That number might be optimistic, anti-depressants do not fare well against placebos. This is a good read,
Antidepressants and the Placebo Effect by Irving Kirsch, I'll quote a section but the whole thing is worth reading:
How is it possible that medications with such weak efficacy data were approved by the FDA? The answer lies in an understanding of the approval criteria used by the FDA. The FDA requires two adequately conducted clinical trials showing a significant difference between drug and placebo. But there is a loophole: There is no limit to the number of trials that can be conducted in search of these two significant trials. Trials showing negative results simply do not count. Furthermore, the clinical significance of the findings is not considered. All that matters is that the results are statistically significant.
The most egregious example of the implementation of this criterion is provided by the FDA’s approval of vilazodone in 2011. Seven controlled efficacy trials were conducted. The first five failed to show any significant differences on any measure of depression, and the mean drug-placebo difference in these studies was less than ½ point on the HAM-D, and in two of the three trials, the direction of the difference actually favored the placebo. The company ran two more studies and managed to obtain small but significant drug-placebo differences (1.70 points). The mean drug-placebo difference across the seven studies was 1.01 HAM-D points. This was sufficient for the FDA to grant approval, and the information approved by the FDA for informing doctors and patients reads, “The efficacy of VIIBRYD was established in two 8-week, randomized, double-blind, placebo-controlled trials.” No mention is made of the five failed trials that preceded the two successful ones.