GHB has been called “almost an ideal sleep inducing substance” [SMART DRUGS II, p245]. Small doses produce relaxation, tranquility and drowsiness which make it extremely easy to fall asleep naturally. Higher doses increase the drowsiness effect and decrease the time it takes to fall asleep. A sufficiently large dose of GHB will induce sudden sleep within five to ten minutes [Laborit, 1964].
Many other hypnotics interfere with various stages of the sleep cycle thus preventing the body from achieving a complete and balanced session of rest and recuperation. The most remarkable facet of GHB-induced sleep is its physiological resemblance to normal sleep. For instance, GHB sleep is characterized by increased levels of carbon dioxide in the arteries, as in normal sleep [Vickers, 1969]. During normal and GHB sleep, the CNS continues to be responsive to “noxious stimuli” (pain and other irritations), a factor which sets limits on GHB’s uses in anesthesia [Vickers, 1969]. GHB facilitates both REM (rapid eye movement) sleep, and “slow-wave” (non-REM) sleep, the stage of sleep featuring increased release of growth hormone [Laborit, 1972]. And unlike the unconsciousness induced by other anesthetics, that triggered by GHB does not feature a systemic decrease in oxygen consumption [Laborit, 1964].
The primary disadvantage to GHB’s use as a sleep aid is it’s short-term influence–about three hours. During GHB’s influence, sleep is deeper and more restful, but after the GHB has worn off, people have a tendency to wake up. The higher the dose, the greater is this tendency. Some have called this pattern the “dawn effect” and have speculated that it is related to the release of stored-up dopamine. Some people minimize this effect by taking minimal doses of GHB. Others take advantage of this effect by getting a couple of hours of work done in the middle of the night. Still others choose to take a second dose of GHB to sleep for another three hours. It should be noted that not everyone can be put to sleep by GHB. We have spoken to three men who have never achieved sleep even with the doses normally used for such purposes. In addition, Takahara  reported that one of the six men in the growth hormone study cited above remained conscious even though he had received two and a half grams of GHB intravenously, a dosage which rendered the rest of the participants unconscious.