Can you include links to some of this research? That is fascinating. I have a friend who is an extreme night owl who has long said then when he sleeps matters

Can you include links to some of this research? That is fascinating. I have a friend who is an extreme night owl who has long said then when he sleeps matters far more than how much—but in a negative sense. Even if he gets as much as 10 hours of sleep, if he has to go to sleep early in order to wake up early (6-7am), he’ll be miserable. If he goes to sleep at 3am and wakes up at 9:30am, he’ll feel great despite having gotten much less sleep.