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Review: placebo is better than no treatment for subjective continuous outcomes and for treatment of pain

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 QUESTIONS: In patients with various clinical conditions, what is the clinical effect of placebo as a treatment for disease? Does the effect differ for subjective and objective outcomes?

Data sources

Trials published before the end of 1998 were identified by searching Medline, EMBASE/Excerpta Medica, PsycLIT, Biological Abstracts, and the Cochrane Controlled Trials Register. Reference lists were reviewed and experts were contacted.

Study selection

Studies were selected if patients were randomly allocated to a placebo group or an untreated group. Exclusion criteria were unconcealed randomisation, a sample of paid or healthy volunteers, non-blinding of assessors of objective outcomes, a > 50% dropout rate, or if the alleged placebo had a clinical effect not associated with the treatment ritual alone.

Data extraction

The primary outcome was that defined by the trial author or, if not defined, the most clinically relevant outcome.

Main results

114 trials were included. The typical …

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  • Source of funding: no external funding.

    For correspondence: Dr A Hróbjartsson, Department of Medical Philosophy and Clinical Theory, University of Copenhagen, Panum Institute, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark. FAX +45 354 570 07.

  • Abstract and commentary also appear in Evidence-Based Mental Health.