Patients with posttraumatic stress disorder show reduced pain sensitivity, a pattern that may be related to altered pain processing in the brain, according to a report in the January issue of the Archives of General Psychiatry, one of the JAMA/Archives journals.

Posttraumatic stress disorder (PTSD) is an anxiety disorder that may occur in individuals exposed to a traumatic event. It is characterized by chronic arousal, re-experience of the event, and avoidance of stimuli related to the event, according to background information in the article. To the authors' knowledge, no functional imaging study has explored whether patients with PTSD experience and process pain in a different way than control subjects.

Elbert Geuze, Ph.D., of Central Military Hospital and the Rudolph Magnus Institute of Neuroscience, Utrecht, the Netherlands, and colleagues conducted a study to examine neural correlates of pain processing in patients with PTSD. Twelve male Dutch veterans with PTSD and 12 male veterans without PTSD were recruited and matched for age, region of deployment and year of deployment. The experimental procedure consisted of psychophysical assessment and neuroimaging with functional magnetic resonance imaging (fMRI)--the use of magnetic resonance imaging to learn which regions of the brain are active in a specific function. During fMRI, the patients rated the pain they experienced from fixed and variable temperatures applied to their hands.

"Patients with PTSD rated temperatures in the fixed-temperature assessment as less painful compared with controls," the authors report.

"Before fMRI, patients with PTSD already showed a significant reduction in pain sensitivity," the authors write. "During imaging, patients with PTSD rated a fixed temperature as significantly less painful than control veterans." Patients with PTSD showed altered pain processing in brain areas associated with mood and cognitive pain processing.