I don't think anyone can really understand PND or any form of depression unless they have actually suffered from it or someone close to them has done so.
If someone is in agony from back pain you can see that they are suffering but you will not quite know how they feel. However, because the cause is more visible, many people find it easier to empathise.
I do think that depression/other forms of MH problems still have a stigma, especially among older generations. I know people who almost certainly are suffering from depression but will not admit it and will not seek help. A lot of depression goes undiagnosed and it's those who do not seek help at an early stage who are more likely to have a more major breakdown later. You can think you're coping and it can be something quite small and seemingly trivial which is literally 'the straw that broke the camel's back'.
Regarding troisgarcon's phrase 'a touch of', I don't think it's that bonkers actually. There are degrees of depression and these are classified by MH practitioners. My own view is that most people will have a degree of depression sometimes - mainly, but not necessarily, reactive - following big life changes such as death, divorce, birth of a new baby, loss of job etc. I know a birth is generally to be regarded as a joyful event but ther's no getting away from the fact that it is a huge life changing event which can put pressure on relationships, finances etc. And for those who have given up their jobs to be SAMs, there is also the loss of status and financial independence as well as the isolation.
I'm not sure that I have the answers, but I do think that sleep is very important - it's the great healer. Also, getting outside and walking are very good for uplifting spirits. And making a list of things to do and just trying to tick off one or two so that there is some feeling of achievement and progress - if you are at the stage where you can do this. I am gaining the impression that a lot of the above posters coped by doing this. And troisgarcons yes they did cope, many coped very well.
And of course the support of loved ones - if you are lucky enough to have them - is very helpful. And seek support from your GP if you need to. Depression is like any other form of illness to the extent that it comes and goes, gets better or worse, does not discriminate between old and young, rich and poor etc. It is also an extremely nasty illness. Hopefully, threads like this raise awareness.