Statistical Question

The nocebo effect

BMJ 2013; 347 doi: http://dx.doi.org/10.1136/bmj.f6130 (Published 11 October 2013)
Cite this as: BMJ 2013;347:f6130

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  1. Philip Sedgwick, reader in medical statistics and medical education
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, London, UK
  1. p.sedgwick{at}sgul.ac.uk

Researchers investigated whether a sham device (validated sham acupuncture needle) and an inert pill exerted a similar placebo effect in patients with persistent arm pain. A single blind randomised controlled trial study design was used. The study was created from the placebo run-in periods for two randomised placebo controlled trials nested within a larger study, the aim of which was to investigate the effectiveness of acupuncture and amitriptyline in relieving arm pain. One trial compared acupuncture (twice a week) with a validated acupuncture sham device for six weeks, whereas the other compared amitriptyline (25 mg once a day) with placebo for eight weeks. Both trials had a placebo run-in period of two weeks. The primary investigation in this study was the comparison of the sham device with placebo pill during the placebo run-in periods.1

Participants were 266 adults with arm pain caused by repetitive use, which had lasted at least three months despite treatment, who scored three or more on a 10 point pain scale. Trial participants were randomised to the acupuncture (n=133) or amitriptyline (n=133) trial. The primary outcome measure was arm pain measured on a 10 point pain scale. At …

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