Ruth Defrin, PhD, and colleagues from Tel-Aviv University in Israel have uncovered new information on the mechanism underlying comorbid post-traumatic stress disorder (PTSD) and chronic pain, according to a study published in The Journal of Pain.1
Their findings suggest that the seemingly paradoxical emotional profile of PTSD (dissociation and anxiety) underlies the paradoxical pain profile of hyposensitivity and hyperresponsiveness to pain, including comorbid chronic pain.
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“This knowledge could help to provide better management of PTSD and chronic pain among individuals in the aftermath of trauma,” the authors write, noting that the dual diagnosis affects 25% to 93% of PTSD patients, and 22% to 49% of those with chronic pain.
In a prior work2, Dr. Defrin and colleagues used somatosensory testing to show that patients with terror– or combat-related PTSD and comorbid chronic pain had a seemingly paradoxical response to painful stimuli. In that study, patients with PTSD exhibited a higher rate and greater intensity of chronic pain than those with anxiety disorder and healthy controls. PTSD was characterized by a unique sensory profile of hyposensitivity to pain, accompanied by hyperreactivity to suprathreshold noxious stimuli.
Building on these discoveries, researchers tested the hypothesis that anxiety, anxiety sensitivity, and pain catastrophizing in PTSD patients are associated with hyperresponsiveness to pain, and that dissociation is in this population correlates with pain hyposensitivity.
Anxiety, pain catastrophizing, and anxiety sensitivity — the fear of anxiety and anxiety-related sensations — are known to be related to pain hyperresponsiveness in chronic pain patients and healthy individuals alike, while dissociation has been correlated with hyposensitivity to pain in patients with borderline personality disorder irrespective of concurrent PTSD. Individuals with chronic pain who do not have PTSD typically exhibit hyperresonsiveness, but typically are hypersensitive, not hyposensitive, to painful stimuli.
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For the study, researchers enrolled 32 patients with combat-related PTSD, and a control group of 43 healthy individuals. Pain thresholds were determined by gradually increasing heat on the dorsal surface of the hand with a thermal stimulator, and by gradually increasing pressure on the dorsal surface of the hand with a pressure algometer.