There is an emerging theory that treatment-resistant depression was not as prevalent before the advent of SSRIs.

“somebody who's highly informed in the in the landscape of of pharmaceutical treatments for um psychiatric challenges has told me that there's an emerging Theory among psychiatrists as kind of a collective emerging theory that um one of the reasons why nowadays you hear about so-called treatment resistant depression but you did not hear about so-called treatment resistant depression prior to the Advent of ssris is that there's a growing body of thought in the psychiatric Community the ssris May over time as you're pointing out deplete the very neural systems that subserve enhanced mood”