That’s just it! When the brain can’t perceive the cause of its distress it makes up reasons. The sky’s falling and there’s nothing to be done about it. No way out.
Even if by luck (and it’s often just luck) you get prescribed the right antidepressant, it takes a month or more to to kick in. I can recall reading a New Yorker magazine in the waiting room of my medical doctor when gradually the dark cloud began to lift. Things that I considered impossible became somehow possible. I could see a way out of my dilemma. The was a mild euphoria knowing there could be a future.
The problem is that brain chemistry is as yet a relatively inexact science. Trial and error and patience are required and patience can be deadly.