BMJ  2005;330:45 (1 January), doi:10.1136/bmj.330.7481.45-b

Letter

Placebos in medicine

Is placebo analgesia always in the mind?

EDITOR—Spiegel discussed placebos in medicine.¹ A study published in the 1979 edition of Advances in Pain Research and Therapy offered a tantalising glimpse of a possible mechanism for placebo analgesia.²

A hundred or so patients who had their wisdom teeth extracted were assigned (random double blind) to a fixed dose of an opiate or the same volume of saline for postoperative analgesia. The difference in the proportion of patients in the opiate versus the saline group who expressed satisfactory pain relief did not reach significance. Placebo analgesia worked in a case of organic pain, postoperative pain.

The researchers then broke the code after collecting analgesia data and then randomised (again double blind) the saline responders to saline or a dose of naloxone. All the saline responders who received naloxone complained of their pain again. This indicates that endogenous analgesic systems of encephalins or endorphins might be important.

So is placebo analgesia all in the mind? Or does the mind work through known neuropharmacological pathways?

Department of Anaesthesia, Yan Chai Hospital, Tsuen Wan, New Territories, Hong Kong SAR, China lovpetay{at}netvigator.com

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Competing interests: None declared.

References

1. Spiegel D. Placebos in medicine. BMJ 2004;329: 927-8. (23 October.)[Free Full Text]
2. Levine JD, Gordon NC, Fields HL. The role of endorphins in placebo analgesia. In: Bonica JJ, ed. Advances in pain research and therapy. Vol.3. New York: Raven Press, 1979: 547-51.

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