Although this study by Kaptchuk et al is fascinating and undoubtedly advances our knowledge of placebo effects, the concept of open placebo is not quite as novel as Kaptchuk et al believe, as I think their literature search may have missed a highly relevant paper. Amanzio and Benedetti also used open placebos in their trial of analgesia [1]. They found that administration of open placebo to patients who had been conditioned by treatment with either morphine or ketorolac produced analgesia, and fascinatingly, the placebo effect in patients conditioned by morphine was reversible with naloxone, whereas that in patients conditioned by ketorolac wasn't.
References:
1. Amanzio M, Benedetti B. Neuropharmacological Dissection of Placebo Analgesia: Expectation-Activated Opioid Systems versus Conditioning-Activated Specific Subsystems. The Journal of Neuroscience, January 1, 1999, 19(1):484-494
