The results suggest that none of these constructs is primarily associated with pain perception, calling for research examining the interrelationships between fear of pain, pain-related anxiety, and anxiety sensitivity. The constructs are believed to be factorially and theoretically distinct [4], [5] and [9], which is supported by the small to moderate correlations between these variables presented in the current data; however, more research is needed to determine if these represent independent or overlapping constructs in the context of pain perception. Perhaps a higher-order factor, such as fear of physical discomfort or negative attitudes toward pain, explains why these 3 variables are associated with hyperalgesia. Nevertheless, results from the regression analyses suggest that these constructs are not redundant. Indeed, anxiety sensitivity predicted unique variance in increased heat and cold pain tolerance in women and heat pain in men (ie, hypoalgesia), a relationship that was not present with fear of pain and pain-related anxiety. This novel finding contradicts previous reports that anxiety sensitivity is associated with decreased pain tolerance [39]. Methodological differences, such as the method of pain induction (ie, digitally controlled thermode vs cold pressor) or the variables controlled for may have allowed the identification of this unexpected finding, which leaves room for interpretation. One possibility is that anxiety sensitivity facilitates a form of stress-induced analgesia, a pain suppression response occurring when facing anxiety-provoking stimuli [2]; however, why this would be unique to anxiety sensitivity is unknown. Alternatively, this finding could represent a statistical artifact; but, given the effect was identified in both sexes and in different pain trials and modalities, this seems relatively unlikely. More research is needed to explore this phenomenon.