hypnagogic« Back to Glossary IndexHypnagogic is the transition from wakefulness to falling asleep. Related Articles: Guide for Sleep & Research Study CentersConsiderations for ProfessionalsAbout Related Sleep Disorders (Hypersomnias)Glossary: hypnagogic hallucinationsGlossary: narcolepsyAsk the Doctor: Narcolepsy vs Idiopathic HypersomniaIt’s a Fine Line Between Type 2 Narcolepsy and Idiopathic Hypersomnia… and It’s Getting Even Finer