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Ann Pharmacother. 2003 Dec;37(12):1891-9.

Meta-analysis of placebo rates in major depressive disorder trials.

Author information

1
Department of Pharmacoepidemiology and Pharmacotherapy, Utrecht Institute for Pharmaceutical Sciences, Utrecht, Netherlands.

Abstract

BACKGROUND:

Placebo effects in major depressive disorder (MDD) have received much interest in the medical literature. However, few quantitative analyses have been done in homogeneous populations.

OBJECTIVE:

To determine efficacy rates for placebo in patients with MDD; to quantify the correlation between efficacy and publication year, as well as between placebo and drug response rates.

DESIGN:

Searching MEDLINE (1966-December 2000), EMBASE (1998-February 2001), HealthSTAR (1975-December 2000), and Cochrane (1980-December 2000) databases, randomized, placebo-controlled trials were retrieved including patients with MDD as defined by Diagnostic and Statistical Manual of Mental Disorders, 3rd and 4th editions criteria, Hamilton Rating Scale for Depression score >/=18 or Montgomery-Asberg Depression Rating Scale score >/=16, reporting successes as 50% decreases in scores after 6-8 weeks of treatment. Response rates were summarized using a random effects meta-analysis for per protocol (PP) and intent-to-treat (ITT) results.

RESULTS:

We included 24 of 134 potential studies examining 4459 patients, 1786 on placebo and 2673 on an antidepressant. Placebo response rates were 45.5% (PP) and 26.9% (ITT). Correlations were significant between year and rates (PP rho 0.448, p = 0.042; ITT rho 0.557; p = 0.006), but not for active drugs. Placebo and drug rates were correlated (PP r 0.397, p = 0.020; ITT r 0.539; p = 0.002).

CONCLUSIONS:

These placebo rates confirm those reported previously, but were from a homogeneous population. Although statistically significant, the correlation between drug and placebo rates was lower than others reported. During the study period, placebo rates increased linearly; active drugs did not. Correlations between placebo and drug response rates reflected moderate to strong effect sizes. We suggest that current methodology has been unsuccessful in achieving unbiased double-blind conditions not influenced by extra-trial factors, including time.

PMID:
14632596
DOI:
10.1345/aph.1D172
[Indexed for MEDLINE]

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