Whether or not this disorder is eventually shown to be primarily or exclusively a variant of "depression" remains to be seen. Meanwhile, this latter state surely deserves greater respect. In Puritan times it was often considered a proper condition for the pilgrim confronting the higher reaches of life and striving to have some worthy impact. Thomas Hardy, in his novels, seems to have had a similar, more noble vision of it.
The point at which people give up in the face of problems is likely to vary with the extent of their engagement in them at all, as well as their psychological capacity then to cope.
Some may collapse more readily, inviting others to label them "unstable" or "inadequate" as implied by Yvette Cooper. Others only falter after striving mightily in life's arena, more so than many of us and beyond the call of duty - a process that may require powerful mental defence mechanisms to be in place. This may render it more likely that, eventually, any breakdown will express itself in physical rather than emotional terms. Such people may then be the most difficult to reach and help psychologically.
Perhaps we can make a start by coming to respect "depression" more in the individual, recognising it as sometimes a rather mature state of mind and, with appropriate help, a potential gateway to further personal growth; "sadder but wiser" and constructively so.
Professor ARTHUR CRISP FRCPsych