Capsaicin May Be Associated with Prolonged and More Intense Pain Perception in Subjects with PTSD

AUSTIN, TX—Investigators reporting at the American Pain Society's 30th Annual Scientific Meeting shared results of their study regarding musculoskeletal pain in sufferers of post-traumatic stress disorder (PTSD). One of the most common comorbidities of PTSD, a psychiatric disorder that profoundly affects an individual's health and life is chronic pain, specifically, musculoskeletal pain. While underlying mechanisms connecting PTSD and musculoskeletal pain are poorly understood, it is speculated that heightened central processing of incoming stimuli may be involved.

Tobias Moeller-Bertram, MD, MAS, of the University of California, San Diego and the Veterans Administration San Diego Healthcare System, and colleagues, wanted to assess if experimentally induced muscle pain was more intense or prolonged in subjects with PTSD compared with healthy controls. Dr. Moeller-Bertram investigated whether 10 subjects with PTSD experienced more intense or prolonged pain compared with a sample of 11 healthy controls by experimentally inducing muscle pain stimulus. All subjects were male, medication free, and matched for age. Each subject received two consecutive injections of normal saline (10µL, control) and capsaicin (10µL) into their right and left quadriceps muscle, respectively.

Following the injection and every five minutes for a total of 30 minutes, current pain intensity and unpleasantness were rated on a visual analog scale (VAS). Although no significant differences were observed in mean peak pain ratings for both groups, there was a significant difference in the slope of the pain duration curve over the 30 minutes between both groups. The group with PTSD showed higher pain intensity and unpleasantness ratings for much longer than the controls. Final mean pain rating after 30 minutes was 1 out of 10 on the VAS for the control group and 2 out of 10 for the group with PTSD.

The investigators concluded that capsaicin-induced experimental muscle pain causes significantly prolonged and more intense pain sensation in subjects with PTSD compared to healthy controls and felt that further studies are warranted to investigate a possible role of a central sensitized state in the PTSD population.