The difference with depression is that it is not always obvious to yourself, if you are the one being depressed and you are the one trying to spot it, it can be far from immediately apparent. There can be a lot of "silly" things that build up and up, not things that on their own might be considered a problem, and suddenly "snap" something from the outside trivial can lead you wanting it all to end.
However, an atmosphere where it feels safe to admit problems would be a good start.