Objectives: Posttraumatic stress disorder (PTSD) is prevalent in chronic pain, and associated with increased pain, hyperalgesia and psychological distress. This study aimed to investigate anti-nociceptive and pro-nociceptive 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.
Methods: Cuff algometry was performed on lower legs to assess pressure pain threshold (cPPT), tolerance (cPTT), temporal summation of pain (TSP: increase in pain scores to ten repeated stimulations), and conditioning pain modulation (CPM: increase in cPPT during cuff pain conditioning on the contralateral leg). Warmth detection threshold (WDT) and heat pain threshold (HPT) 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).
Results: Patients with PTSD demonstrated increased pain intensity, and psychological distress as well as reduced WDT and cPTT compared with patients without PTSD (P<0.05). No significant differences in cPPT, HPT, TSP and CPM were found. The association between PTSD and pain intensity was mediated by pain catastrophizing, and fear of movement mediated the association with cPTT.
Discussion: The 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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