It makes some sense: they expended a lot of their youth on the war, then they were defeated [that has to have an impact on morale] and their countries had little in the way of industry left (it having been destroyed [esp in Japan]; Italy pulled out earlier which lessened its damage in this area) which meant fewer decent jobs. — Then there's the post-war inflation to consider: look at how inflation is adversely impacting the middle class's means here and multiply that by an order of magnitude.
If the above gave a more "depressive" social mindset in-general, well, let's just recognize that depression has an impact on the sex-drive.
Plausible. Also wonder if having such huge war losses created a demographic void.