The placebo drug reactions from controlled trials were studied for the first time systematically for efficacy and the safety in drug data pooled from randomized, placebo-controlled, multicentre studies. Results: The efficacy of placebo on clinical symptoms and outcome varied between the therapeutic indications. However, no placebo effects on laboratory values, as e.g. blood glucose or Hb1c in diabetics, were noted. The frequency and type of placebo-induced adverse reactions also varied between indication groups. The placebo side effect profile was largely similar to the side effect profile of the active treatment. The mechanisms of placebo effects are manyfold and varied (e.g. endorphin release, conditioning), much lacks explanation. Conclusion: Since the prescription of non-evidence based medicines (= pseudoplacebos) may clearly also result in serious adverse effects, such practice may not only be non-beneficial but may even be harmful. In clinical research, the judicious use of placebo remains essential to establish the efficacy and safety, safeguarding that patients receiving placebo will not be subject to harm and are fully informed.
placebo efficacy adverse drug reactions clinical trials ethics Declaration of Helsinki