In the 1950s it was assumed that this was a story that mainly affects mothers. They were housewives and were alone in their own home during the day because the children - the term came from the USA - went to college. This affected a number of women in a similar way. And then a clever psychologist said: 'The nest is actually not empty, the woman is empty.' - which then has no other tasks at all and has now lost its right to exist a bit and is therefore sad.