From the way he behaves I really doubt he has insomnia, and I doubt the depression as well. Growing up his grandparents always had him on this golden pedestal like he was some child God or something andmake it clear that he should have to do nothing to get through life as everything should be handed to him while everyone else that behaves in such a manner is nothing but scum. Even now they act that way so I'm thinking he is just trying to get by on that entitlement but because he is their boy, my parents do not want to see this. They do not want to see the fact that he does not sleep at night is because he is out getting high and drunk, and will believe every word he says even though my sister and I have proved he is a chronic liar. But anyways, thank you ticked, you said exactly what I had felt about this for a while now.
I think he might be having insomnia type of sleep disorders, its very difficult to cure when becomes chronic and may be he is undergoing the same thing. Give him some time.
I think that it is possible that he could have some sort of sleep issue but if you are sleeping all day long and up all day night its not insomnia. He has made his mental clock to act as if he is working a night shift.
It is possible that he suffers from depression, doing drugs doesnt help.
If that is not the case he could just be very irresponsible, lazy and not ready to get out into the real world.