Is There a Delay in the Antidepressant Effect? A Meta-Analysis
J Clin Psychiatry 2005;66(2):148-158
© Copyright 2014 Physicians Postgraduate Press, Inc.
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Objectives: It has long been thought that there
is a delay of several weeks before a true antidepressant effect
occurs, although this theory has increasingly come into question.
The goals of this meta-analysis were to determine whether
significant drug-placebo separation occurs during the first 2
weeks of treatment and to ascertain whether the timing of
response to antidepressant medication and placebo is distinct.
Data Sources: Seventy-six double-blind,
placebo-controlled trials conducted between 1981 and 2000,
included in a recently published meta-analysis that evaluated
placebo response rates in depressed outpatients, were reviewed.
In addition, each issue of 6 psychiatric journals from January
1992 through December 2001 was reviewed.
Study Selection: Forty-seven studies that
evaluated antidepressant medications with established efficacy,
performed weekly or biweekly (every other week) evaluations, and
presented the time course of improvement as measured by the
Hamilton Rating Scale for Depression were included in our
Data Synthesis: The time course of improvement
on active medication and placebo was nearly identical, as 60.2%
and 61.6% of the improvement that occurred on active medication
and placebo, respectively, took place during the first 2 weeks of
treatment. Drug-placebo differences were not only present but
were most pronounced during the first 2 weeks of treatment and
diminished in a stepwise fashion thereafter. A series of
subanalyses confirmed that this early drug-placebo separation was
clinically observable and represented a true drug effect.
Conclusion: These results challenge the notion
that a delay exists before a true antidepressant effect occurs.