• Henrik B Vaegter, Tonny E Andersen, Mathea Harvold, Per G Andersen, and Thomas Graven-Nielsen.
• Pain Research Group, Pain Center South, Odense University Hospital.
• Clin J Pain. 2018 Apr 1; 34 (4): 313-321.

ObjectivesPosttraumatic stress disorder (PTSD) is prevalent in chronic pain, and associated with increased pain, hyperalgesia, and psychological distress. This study aimed to investigate antinociceptive and pronociceptive pain mechanisms, pain intensity, and psychological distress (depression, anxiety, pain catastrophizing, and fear of movement) in patients with accident-related chronic spinal pain with (N=44) and without (N=64) comorbid PTSD characteristics.Materials And MethodsCuff algometry was performed on lower legs to assess pressure pain threshold (cPPT), tolerance (cPTT), temporal summation of pain (increase in pain scores to 10 repeated stimulations), and conditioning pain modulation (increase in cPPT during cuff pain conditioning on the contralateral leg). Warmth detection threshold and heat pain threshold at the hand were also assessed. Clinical pain intensity (numerical rating scale), psychological distress, and PTSD symptomatology (ICD-11) were assessed with questionnaires. Mediation analyses were performed to investigate possible psychological mediators in the associations between PTSD and pain (intensity and mechanisms).ResultsPatients with PTSD demonstrated increased pain intensity, and psychological distress as well as reduced warmth detection threshold and cPTT compared with patients without PTSD (P<0.05). No significant differences in cPPT, heat pain threshold, temporal summation of pain, and conditioning pain modulation were found. The association between PTSD and pain intensity was mediated by pain catastrophizing, and fear of movement mediated the association with cPTT.DiscussionThe association between PTSD and pain intensity is in accordance with the mutual-maintenance and fear-avoidance models. Future studies should investigate changes in pain intensity and mechanisms after treatment targeting comorbid PTSD in chronic pain patients.

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