Discussing mental illness is praiseworthy — it’s not washing dirty linen
In the case of depression, nobody is to blame, and certainly not the person suffering from it. Marian Keyes should be praised and encouraged for her willingness to share the fact of her depression with the public.
Only when enough people do this can depression (and any other mental illness) be seen as something that happens: it happens to all sorts of people from all walks of life through no fault of their own.