Sex differences in responsiveness to painful and non-painful stimuli are dependent upon the stimulation method

Sex differences in thermo- and electrocutaneous responsiveness to painful and non-painful stimuli were investigated in 20 women and 20 men. Heat pain, warmth, and cold thresholds were assessed on the hand and foot with a Peltier thermode system. In addition, subjects used magnitude estimation to judge the sensation intensity evoked by temperatures ranging from 38°C to 48°C applied to the forearm. To measure detection, pain, and tolerance thresholds of electrocutaneous sensitivity, electrical pulses were administered to the hand. Magnitude estimates of sensation intensity were assessed for stimuli ranging from 0.5 mA to 4.0 mA. There were no sex differences in heat pain, warmth and cold thresholds. There were significant sex differences in electrical detection, pain and tolerance thresholds, with lower thresholds in women. Correspondingly, magnitude estimates were similar in women and men when using thermal stimuli while women judged stimuli from 2.5 mA on as more intense than men when using electrical stimuli. Despite these discrepancies, the measures for pain responsiveness from the two stimulation methods correlated significantly. In contrast, no significant correlations between the methods were found when considering the responsiveness to non-painful stimuli. The findings help to clarify controversies in the pain literature about sex differences. Results affirming and denying such differences could be obtained within a single sample, with stimulation method as the critical variable.