What is it?
Delayed sleep-phase syndrome (DSPS) is a chronic dysregulation of a person’s sleep-wake cycle. The most visible symptoms often present themselves as falling asleep a lot later than the general norms of the surrounding society would allow, even if the person is regularly woken up after insufficient sleep. The syndrome also affects the person’s peak times of alertness, as well as the rhythms of body temperature and hormones.
Those with DSPS often fall asleep at approximately the same time every night and have a normal need of sleep. An example of this could be having to wake up for work every day at 7AM, but never falling asleep before 3AM. Forcing oneself to the socially approved rhythm can cause jet lag -like symptoms, and DSPS is, indeed, sometimes referred to as “social jet lag”.
DSPS affect around 0.15% of adults and as much as 7-16% of adolescents.
What causes it?
The cause of DSPS is not known, but those with a family history of the syndrome are 3 times more likely to have it themselves, suggesting a genetic link. About half of the reported DSPS patients have suffered from depression or other psychiatric problems. While this obviously doesn’t prove any causal relationship between the two, they are definitely linked. Depression is associated with altered serotonin levels, though, and since the sleep hormone melatonin is serotonin’s precursor, it is quite conceivable why depression could lead to sleeping difficulties.
What happens during it?
DSPS occurs, because the body’s own biological clock isn’t in sync with the environment. Our bodies have an intrinsic rhythm, but it can be affected by environmental factors such as sunrise, sunset, and our daily routines. Several mechanism have suggested to underlie DSPS, but the truth probably lies somewhere between having an abnormally long “biological cycle” and failing to respond normally to environmental triggers.
When it’s dark and/or time to sleep, our brains start to excrete melatonin, which makes us sleepy. Being exposed to light makes us produce less of the hormone. It has been found that people with DSPS are more sensitive to light stimuli: their melatonin production is reduced much more easily than in healthy people.
If normal people sleep poorly one night, they generally fall asleep early the next. When this happens, the body detects that they have had more exposure to light before bed than normal, and their circadian clock adjusts to this. In people with DSPS this “resetting” doesn’t occur, and it is difficult for them to fall asleep before their normal sleeping time. As mentioned briefly earlier, this can lead to considerable difficulties if one’s normal falling asleep-time is, for example, at 3AM, and they routinely have to wake up at 7AM.
How can it be treated?
While DSPS can’t be cured, the symptoms can be managed, although with varying degrees of success. It can be helpful to maximize exposure to light in the morning and to minimize it in the evening. Melatonin can also be taken to produce sleepiness.
Sources: https://en.wikipedia.org/wiki/Delayed_sleep_phase_disorder, https://www.sleepassociation.org/patients-general-public/delayed-sleep-phase-syndrome/, https://en.wikipedia.org/wiki/Circadian_rhythm_sleep_disorder