response' bias to report sensations as painful rather than sensory sensitivity to the stimuli. The 'functional' group had a slightly lower pain threshold than the normal control group but this difference was not significant. The results are discussed in light of the two models of pain perception. The two methods used to classify pain patients are discussed according to their orthogonal characteristics on sensory, cognitive, and affective components.
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