Insomnia or sleeplessness is a sleep disorder which causes difficulty in falling asleep, or staying asleep as long as desired. It also leads to excessive daytime sleepiness, low energy and a depressed mood. Treatment for insomnia usually involves sleep-inducing medication, cognitive behavioral therapy for insomnia (CBT-i), or a combination of both. Orexins are neurotransmitters in the body that regulate feelings of sleepiness and wakefulness. An orexin antagonist inhibits the effects of orexin, and can be used to treat insomnia. This book provides comprehensive insights into the field of insomnia treatments. It is compiled in such a manner, that it will provide in-depth knowledge about the therapeutic potential of orexin antagonist. This book will serve as a reference to a broad spectrum of readers.