(447) Does trauma exposure affect temporal summation of pain and the nociceptive flexion reflex?

Trauma exposure and posttraumatic stress disorder (PTSD) are related to enhanced pain in response to suprathreshold stimuli and are often associated with the development of chronic pain. However, the mechanisms underlying the relationships between trauma exposure and pain have not been thoroughly explored. One potential mechanism is central sensitization (hyperexcitability of spinal neurons to pain signals). Temporal summation of pain is a laboratory paradigm believed to assess central sensitization. The present study assessed temporal summation of the nociceptive flexion reflex (TS-NFR a physiological marker of spinal nociception) and temporal summation of pain (TS-Pain) in response to repeated, painful, electrical stimulations over the ankle in 184 healthy men and women. Prior to testing, the Life Events Checklist (LEC-5) was administered to assess the number of traumatic events that happened to them, and this was used to form 3 levels of exposure (ie, low [0-1], medium [2-3], high [≥4]). Linear mixed model ANOVAs found that all groups demonstrated significant TS-NFR and TS-Pain; however, the degree of summation was greatest in the high exposure group (p<.05). TS-NFR and TS-Pain were similar in the other groups (ps>.05). These findings suggest that greater trauma exposure is associated with greater amplification of pain and spinal nociception. Future research should examine potential psychosocial (eg, PTSD symptoms, catastrophizing, emotion regulation) or biological (eg, allostatic load) factors that mediate the relationship between trauma exposure and enhanced TS-NFR and TS-Pain. Further study is necessary to determine whether these markers of central sensitization might contribute to the development of PTSD and/or chronic pain syndromes in those who are exposed to multiple traumatic events.