Sex differences in the long-term stability of forehead cold pressor pain

The purpose of this study was to examine sex differences in the stability of experimental pain responding across time. Stability was assessed by using 2 forehead cold pressor applications separated by 9 months. Twenty-eight men and 20 women completed both Session 1 and Session 2. Repeated measures analysis of variance showed a main effect for Session on maximum pain level. Women reported significantly more pain at Session 2, whereas men showed no difference between sessions. There were no differences on pain report between men and women at Session 1. A significant Session by Sex interaction was associated with perceived chronic stress and trait anxiety levels. At Session 2 but not Session 1, women endorsed a significantly greater expectation than men to experience unpleasant aftereffects from the cold pressor task. Additional analysis showed that chronic stress and trait anxiety were significantly associated with sex-specific pain responding. We propose that the influence of a prior painful incident on an identical repeated painful experience differs between men and women. We speculate that this influence is related to sex differences in psychological mechanisms used to interpret painful stimuli within the context of remembered experiences. To our knowledge, this is the first report of sex differences in the long-term stability of an experimental laboratory pain stimulus, controlling for follicular phase of the female menstrual cycle. Perspective: This study examines sex differences in the stability of experimental pain responding across a 9-month period We speculate that psychological mechanisms influence one's interpretation of a prior painful incident and that this interpretation facilitates increased pain reporting in response to an identical repeated exposure, as was observed for women. (C) 2004 by the American Pain Society