Impact of written emotional disclosure of trauma on laboratory induced pain
This study was undertaken to determine whether written emotional disclosure of trauma impacted capsaicin induced pain immediately after writing and at a one-month follow-up, and the extent to which a lifetime history of trauma alters pain under neutral conditions. Three experiments were conducted to answer these questions. In Experiment 1 participants were randomly assigned to write about either a neutral or a trauma topic, and they concurrently completed the capsaicin test. In Experiment 2, the capsaicin test was administered to trauma history and no trauma history participants and pain ratings and secondary hyperalgesia were recorded under neutral conditions. In Experiment 3, participants wrote for three days and completed the radiant heat test before writing on day 1 and after writing on day 3. They also completed the capsaicin test on either day 4 or at a one-month follow-up (day 30). Taken together, these studies had several important results. First, radiant heat withdrawal latencies, ratings of pain intensity and unpleasantness, and area of secondary hyperalgesia were all significantly increased when participants had a history of traumatic experiences. This is evidence that trauma history is sufficient to alter pain regulatory mechanisms, and this may be attributable to the chronic negative affective state induced by trauma history and sensitization of shared circuits involved in both pain and emotion. Furthermore, our findings suggest that written emotional disclosure may lead to long-term changes in pain modulatory pathways that regulate central sensitization, without altering systems that regulate spontaneous pain.