Placebo response in asthma: A robust and objective phenomenon

BackgroundPlacebos are hypothesized to exert positive effects on medical conditions by enhancing patient expectancies. Recent reviews suggest that placebo benefits are restricted to subjective responses, like pain, but might be ineffective for objective physiologic outcomes. Nevertheless, mind-body links and placebo responsivity in asthma are widely believed to exist.ObjectiveWe carried out a randomized, double-blind investigation to (1) determine whether placebo can suppress airway hyperreactivity in asthmatic subjects, (2) quantify the placebo effect, (3) identify predictors of the placebo response, and (4) determine whether physician interventions modify the placebo response.MethodsIn a double-blind, crossover design investigation, 55 subjects with mild intermittent and persistent asthma with stable airway hyperreactivity were randomized to placebo or salmeterol before serial methacholine challenges. Subjects were additionally randomized to physician interactions that communicated either positive or neutral expectancies regarding drug effect.ResultsPlacebo bronchodilator administration significantly reduced bronchial hyperreactivity compared with baseline (the calculated concentration of methacholine required to induce a 20% decrease in FEV1 nearly doubled); 18% of subjects were placebo responders by using conservative definitions. Experimental manipulation of physician behavior altered perceptions of the physician but not the magnitude or frequency of the placebo response.ConclusionsObjective placebo effects exist in asthma. These responses are of significant magnitude and likely to be meaningful clinically. The placebo response was not modulated by alterations in physician behavior in this study.Clinical implicationsThe placebo response in patients with asthma is important in understanding the limitations of clinical research studies and in maximizing safe and effective therapies. This article confirms the existence of a strong placebo response in an objective and clinically relevant measure of disease activity.