I like this language, "messes with your sensors." Depression is a disease within the brain, and naturally it's difficult to observe a system from within that system - especially when those observational tools are affected by the system itself.
So it's really hard to know you have depression and take the steps to treat it, when you have depression.
Freud said that the purpose of therapy was to replace neurotic misery with ordinary human unhappiness. Some Californians find that a bit of a downer, but it's true, and we can do something about unhappiness.
Hormones are well known to interact with the stress system and exacerbate depression.
You make a good point about depression itself causing issues with (for example) your job, making it difficult to know what is the source of the problem. I think the best that people can do in this situation is to take a break from work, and think carefully about what they really want from life.
And with depression (or anxiety), this isn't so easy. It gets difficult to see opportunities and easier to blame yourself, thinking, "I'm lucky to have this crappy job and that they put up with me". It can make your job seem crappy, even when it isn't.
I get to see the way the chemicals affect my brain once a month. Once a month, I think I'm going to lose my job. That people dislike me. That people are suddenly treating me harshly and I must have done something wrong. I consider changing jobs.
This is like this even when I enjoy my work and actually like the folks I'm surrounded with. It doesn't stop with work, but is a handy example.
I likely should be on anti-depressants half the month - if you've not figured it out, I'm female and this is entirely hormone-related. Instead, I've adjusted life. Once I realize what is going on, I can relax some on the temporary nature of it all. Sometimes it works better than others.
The thing is when depression hits, for me, it is much like this. All the freaking time. Work becomes a relief from home, home becomes a relief from work, sleep a relief from it all. I literally don't have the capacity to sort out which things in life to change or what to do next. I get stuck.
This is why it is a long-term preventative measure. Gotta catch this stuff before the darkness sets in and messes with your sensors.