A recent meta-analysis of the most commonly prescribed antidepressant drugs raises some very important questions for science-based medicine. The study: Initial Severity and Antidepressant Benefits: A Meta-Analysis of Data Submitted to the Food and Drug Administration, was conducted by Irving Kirsch and colleagues, who reviewed clinical trials of six antidepressants (fluoxetine, venlafaxine, nefazodone, paroxetine, sertraline, and citalopram). They looked at all studies submitted to the FDA prior to approval, whether published or unpublished. They found:
Drug–placebo differences in antidepressant efficacy increase as a function of baseline severity, but are relatively small even for severely depressed patients. The relationship between initial severity and antidepressant efficacy is attributable to decreased responsiveness to placebo among very severely depressed patients, rather than to increased responsiveness to medication.
The press has largely reported this study as showing that “antidepressants don’t work” but the full story is more complex. This analysis certainly has important implications for how we should view the body of evidence for these antidepressants. It also illuminates the possible role of publication bias in the body of scientific literature – something that has far ranging implications for science-based medicine.