Examining emotional modulation of pain and spinal nociception in Native Americans: a preliminary investigation.

Pain problems are more prevalent in Native Americans than in any other group in the U.S., and this might result from group differences in pain modulation. This study was designed to examine emotional modulation of pain and spinal nociception in healthy, pain-free Native Americans (n = 21) relative to non-Hispanic Whites (n = 20). To assess emotional modulation of pain and the nociceptive flexion reflex (NFR, a physiological measure of spinal nociception), participants underwent a well-validated emotional picture-viewing paradigm during which suprathreshold pain stimuli were delivered to the ankle. Compared to Whites, Native Americans reported less pleasure to erotic pictures and failed to show corrugator reactivity to mutilation pictures. Unlike Whites, Native Americans only evidenced pain inhibition in response to erotica, but no pain facilitation (disinhibition) to mutilation pictures. Emotional modulation of NFR was similar in both groups. These preliminary findings suggest that Native Americans failed to disinhibit pain, perhaps due to over-activation of pain inhibitory mechanisms. Chronic over-activation of this system could ultimately exhaust it, thus putting Native Americans at future risk for chronic pain.