This study tested the experimental placebo effect in a group of chronic pain patients. Forty-eight patients having chronic back pain participated in a randomized clinical trial that tested the efficacy of a sham opioid solution (NaCl) compared with an alleged neutral, completely inactive solution (NaCl). We shaped the placebo effect by 2 interventions: verbal instruction and conditioning. The patients were either told that the “solution reduces pain and improves physical capacity” or the “solution is neutral, a placebo.” Half of each group was additionally conditioned (coupling solution with reduced experimental pain), yielding 4 subgroups with 12 participants each. Outcome measures were as follows: the patients' clinical back pain ratings and acute pain ratings (both examined by numerical rating scale 0-10) and self-rated functional capacity (0%-100%; time required for the exercise). Expected pain relief before and after solution intake was also assessed. The inactive solution (NaCl), when presented as an effective treatment (sham “opioid” solution), induced placebo analgesia as evident in lower ratings of the patients' clinical back pain (F(3.12,144.21) = 25.05, P < 0.001), acute pain ratings (F(1.99,87.40) = 18.12, P < 0.01), and time needed to complete a series of daily activities exercises (F(1,44) = 8.51, P < 0.01) as well as increased functional capacity (F(1,44.00) = 19.42, P < 0.001). The 2 manipulations (instruction and conditioning) changed pain expectations, and they were maintained in both sham opioid groups. The results suggest that it may be clinically useful to explicitly integrate placebo analgesia responses into pain management.
Supplemental Digital Content is Available in the Text.Placebos associated with the instruction “highly effective opioid” and additional conditioning reduce experimental and clinical pain and improve physical capacity of chronic back pain patients.
aDepartment of Anesthesiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
bDepartment of Spinal Surgery, Schön Klink Hamburg Eilbek, Hamburg, Germany
cDepartment of Orthopedics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
dDepartment of Clinical and Cognitive Neuroscience, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Heidelberg, Germany
eDepartment of Psychology, University of Mannheim, Mannheim, Germany
Corresponding author. Address: Department of Anesthesiology, Pain Therapy and Pain Psychology, Center for Anesthesiology and Intensive Care Medicine, University Medical Center Hamburg-Eppendorf (UKE), Martinistraße 52, 20246 Hamburg, Germany. E-mail address: email@example.com. Tel.: +49 40 7410 52837; fax: +49 40 7410 44963 (R. Klinger).
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Received December 23, 2016
Received in revised form May 24, 2017
Accepted May 30, 2017