Well, no you can't because it seems a lot of people with really good life are just struck by it.
Although I believe the environment (physical, emotional, relational [edit: in recovery or/and prevention]) plays a huge role there still seems to be something extra going on.
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.
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.