LAUSR

For nearly as long as the term has existed “placebo” has been a source of debate and disagreement. Scientists and philosophers have been active contributors to the protracted dialog about how best to define the term leading one prominent health researcher to argue that there appears to be “currently no widely accepted definition of placebo” (1). Meanwhile, new theoretical models aimed at resolving conceptual quagmires—once and for all [e.g., (1, 2)]—often seem to confound rather than crack the problem by inviting further questions (3, 4). If discussion about how to conceive placebo terminology seems to “rage” within the sphere of biomedicine (1) when it comes to the domain of psychotherapy conceptual entanglements appear even more complicated. Here the toand-fro of debate has spanned the decades though been episodic rather than ongoing [e.g., (5–7)] and lately the debate has re-emerged [see: (8–11)]. Reviewing the recent contributions to this discussion, I argue that are indeed stable definitions for the terms placebo and placebo effect within the science of placebo studies. Furthermore, I argue that it is justified to use these definitions as a starting point for appraising conceptual disagreement, including the (apparently) contentious translation of these terms to psychotherapy. Exploring two provocative yet divergent claims about the relationship between placebo and psychological treatments (9, 10) I conclude that disagreement arises when researchers employ definitions of placebo that are disengaged from implicit scientific usage. Discussion about conceptual or definitional matters in science may appear to be esoterica, however definitions are important. How we understand placebo concepts carries subtle but significant methodological significant methodological implications for clinical trials as well as for ethical practice in the delivery of care (4, 12, 13). Therefore, gaining clarity about the argumentation within disputes over concepts is not trivial—rather, it might even be viewed as a major priority for the field of placebo research. In this Mini Review I focus on two of the most prominent recent claims about the relationship between placebo concepts and psychotherapy proposed by leading scholars (9–11). I argue that appearances to the contrary, the resultant conceptual quagmire is avoidable, and suggest how and why definitions of placebo and placebo effects have become muddled within the context of psychotherapy. However, to highlight why disagreement arises it is imperative to identify unambiguous definitions for the terms “placebo” and “placebo effect.” Fortunately, in this regard, the insights of philosopher of science Thomas Kuhn are instructive (14).