A family of sleep disorders that affects the timing of sleep (among other things). Circadian rhythm sleep disorders may be characterized as either extrinsic or intrinsic.
Formerly known as sleep-wake schedule disorder; a dyssomnia consisting of sleep disruption leading to excessive sleepiness or insomnia that is due to a mismatch between the sleep-wake schedule required by a person’s environment and his or her circadian sleep- wake pattern. In the delayed sleep phase type, sleep onset and awakening times are late, and the person is unable to fall asleep and awaken at a desired earlier time. The jet lag and shift work types include sleep disruption produced by jet lag and by recurrent changes in work shifts, respectively; they are characterized by insomnia during the major sleep period or excessive sleepiness during the major awake period.