Placebo response in generalized anxiety: its effect on the outcome of clinical trials

The development of new treatments for generalized anxiety disorder increasingly has been sabotaged by a high placebo-response rate. As a consequence, and in contrast to the surge of approvals for new antidepressants, only one new anxiolytic has been approved by the U.S. Food and Drug Administration in the past 15 years. This article presents a brief review of factors that contribute to the placebo response in treatment studies of generalized anxiety. Since anxiety is a normal emotion that is sensitive to a variety of life stresses, it is particularly difficult to achieve the primary goal of a clinical trial, which is to extract the "signal" of a drug effect from the "noise" of background fluctuations in symptoms. Data from the published literature and from the authors' research unit concerning placebo-response trends are reviewed.