Initial severity and antidepressant benefits: a meta-analysis of data submitted to the Food and Drug Administration.
Level 1 - systematic review of randomized trials
Meta-analysis of randomized controlled trials submitted to the FDA
PubMed 18303940 · doi:10.1371/journal.pmed.0050045
What was done
The authors conducted a meta-analysis of clinical trial data submitted to the US Food and Drug Administration (FDA) for the licensing of four new-generation antidepressants for which full datasets were available. Using meta-analytic and meta-regression techniques, they evaluated linear and quadratic relationships between baseline depression severity and symptom improvement in drug and placebo groups, as well as drug-placebo difference scores.
What was found
The abstract reports no numerical values (such as sample sizes, trial counts, effect sizes, or confidence intervals). Drug-placebo differences increased as a function of initial depression severity, with virtually no difference at moderate baseline levels and a relatively small difference for very severe depression. Conventional criteria for clinical significance were reached only for patients at the upper end of the very severe depression category. Meta-regression indicated this relationship was driven by a strong negative linear decrease in placebo response as baseline severity increased, rather than increased drug responsiveness.
Why it matters
This study indicates that the apparent efficacy advantage of new-generation antidepressants in severe depression is largely driven by a reduced placebo response rather than enhanced drug action, challenging their clinical benefit in mild-to-moderate depression.
Limits
The abstract omits critical quantitative details, including the number of included trials, participant sample size, specific drug names, and numerical effect sizes. The dataset is limited to trials submitted to the FDA for four specific antidepressants and may not generalize to other classes, long-term outcomes, or broader clinical settings.
Cited by
- supports In pivotal clinical trials for oral antidepressants such as Prozac, the difference between active drug and placebo was only 2 to 3 points on a 60-point scale, matching the inter-rater reliability margin of error.