Sounds plausible. A person can get worn down.

As for myself, I first became clinically depressed all those years ago when it became obvious my other issues were overwhelming and intractable. I don't get panic attacks or have the usual physical symptoms as such. I'm avoidant. When my avoidance wins and I am perpetually denied the life that others experience, I become severely depressed. When I make inroads against it and have some measure of success, my depression lifts. It isn't complicated or abstract. It's just horrifically painful and hard -- especially when the depression feeds back into it. That's why I have to take tiny steps and build myself up.