There's nothing 'new' or 'fashionable' about Depression. It's just that an earlier generation kept quiet about such things and soldiered on, because they knew that any admission of mental illness could lead to them being bunged in an Asylum and quite possibly kept in there for life. There was also a huge social stigma against any kind of mental illness - people were afraid of it, and to a large extent still are.
What damage was done to society and individuals by non-acknowledged depressives 'soldiering on' we shall never know. But it's hardly likely to have boosted Britain's productivity or general health.
Many depressives end up topping themselves. Yes, we all get 'down' at times, but comparing that to clinical depression is like comparing a minor cold to pneumonia. That is to say, there is no comparison at all. And at least with pneumonia there are proven and certain cures that work for everyone. For depression this is not true.