I believe I suffer from what Douglas Coupland calls Fictive Rest:
The common inability of many people to be able to sleep until they have read even the tiniest amount of fiction. Although the element of routine is important at sleep time, reading fiction in bed allows another person’s inner voice to hijack one’s own, thus relaxing and lubricating the brain for sleep cycles. One booby trap, though: Don’t finish your book before you fall asleep. Doing so miraculously keeps your brain whizzing for hours.