Deception in Research on the Placebo Effect

T he placebo effect is a fascinating yet puzzling phenomenon, which has challenged investigators over the past 50 years. Recently, it has been defi ned as the " positive physiological or psychological changes associated with the use of inert medications, sham procedures, or therapeutic symbols within a healthcare encounter " [1]. Increasing scientifi c inquiry has been aimed at elucidating the mechanisms responsible for placebo effects and determining how inert interventions can lead to positive changes in patients [1,2]. The majority of placebo mechanism research has been done within the context of experimental and clinical pain. Patients' expectations for improvement, also referred to as " response expectancies, " are thought to be one of the central mechanisms responsible for placebo effects [3–5]. Brain imaging techniques are being used to explore both the neurophysiological correlates of these expectations and the mechanisms underlying placebo effects in a variety of contexts, including pain relief in healthy participants, relief of symptoms of depression, and motor functioning in patients with Parkinson disease [6–8]. Understanding these mechanisms is an important step in harnessing the placebo effect in patient care. In the words of a National Institutes of Health request for applications, " understanding how to enhance the therapeutic benefi ts of placebo effect in clinical practice has the potential to signifi cantly improve healthcare " [9]. Toward that end, the National Institutes of Health invited submissions for systematic studies aimed at discerning the psychosocial factors (including expectancy) in the patient–clinician relationship and/or in the health-care environment that can potentiate healing. A common feature of research investigating the placebo effect is deception of research participants about the nature of the research. This use of deception is considered necessary to understanding the placebo effect, but has received little systematic ethical attention. In this article, we examine ethical issues relating to deception in research on the placebo effect, with a particular focus on experiments involving patients in clinical settings. We propose a method of informing participants about the use of deception that can reconcile the scientifi c need for deceptive research designs with the ethical requirements for clinical research. Response expectancy is seen to be a major driving force behind the placebo effect. Therefore, a common (and some would argue, necessary) feature of research aimed at elucidating placebo mechanisms is the use of deception in experimental manipulation of participants' expectations (e.g., about whether or not they will receive a …