Altered pain perception and fear-learning deficits in subjects with posttraumatic stress disorder

Abstract There is growing evidence that fear-learning abnormalities are involved in the development of posttraumatic stress disorder (PTSD) and chronic pain. More than 50% of PTSD patients suffer from chronic pain. This study aimed to examine the role of fear-learning deficits in the link between pain perception and PTSD. We included 19 subjects with PTSD and 21 age- and sex-matched healthy controls in a fear-conditioning experiment. The conditioned stimulus (CS) consisted of visual signs flashed upon a screen in front of each subject. The unconditioned stimulus was either a low or high temperature impulse delivered through a thermal contact thermode on the subjects hand. A designation of ‘CS-‘ was assigned to CS always followed by non-painful low-temperature stimuli; a designation of ‘CS+’ was given to CS that were randomly followed by either a low or a more-painful high temperature. Skin conductance was used as a physiological marker of fear. In healthy controls, CS+ induced more fear than CS-, and a low-temperature stimulus induced less subjective pain after CS- than after CS+. PTSD subjects failed to demonstrate such adaptive conditioning. Fear ratings after CS presentation were significantly higher in the PTSD group than in controls. There were significant interaction effects between group and the type of CS on fear and pain ratings. Fear-learning deficits are a potentially-promising, specific psychopathological factor in altered pain perception associated with PTSD. Deficits in safety learning may increase fear and, consequently, pain sensations. These findings may contribute to elucidating the pathogenesis behind the highly-prevalent comorbidity that exists between PTSD and pain disorders, and to developing new treatments. Perspective This study provides new insights into the pathogenesis of chronic pain in patients with PTSD. The findings may help to develop new treatment strategies for this highly-prevalent comorbidity in PTSD.