I would agree with that, at least for me. I think for me my depression comes from circumstances more than "brain chemistry". I feel very alone, my family is split up, I feel surrounded by others who are having health problems, etc. It seems like for me there's just nothing much to look forward to. It seems like everyone else has it all together with their lives except for me. And recently there are some health concerns for me. I have been perfectly healthy all of my life. I still feel healthy but I've been told to see some specialists because there are some concerns.

That's how I see it with the "brain chemistry" theory.