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Obtained effect size as a function of sample size in approved antidepressants: a real-world illustration in support

Michael Gibertini1, Kari R Nations, John A Whitaker

  • 1INC Research, Austin, Texas 78746, USA. mgibertini@incresearch.com

International Clinical Psychopharmacology
|January 12, 2012
PubMed

Insights

Antidepressant trial success hinges on sample size. Small trials risk misleading results, while adequate sample sizes minimize risks, improving drug development confidence and success rates for new antidepressants.

Area of Science:

  • Psychiatry
  • Clinical Trials
  • Pharmacology

Background:

  • High failure rates in antidepressant clinical trials necessitate understanding factors influencing trial sensitivity.
  • Previous analyses of Food and Drug Administration (FDA) antidepressant trial data have been extended to include recent approvals.

Purpose of the Study:

  • To establish the population effect size (ES) for monoaminergic antidepressants.
  • To demonstrate the relationship between observed ES and sample size in trials of efficacious compounds.

Main Methods:

  • Analysis of an expanded dataset of FDA antidepressant drug registration trials.
  • Examination of the correlation between trial sample size and observed effect size.

Main Results:

  • The overall population effect size for antidepressants is estimated to be approximately 0.30.
  • Variability in observed effect sizes across trials is significantly related to the trial's sample size.

Conclusions:

  • Small sample size trials in antidepressant research are prone to misleading outcomes.
  • Aligning trial sample size with the population effect size minimizes risks of erroneous high or low effect estimations.
  • This study provides concrete evidence to aid drug developers in making informed decisions, enhancing the success probability of future antidepressant trials.

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