The glut of information that fills Justin Bieber's adorable noggin each day -- music, fashion, concert dates and, yep, screaming girls -- is keeping the 16-year-old pop star up at night. In the February issue of Vanity Fair, Bieber admits that he sometimes suffers from insomnia, an affliction he says is caused by a hectic life that doesn't afford time to think about "things that should be more important."