Insomnia

NOUN: A condition characterized by lack of the ability to sleep for prolonged periods of time, or otherwise extremely restless sleep. Often, insomniacs have trouble either falling asleep, staying asleep, or having a prolonged sleep cycle. If you're extremely unlucky, a combination of two or even all three of these characteristics can be present. Many (but not all) insomniacs tend to have underlying mental or emotional disorders that cause (or at least contribute to) the lack of sleep associated with insomnia. Also, a pretty damn decent Stephen King novel, if you're into long reads.