Delayed sleep phase disorder

Delayed sleep phase disorder
Other names	Delayed sleep–wake phase disorder, delayed sleep phase syndrome, delayed sleep phase type, social jetlag
Comparison of standard (green) and DSPD (blue) circadian rhythms
Specialty	Psychiatry, sleep medicine

Delayed sleep phase disorder (DSPD), more often known as delayed sleep phase syndrome and also as delayed sleep–wake phase disorder, is the delaying of a person's circadian rhythm (biological clock) compared to those of societal norms. The disorder affects the timing of biological rhythms including sleep, peak period of alertness, core body temperature, and hormonal cycles.

The diagnosis of this disorder is currently a point of contention among specialists of sleep disorders. Many insomnia-related disorders can present significantly differently between patients, and circadian rhythm disorders and melatonin related disorders are not well understood by modern medical science. The orexin system was only identified in 1998,^[1] yet it appears intimately implicated in human sleep-wake systems.

Evidence for the plasticity of human circadian rhythm cycles has been provided by multiple studies. In one example, several dozen volunteers spent many months underground in a French cave, while researchers monitored their periods of waking and sleeping. Their results found significant divergence between individuals, with most participants settling upon a rhythm of 30 +/- 4 hours.^[2] Researchers have speculated that the lack of exposure to natural sunrise/sunset cycles relates many of the symptoms of these circadian disorders to modern habits of humans spending extended periods indoors, without sunlight exposure and with artificial light.

Symptom management may be possible with therapeutic drugs such as orexin antagonists or melatonin receptor agonists, as well as regular outdoor exercise. There may be a genetic component to the syndrome.^[3]