Mindfulness-Based Analgesia or Placebo Effect? The Development and Evaluation of a Sham Mindfulness Intervention for Acute Experimental Pain

摘要

Objective Meta-analyses indicate that mindfulness meditation is efficacious for chronic and acute pain, but most available studies lack active control comparisons. This raises the possibility that placebo-related processes may account, at least in part, for mindfulness effects. The objective of this study was to develop a closely matched sham mindfulness condition to establish whether placebo effects contribute to mindfulness-based interventions for pain. Methods We developed and validated a closely matched sham mindfulness intervention then compared it with 6 x 20-minute sessions of focused-attention mindfulness and a no-treatment condition in 93 healthy volunteers undergoing acute experimental heat pain. Results The sham mindfulness intervention produced equivalent credibility ratings and expectations of improvement as the mindfulness intervention but did not influence mindfulness-related processes. In contrast, mindfulness increased "observing" relative to no treatment but not sham. Mindfulness (F(1,88) = 7.06, p = .009, eta(2)(p) = 0.07) and sham (F(1,88) = 6.47, p = .012, eta(2)(p) = 0.07) moderately increased pain tolerance relative to no treatment, with no difference between mindfulness and sham (F(1,88) = 0.01, p = .92, eta(2)(p) < 0.001). No differences were found for pain threshold. Similarly, neither mindfulness nor sham reduced pain intensity or unpleasantness relative to no treatment, although mindfulness reduced pain unpleasantness relative to sham (F(1,88) = 5.03, p = .027, eta(2)(p) = 0.05). Conclusions These results suggest that placebo effects contribute to changes in pain tolerance after mindfulness training, with limited evidence of specific effects of mindfulness training on pain unpleasantness relative to sham, but not no treatment. To disentangle the specific analgesic effects of mindfulness from placebo-related processes, future research should prioritize developing and incorporating closely matched sham conditions.