Walker discusses four sleep disorders, which support his claim that “few other areas of medicine offer a more disturbing or astonishing array of disorders than those concerning sleep” (237). 

One example is somnambulism, which refers to sleep disorders that involve movement (e.g., sleepwalking, sleep texting, sleep sex, sleep talking, sleep eating, and in rare cases sleep homicide). These events occur during NREM sleep, with one trigger being a sudden burst of nervous system activity. Somnambulism occurs in both child and adult populations. Episodes are typically harmless, although Walker provides one rare example where an episode led horrifyingly to homicide.

Another example is insomnia—the most common sleep disorder, which affects more women than men—where individuals cannot generate sleep despite allowing themselves opportunities to do so. Triggers include environmental, medical, physical, psychological, and physiological factors. Because individuals with insomnia have lower sleep quality, their cognitive and emotional states do not function as well during the day. As such, “insomnia is really a 24/7 disorder: as much a disorder of the day as of the night” (246).

Walker saves the most horrifying of the chronic sleep disorders for last: fatal familial insomnia, a genetically inherited disorder characterized by insomnia.