How do you know it was the SSRI?

To cherry-pick a quote from a review of SSRI studies:

>the magnitude of symptom reduction was about 40% with antidepressants and about 30% with placebo.

That tells me that antidepressants have some effectiveness, but placebos work shockingly well. You can give someone a sugar pill with no medical properties whatsoever, and a good portion of people will recover, likely crediting the pill for their recovery.