<unk>  <unk> , more often known as<unk>  sleep phase syndrome and also as<unk>  sleep–wake phase disorder, is a delaying of a person's circadian rhythm (biological clock), compared to those of the general population and societal norms. The disorder affects the timing of sleep, peak period of alertness, the core body temperature, rhythm, hormonal as well as other daily cycles. People with<unk>  generally fall asleep some hours after midnight and have difficulty waking up in the morning. People with<unk>  probably have a circadian period significantly longer than 24 hours. Depending on the severity, the symptoms can be managed to a greater or lesser degree, but no cure is known, and research suggests a genetic origin for the disorder. Affected people often report that while they do not get to sleep until the early morning, they do fall asleep around the same time every day. Unless they have another sleep disorder such as sleep apnea in addition to<unk> , patients can sleep well and have a normal need for sleep. However, they find it very difficult to wake up in time for a typical school or work day. If they are allowed to follow their own schedules, e.g. sleeping from 4:00 am to 1:00 pm, their sleep is improved and they may not experience excessive daytime sleepiness. Attempting to force oneself onto daytime society's schedule with<unk>  has been compared to constantly living with jet lag;<unk>  has been called "social jet lag". Researchers in 2017 linked<unk>  to at least one genetic mutation. The syndrome usually develops in early childhood or adolescence. An adolescent version may disappear in late adolescence or early adulthood; otherwise,<unk>  is a lifelong condition. The best estimate of prevalence among adults is 0.13–0.17% (1 in 600). Prevalence among adolescents is as much as 7–16%.<unk>  was first formally described in 1981 by Elliot D. Weitzman and others at Montefiore Medical Center. It is responsible for 7–13% of patient complaints of chronic insomnia. However, since many doctors are unfamiliar with the condition, it often goes untreated or is treated inappropriately;<unk>  is often misdiagnosed as primary insomnia or as a psychiatric condition.<unk>  can be treated or helped in some cases by careful daily sleep practices, morning light therapy, evening dark therapy, earlier exercise and meal times, and medications such as aripiprazole, melatonin, and modafinil; melatonin is a natural neurohormone partly responsible for the human body clock. At its most severe and inflexible,<unk>  is a disability. A chief difficulty of treating<unk>  is in maintaining an earlier schedule after it has been established, as the patient's body has a strong tendency to reset the sleeping schedule to its intrinsic late times. People with<unk>  may improve their quality of life by choosing careers that allow late sleeping times, rather than forcing themselves to follow a conventional 9-to-5 work schedule.
Delayed sleep phase disorder
Insomnia
Circadian rhythm sleep disorder
Non-24-hour sleep–wake disorder
Advanced sleep phase disorder
Shift work sleep disorder
Nightmare disorder
Rapid eye movement sleep behavior disorder