Highlights
- •Fear learning deficits in the link between chronic pain and posttraumatic stress disorder (PTSD) is proposed.
- •Subjects with PTSD and healthy controls were included in a fear learning experiment.
- •PTSD subjects with comorbid pain did not show safety learning.
- •Deficits in safety learning may increase fear and, consequently, pain sensation.
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 control subjects 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 nonpainful 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 control subjects, 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 the control group. 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.
Key words
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Article info
Publication history
Published online: September 15, 2016
Accepted:
September 8,
2016
Received in revised form:
August 30,
2016
Received:
March 2,
2016
Footnotes
J.J. and J.E. contributed equally to this work.
This work was supported by the Hermann Klaus Foundation, Zurich, Switzerland; Werner Alfred Selo Foundation, Zurich, Switzerland; and the Kurt and Senta Herrmann Foundation, Zurich, Switzerland.
The authors have no conflicts of interest to declare.
Identification
Copyright
© 2016 by the American Pain Society
