St Cross Seminar: What counts as a placebo is relative to a target disorder and therapeutic theory: defending a modified version of Grünbaum’s scheme

There is currently no widely accepted definition of ‘placebos’. Yet debates about the ethics of placebo use (in routine practice or clinical trials) and the magnitude (if any!) of ‘placebo’ effects continue to rage. Even if not formally required, a definition of the ‘placebo’ concept could inform these debates. Grünbaum’s 1981/1986 characterization of the ‘placebo’ has been cited as the best attempt thus far, but has not been widely accepted. Here we argue that criticisms of Grünbaum’s scheme are either exaggerated, unfounded or based on misunderstandings. We propose that, with three modifications, Grünbaum’s scheme can be defended. Grünbaum argues that all interventions can be classified by a therapeutic theory into ‘incidental’ and ‘characteristic’ features. ‘Placebos’, then, are treatments whose characteristic features do not have effects on the target disorder. To Grünbaum whether a treatment counts as a placebo or not is relative to a target disorder, and a therapeutic theory. We modify Grünbaum’s scheme in the following way. First, we add ‘harmful intervention’ and ‘nocebo’ categories; second, we insist that what counts as a ‘placebo’ (or nonplacebo) be relativized to patients; and third, we issue a clarification about the overall classification of an intervention. We argue that our modified version of Grünbaum’s scheme resists published criticisms. Our work warrants a re-examination of current policies of the ethics of placebos in both clinical practice and clinical trials, and a revised empirical estimation of ‘placebo’ effects, both in the context of clinical trials and clinical practice.