We're all used to seeing strange things in our dreams, but what about when we're not dreaming? So-called hypnagogic hallucinations occur during the transition from wakefulness to sleep (just after our head hits the pillow). And hypnopompic hallucinations hit during the waking-up process. People report hearing voices, feeling phantom sensations and seeing people or strange objects in their rooms. Bugs or animals crawling on the walls are a common vision, said Neil Kline, a sleep physician and representative of the ASA.
Sleep-related hallucinations are most common in people with narcolepsy. So while the occasional phantasmic visitation is nothing to worry about, if the hallucinations are accompanied by daytime sleepiness and loss of muscle control when excited or surprised, Kline recommends you see a doctor.