Delayed sleep phase disorder
Delayed sleep-phase disorder (DSPD), also known as delayed sleep-phase syndrome (DSPS) or delayed sleep-phase type (DSPT), and in the 2014 revision of the International Classification of Sleep Disorders (ISCD-3), delayed sleep-wake phase disorder, is a dysregulation of a person's circadian rhythm (biological clock), compared to the general population and relative to societal norms. The disorder affects the timing of sleep, peak period of alertness, the core body temperature rhythm, hormonal and other daily cycles. People with DSPD generally fall asleep some hours after midnight and have difficulty waking up in the morning. They probably have a circadian period significantly longer than 24 hours.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 DSPD, 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 3:00 a.m. to 12:00 noon, their sleep is improved and they may not experience excessive daytime sleepiness. Attempting to force oneself onto daytime society's schedule with DSPD has been compared to constantly living with jet lag; DSPD has, in fact, been referred to as ""social jet lag"".The syndrome usually develops in early childhood or adolescence. An adolescent version may disappear in late adolescence or early adulthood; otherwise DSPD is a lifelong condition. Depending on the severity, the symptoms can be managed to a greater or lesser degree, but there is no known cure. Prevalence among adults, equally distributed among women and men, is approximately 0.15%, or 3 in 2,000. Prevalence among adolescents is as much as 7–16%.DSPD is also genetically linked to ADHD by findings of polymorphism in genes in common between those apparently involved in ADHD and those involved in the circadian rhythm and a high proportion of DSPD among those with ADHD.DSPD was first formally described in 1981 by Elliot D. Weitzman and others at Montefiore Medical Center. It is responsible for 7–10% of patient complaints of chronic insomnia. However, since many doctors are unfamiliar with the condition, it often goes untreated or is treated inappropriately; DSPD is often misdiagnosed as primary insomnia or as a psychiatric condition. DSPD can be treated or helped in some cases by careful daily sleep practices, light therapy, dark therapy, and medications such as melatonin and modafinil (Provigil); the former is a natural neurohormone responsible partly and in tiny amounts for the human body clock. At its most severe and inflexible, DSPD is a disability. A chief difficulty of treating DSPD 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 DSPD 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.