Like, is it just total darkness or, the opposite? Is it easier for them to fall asleep given that there’s no light to distract them whilst trying to nod off?
I feel like an absolute ass for asking these questions, and I’m honestly not trying to hurt anyone’s feelings or anything.
For your latter point, does it happen for people born blind or those who have accidents that result in loss of sight?
It appears it can affect both groups, according to this wiki entry:
https://en.m.wikipedia.org/wiki/Non-24-hour_sleep–wake_disorder