The simple answer is "yes" anyone can become clinically depressed.
I am no expert on the subject by any means but as I said previously, I have seen it at first hand, up close and personal.
And it's frightening.
There are differing types and degrees of clinical depression and I can only really talk about the one form that I have had experience of.
I had it explained to me by a doctor as "the physical residue of coping with elevated levels of stress for a sustained period."
When you're going through some shit, your body has in-built mechanisms for coping. It regulates its own chemical balance and makes tiny adjustments to keep you on an even keel.
Depression can occur either when finally it all gets too much and your body can't physically cope any more and things start to break down or (and this is the interesting one for me) all the shit has stopped and things are starting to look up.
And this second manifestation is the one that confuses people - the "What's he got to be depressed about?" thing that you hear so often.
I can't remember exactly what he said but it went along the lines of, your body has become so used to coping with the stress for so long, it becomes locked-in to that way of operating and when the stress is removed, it carries on fiddling with the chemical balance in the brain and this causes the problems.
And the frightening thing is, you may not even have been aware that you were under stress in the first place, so when Depression strikes, you haven't a clue what's going on and it floors you.
You think you're losing your mind and you don't know why.
So in summary, yes it's real and yes it can strike anybody.