Initial Severity and Antidepressant Benefits: A Meta-Analysis of Data Submitted to the FDA

Here's the actual study that an earlier referred to earlier:

Using complete datasets (including unpublished data) and a substantially larger dataset of this type than has been previously reported, we find that the overall effect of new-generation antidepressant medications is below recommended criteria for clinical significance. We also find that efficacy reaches clinical significance only in trials involving the most extremely depressed patients, and that this pattern is due to a decrease in the response to placebo rather than an increase in the response to medication.