Teenage pop star Justin Bieber is often left tired and grumpy because he struggles to fall asleep at night.
The Baby hitmaker admits he finds it difficult to drift off and blames his hectic work schedule for keeping him awake.
He tells Vanity Fair magazine, "I just turn over all night and think. My mind races. I think about all the things I didn't have time to think about during the day - like family and God and things that should be more important but you don't have time to think about, because you just get caught up (in everything else) during the day."