Overcoming disagreement: a roadmap for placebo studies

Abstract

In the field of placebo studies residual disagreement about the terminology ‘placebo’ and ‘placebo effect’ still persists. We differentiate between the conceptualization of placebos in clinical trials; and placebo effects understood as a psychobiological phenomenon. With respect to the latter, we argue that a scientific ‘placebo paradigm’ has emerged, indicating that—at least among placebo scientists—there exists relatively stable consensus about how to conceive of placebo effects. We claim that existence of a placebo paradigm does not protect concepts from revision; nonetheless, we argue that scientific progress is dependent on, and guided by relative conceptual stability. Therefore, to mount persuasive arguments for conceptual revision in respect of ‘placebo effects’ we argue, critics either need to defend the claim that a placebo paradigm is not underway, or that there are major scientific failings in respect of it. With these considerations in mind we examine three alternative proposals for conceptual reform: Grünbaum/Howick’s relativity models of placebo concepts; Moerman/Brody’s meaning response; and Nunn/Turner’s proposal for conceptual eliminativism. We derive two conclusions from this evaluation. First, we conclude that no convincing arguments have so far been presented for conceptual overhaul of ‘placebo effects.’ Notwithstanding this analysis, we conclude that refinement of this concept is likely. Second, we agree with Turner and Nunn that the term ‘placebo’ in the context of randomized controlled trials remains a source of confusion for many researchers, risking the design and scientific integrity of clinical findings. Therefore, in these contexts, replacing the term ‘placebo’ with ‘control’ is justified.