Which factors predict placebo response in anxiety disorders and major depression? An analysis of placebo-controlled studies of escitalopram

Background: The placebo response rate has increased in several psychiatric disorders and is a major issue in the design and interpretation of clinical trials. The current investigation attempted to identify potential predictors of placebo response through examination of the placebo-controlled clinical trial database for escitalopram in 3 anxiety disorders and in major depressive disorder (MDD).
Method: Raw data from placebo-controlled studies (conducted from 2002 through the end of 2004) of escitalopram in patients meeting DSM-IV criteria for MDD and anxiety disorders (generalized anxiety disorder [GAD], social anxiety disorder [SAD], panic disorder) were used. Potential predictors examined were type of disorder, location of study, dosing regimen, number of treatment arms, gender of patients, and duration and severity of disorder.
Results: Placebo response (defined as the percent decrease from baseline in the reference scale) was higher in GAD and MDD studies conducted in Europe (p < .0001 and p = .0006, respectively) and was not associated with gender or duration of episode. In GAD, the placebo response rate was higher in a European fixed-dose study, which also had more treatment arms. In SAD and in U.S. specialist-treated MDD, a higher placebo response rate was predicted by decreased baseline disorder severity.
Conclusion: Additional work is needed before definitive recommendations can be made about whether standard exclusion criteria in clinical trials of antidepressants, such as mild severity of illness, maximize medication-to-placebo differences. This analysis in a range of anxiety disorders and MDD suggests that there may be instances in which the predictors of placebo response rate themselves vary across different conditions.

obsessive-compulsive disorder, double-blind, antidepressant, gad, disorders, escitalopram, panic disorder, severity, physicians, generalized anxiety disorder, major depression, social anxiety disorder, clinical-trials, dsm-iv, generalized anxiety, trials comparing placebo, major depressive disorder, placebo, predictors, continuation treatment, placebo-controlled study, drug response, clinical-trial, term treatment, social phobia

1741-1746

http://www.psychiatrist.com/abstracts/abstracts.as...

Stein, Dan J.

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Baldwin, David S.

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Dolberg, Ornah T.

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Despiegel, Nicolas

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Bandelow, Borwin

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2006

Stein, Dan J.

07cf0cbd-837d-49ac-aceb-1c393a2f3e00

Baldwin, David S.

1beaa192-0ef1-4914-897a-3a49fc2ed15e

Dolberg, Ornah T.

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Despiegel, Nicolas

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Bandelow, Borwin

2fbbae21-629e-4d76-b5d0-7dff1282d64d

Stein, Dan J., Baldwin, David S., Dolberg, Ornah T., Despiegel, Nicolas and Bandelow, Borwin (2006) Which factors predict placebo response in anxiety disorders and major depression? An analysis of placebo-controlled studies of escitalopram. The Journal of Clinical Psychiatry, 67 (11), 1741-1746.

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Published date: 2006

Keywords: obsessive-compulsive disorder, double-blind, antidepressant, gad, disorders, escitalopram, panic disorder, severity, physicians, generalized anxiety disorder, major depression, social anxiety disorder, clinical-trials, dsm-iv, generalized anxiety, trials comparing placebo, major depressive disorder, placebo, predictors, continuation treatment, placebo-controlled study, drug response, clinical-trial, term treatment, social phobia