The reporting if these studies is complete nonsense!
They may be twice as effective as placebo - but that can mean that placebo is 1% effective and the drug is 2% effective. In fact the study doesn't rate the anti-depressants by clinical effectiveness, they are rated by a statistical term - the Odds Ratio. (If you like statistics here is an explanation of the Odds Ratio https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2938757/)
The studies also don't look at the rate of side effects (which can include anxiety, depression and suicidal thoughts!) - they just look at drop out rates.
A better study would be to compare anti-depressants against going for a good walk or talking to friends.These have no bad effects and proven benefits. For .nutritional approaches to help depression see the video below
However big pharmaceutical companies don't make any money from you going for a good walk or facing up to your fears and worries - so these comparisons studies will never get funded.
Anti-depressants: Major study finds they work - BBC News http://www.bbc.co.uk/news/health-43143889
Original Lancet paper http://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(17)32802-7.pdf