Many people who believe they are just being struck randomly by depression are simply not aware of the reasons they are feeling depressed. That doesn't mean there aren't emotional/psychological reasons for what they're experiencing---only that they don't see those things as the cause.

For the first decade or so after being diagnosed with depression I believed it could only be explained by brain chemistry or something like that. Only later in life when I learned more about healthy relationships and what does and doesn't work for me emotionally did I realize that my depression was an obvious reaction to the dysfunctional environment I was raised in.

My ignorance of the non-chemical causes of my depression made me feel I was "just struck by it". But there really was a cause in my environment. I believe this is true for many other people as well.

Depression and anxiety in particular I think are better explained as a mismatch between human adaptation and current human environment. They are signals that things are unsafe/insecure. It seems to me more wise to focus on improving our environment than on constantly blaming the brain, whether through the serotonin hypothesis or this new neuroconnectivity approach.

I also didn't realize how much I was shaped by my awful upbringing. I just thought I'd get away and that I was a rational person and everything would be all right.

Maybe a distinction should be made between people who are aware of their source of depression and people who are not? Like it makes sense to be depressed if you're living in abject poverty. People can point to it and say I know why I'm depressed. That seems different from someone who lives in a secure environment, feels valued, has meaningful relationships, engages in rewarding work, etc. All these things that should lead to a happy life but this person still feels bad. That's definitely a different thing, no?

During times when I lack rewarding work and relationships, I get diagnosed with clinical depression. During times when I have those things, I feel great. I don't think everybody will ever agree on the distinction.

They might have a good life now, but experienced bad things in their first 6 years - left alone too long, suppressed by relatives, outcast at kindergarten... We are so formable in those years, and dents are easy to be made that don't go away all by themself.

Or, they might have what looks like a good life to outsiders - eg super-rich celebrities with lifestyles idealised by the media - but actually living it is hell.

But I still strongly agree with your point. My strongest influence on this stuff is The Biology of Belief by Bruce Lipton, who explains how it all works on a cellular and genetic level.