I was having a discussion about this with my Mrs last night. It's becoming the norm for people to let their kids stay up to 2-3 am playing online games on their devices. So these kids are getting dumbed down on multiple fronts. They miss out on social skills, they don't get the dark hours that a growing mind needs to sleep and develop properly, they get brainwashed by the games and the grammatically slaughtered shorthand chat and they are being trained to thrive off dopamine rushes.

I can't say for sure but sleeping after playing video games isn't a restful sleep (or it never was for me years ago when I played them), rather than having the daily recall where your subconscious mind makes sense of the day and reorganises its store of knowledge you tend to go sleep and your mind is still playing the game.