I think this is the paper in question?

https://osf.io/preprints/psyarxiv/wk4et_v3

Clinical trials of antidepressants are weird because they're usually short-term (6-12 weeks), whereas practical use of antidepressants usually lasts years. I personally suspect that short-term trials show an exaggerated placebo effect, because the novelty doesn't have time to wear off.