Placebo Response in Clinical Trials with Schizophrenia Patients

Bruce J. Kinon; Alison J. Potts; Susan B. Watson


Curr Opin Psychiatry. 2011;24(2):107-113. 

In This Article

Abstract and Introduction


Purpose of review The magnitude of placebo response is an important factor in the outcome of clinical trials, in that excessive placebo response can obscure true drug–placebo differences. There is ample evidence of the impact of elevated placebo response in trials of major depression, but less intensive research has been done in the area of schizophrenia. We present a current review of placebo response in clinical trials of schizophrenia.
Recent findings The existing evidence suggests that placebo response in schizophrenia trials may be similar in magnitude, quality, and impact to that observed in depression trials, and has similarly increased over the past several years. We discuss factors influencing excessive placebo response during the conduct of clinical trials and how they may be managed to help minimize placebo response.
Summary There does not appear to be any single major factor contributing to the high levels of placebo response in schizophrenia clinical trials; therefore, a multipronged approach to minimizing excessive placebo response or its impact is recommended.


Excessive placebo response is an important factor in the failure rate of psychiatric medications in clinical trials, and it appears to be increasing over time.[1,2,3••,4] Failures to demonstrate drug–placebo differences where true differences exist could cause sponsors to terminate drug development programs prematurely, thus preventing patient access to effective treatments. Finding drugs to be ineffective at a late stage (i.e., during phase III) is extremely costly, so it is in the interest of researchers to minimize or eliminate artifactual causes of drug failure, such as inadequate study design, data quality issues, or excessive placebo response. The current review focuses on anomalous placebo response in clinical trials of schizophrenia, seeking to understand the contributing factors and also to suggest ways of possibly minimizing placebo response, thus making true drug–placebo differences more salient.