I'm horning in here uninvited, but I just want to say that your insight seems to be very accurate, and not something the ordinary physician nay completely miss. Twice in my life I had depressive episodes that just floored me, but they were both occasions when I knew I was not right with God, and I had to repent big time. If you look at this closely, turning from habitual sin is a withdrawal process, in psychological jargon.
Getting right with God in the end makes you feel much better! That's the change going on that you mentioned. Satan just hates to lose control over you when you reach out to Jesus in full faith, and He reaches out and pulls you out of the miry pit, and puts a new song in you.
You expressed my thoughts much better than I did. LOL. First and foremost, anyone with severe clinical depression should immediately seek help. That said, our society wants everyone to be happy and that is not what God intended. There are always going to be periods in people’s lives where they are confused and unhappy, it is now called depression. I truly believe these are moments when we are forced to look inward, become closer to God, and learn more about ourselves, where we have been and where we are going. Instead, doctors throw anti-depressants at us and that becomes our temporary salvation, therefore one’s journey ends. We should embrace these moments of our lives, not fear them.