Genetic factors in sleep disorders.

Several sleep disorders have a genetic basis. These conditions include the narcoleptic syndrome, sleep walking, periodic movements in sleep, circadian delay syndromes and familial insomnia. These disorders illustrate different control mechanisms involved in sleep and wakefulness, including those determining the prevalence and timing of NREM and REM activity, somatomotor inhibition and excitation, autonomic discharge, and the circadian framework of sleep. The genetic defect in narcolepsy has been localised to the short arm of chromosome 6, but the chromosomal localisations of the genetic basis for the other disorders are not known. Also, with the possible exception of acetylcholine, no definite neurotransmitter involved in any aspect of sleep regulation has been positively identified and the biochemical defect in narcolepsy is not known.