title: Is there a delay in the antidepressant effect? A meta-analysis.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  METHODS
  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 meta-analysis.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  These results challenge the notion that a delay exists before a true antidepressant effect occurs.
authors.affiliation: Department of Psychiatry and Human Behavior, Brown University School of Medicine, Rhode Island Hospital, Providence, RI 02905, USA. mposternak@lifespan.org
authors.forename: Michael A
authors.initials: MA
authors.lastname: Posternak
authors.forename: Mark
authors.initials: M
authors.lastname: Zimmerman
mesh_terms: D000928:Antidepressive Agents / Q000494:pharmacology* / Q000627:therapeutic use*; D015331:Cohort Studies; D003866:Depressive Disorder / Q000188:drug therapy* / Q000523:psychology*; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D006801:Humans; D015990:Placebo Effect; D010919:Placebos; D011569:Psychiatric Status Rating Scales; D016032:Randomized Controlled Trials as Topic; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D000928:Antidepressive Agents; D010919:Placebos