Initial depression severity and response to antidepressants v. placebo: patient-level data analysis from 34 randomised controlled trials.

Several often-cited meta-analyses have reported that the efficacy of antidepressant medications depends on the severity of depression. They found that drug-placebo differences increased as a function of initial severity, which was attributed to decreased responsiveness to placebo among patients with severe depression rather than to increased responsiveness to medication. We retested this using patient-level data and also undertaking a meta-analysis of trial-level data from 34 randomised placebo controlled trials (n = 10 737) from the NEWMEDS registry. Although our trial-level data support prevous findings, patient-level data did not show any significant effect of initial depression severity on drug v. placebo difference.