Pain and masochistic behaviour: The role of descending modulation.

Background: The mechanisms of pain perception in individuals with masochistic behaviour (MB) remain poorly documented. We hypothesized that MB is associated with context-specific changes in descending pain modulation.

Methods: We compared the effects of four standardized sets of images with positive (erotic), negative (mutilations), masochistic or neutral emotional valences on the RIII nociceptive reflex evoked by electrical stimulation of the sural nerve and recorded on the ipsilateral biceps femoris in 15 controls and 15 men routinely engaging in MB. We systematically assessed the RIII reflex threshold and recruitment curves (up to the tolerance threshold), thermal (heat and cold) pain thresholds measured on the upper and lower limbs and responses to the pain sensitivity questionnaire, to compare basal pain perception between our two groups of participants. We also assessed anxiety, depression, empathy, alexithymia, high sensation seeking and catastrophizing, to investigate their potential influence on the emotional modulation of pain.

Results: Thermal pain thresholds, RIII reflex recruitment curves, and responses to the psychological and pain sensitivity questionnaires were similar in the two groups. Neutral, positive and negative images modulated the RIII reflex similarly in the two groups. By contrast, masochistic images induced a significant (p < 0.01) decrease in RIII reflex responses in subjects with MB, whereas it tended to increase these responses in control subjects.

Conclusions: Our data suggest that psychological profile, basal pain sensitivity and the emotional modulation of pain are normal in individuals with MB but that these subjects selectively engage descending pain inhibition in the masochistic context.

Significance: Decrease pain perception related to masochistic behaviours is associated with specific activation of descending pain inhibition.