Elsevier

The Journal of Pain

Volume 18, Issue 7, July 2017, Pages 835-843
The Journal of Pain

Original Report
Lower Placebo Responses After Long-Term Exposure to Fibromyalgia Pain

https://doi.org/10.1016/j.jpain.2017.02.434Get rights and content
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Highlights

  • Long-term exposure to fibromyalgia was associated with lower placebo analgesia.

  • Subjective report of placebo response correlated with clinical improvements.

  • Placebo responders had lower ratings of depression symptoms at baseline.

Abstract

Knowledge about placebo mechanisms in patients with chronic pain is scarce. Fibromyalgia syndrome (FM) is associated with dysfunctions of central pain inhibition, and because placebo analgesia entails activation of endogenous pain inhibition, we hypothesized that long-term exposure to FM pain would negatively affect placebo responses. In our study we examined the placebo group (n = 37, mean age 45 years) from a 12-week, randomized, double-blind, placebo-controlled trial investigating the effects of milnacipran or placebo. Twenty-two patients were classified as placebo nonresponders and 15 as responders, according to the Patient Global Impression of Change scale. Primary outcome was the change in pressure pain sensitivity from baseline to post-treatment. Secondary outcomes included ratings of clinical pain (visual analog scale), FM effect (Fibromyalgia Impact Questionnaire), and pain drawing. Among placebo responders, longer FM duration was associated with smaller reductions in pressure pain sensitivity (r = .689, P = .004), but not among nonresponders (r = −.348, P = .112). In our study we showed that FM duration influences endogenous pain regulation, because pain levels and placebo-induced analgesia were negatively affected. Our results point to the importance of early FM interventions, because endogenous pain regulation may still be harnessed at that early time. Also, placebo-controlled trials should take FM duration into consideration when interpreting results.

Perspective

This study presents a novel perspective on placebo analgesia, because placebo responses among patients with chronic pain were analyzed. Long-term exposure to fibromyalgia pain was associated with lower placebo analgesia, and the results show the importance of taking pain duration into account when interpreting the results from placebo-controlled trials.

Key words

Placebo analgesia
fibromyalgia
long-term pain
chronic pain
pain inhibition

Cited by (0)

Clinical trial registration EudraCT 2004-004249-16.

This work was supported in part by the pharmaceutical company Pierre Fabre through financing of a placebo-controlled drug intervention study (EudraCT: 2004-004249-16).

The authors have no conflicts of interest to declare.