Original Reports Dysfunctional Pain Modulation in Torture Survivors: The Mediating Effect of PTSD Ruth Defrin,* Yael Lahav, y,z and Zahava Solomon y *Department of Physical Therapy, Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel-Aviv University, Tel-Aviv, Israel. y Bob Shapell School of Social work, Tel-Aviv University, Tel-Aviv, Israel. z Department of Psychology, University of Southern Denmark, Odense, Denmark. Abstract: Trauma survivors, and particularly torture survivors, suffer from high rates of chronic pain and posttraumatic stress disorder (PTSD) for years afterward, along with alterations in the function of the pain system. On the basis of longitudinal data on PTSD symptomatology, we tested whether exposure to torture, PTSD or PTSD trajectories accounted for chronic pain and altered pain percep- tion. Participants were 59 torture survivors and 44 age-matched healthy control subjects. Chronic pain was characterized. Pain threshold, pain tolerance, conditioned pain modulation (CPM), and tem- poral summation of pain were measured. Three PTSD trajectories were identified among torture sur- vivors; chronic, delayed, and resilient. Lack of CPM and more intense chronic pain was found among the chronic and delayed groups compared with the resilient and healthy control groups. Temporal summation of pain was strongest among the chronic group. PTSD trajectories mediated the relation- ship between torture and CPM. It appears that the duration and severity of posttraumatic distress, rather than the exposure to trauma, are crucial factors that mediate the association between trauma and chronic pain. Because PTSD and its resultant distress are measurable, their evaluation seems particularly important in the management of pain among trauma survivors. The results may be gener- alized to other instances in which chronic pain persists after traumatic events. Perspective: This article presents the mediation effect of PTSD trajectory on pain modulation among trauma survivors suggesting that it is the duration and severity of PTSD/distress, rather than the exposure to trauma per se, that influence the perception and modulation of pain. ª 2016 by the American Pain Society Key words: Posttraumatic stress disorder trajectories, chronic pain, pain modulation, trauma, torture. S urvivors of traumatic events are known to suffer from the coexistence of chronic pain and posttrau- matic stress disorder (PTSD), the mechanism of which is still not clear (for review see Asmundson and Katz, 6 and Moeller-Bertram et al 37 ). War captivity, which usually entails deliberate human cruelty through the infliction of physical and psychological torture, is one of the most severe traumatic experiences. Physical torture in captivity may include severe beating, burning, penetrating injuries, suspension, and electric shocks directed toward vulnerable body parts. Psychological torture may include isolation, humiliation, and mock ex- ecutions. Torture survivors are thus at an increased risk for physical and mental distress and dysfunction. 21 Although the immediate suffering in captivity is evident, the long-term effect of torture on the body in general, and on the pain system in particular, has received limited scientific attention. High rates of chronic pain among torture survivors, ranging from 60% to 94%, have been reported. 3,9,43,71,74,75 Clinical and psychophysical testing on the feet of torture survivors who underwent foot beating (falanga) revealed thermal and tactile hypo- or hyperesthesia and mechanical allodynia. 52-54,71 Psychophysical testing in intact body regions of torture survivors revealed abilities poorer than control subjects to modulate pain manifested in abolished conditioned pain modulation Received January 24, 2016; Revised May 22, July 18, and September 9, 2016; Accepted September 14, 2016. The study was supported by a grant from the Israeli Science Foundation. The authors have no conflicts of interest to declare. Address reprint requests to Prof Ruth Defrin, PhD, Department of Physical Therapy, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv 69978 Israel. E-mail: rutidef@post.tau.ac.il 1526-5900/$36.00 ª 2016 by the American Pain Society http://dx.doi.org/10.1016/j.jpain.2016.09.005 1 The Journal of Pain, Vol 18, No 1 (January), 2017: pp 1-10 Available online at www.jpain.org and www.sciencedirect.com