Other: Psychological factors that predict pain sensitivity

Abstract

To date, few studies using laboratory pain-induction techniques have examined whether psychological characteristics influence pain threshold or tolerance. Although several studies have focused on introversion and extraversion, the results of these studies have been variable and the clinical significance of these variables can be questioned. The ego strength (Es Scale) and lassitude-malaise (Hy3) are two subscales of the Minnesota Multiphasic Personality Inventory that have been found to predict the response of pain patients to rehabilitation programs. Numerous validity studies have demonstrated that high scorers on the Es Scale tend to be resourceful, responsible and do not report major emotional difficulties, whereas high scorers on the Hy3 scale often report feeling discontent and vague somatic complaints. The success of these two groups in rehabilitation could be caused by differences in pain sensitivity. The objective of this study was to determine whether psychological factors such as ego strength predict baseline pain sensitivity. Sixty-six undergraduates participated in a within-subjects design in which they underwent two different laboratory pain-induction procedures: a radiant heat technique for pain threshold and a cold-pressor task for pain tolerance. Pain intensity was assessed with the visual analogue scale after each pain task. There were no gender or age differences on the Es or Hy3 scale. These data are based only on a subset of the data obtained to date. A significant relationship was observed between ego strength and pain sensitivity following the cold-pressor procedure (r = -.377, p < .036), but not following the radiant heat procedure. No significant associations were observed between Hy3 and pain sensitivity. The Es and Hy3 scales were inversely related (r =-.504, p < .004), as expected. These results suggest that ego strength may influence one's ability to tolerate aversive stimulation, even in non-clinical situations. Further, these findings underscore the importance of assessing this variable in clinical settings.