What is Delayed Sleep Phase Disorder (DSPD)?
Delayed sleep phase disorder (DSPD) belongs to a group of sleep disorders known as circadian rhythm sleep disorders whereby individuals experience a chronic pattern of sleep disturbance due to changes or misalignment in the circadian timing of their sleep, relative to what their social and physical environment dictate. It is this conflict that leads the expression of a problem. For example, an individual whose circadian rhythm, or 'body clock', is delayed may find that their ideal time for sleep is 4am with a rise time of 12 noon. This schedule does not match the typical sleep window of most adults; and thus the main problems of those with DSPS relate to attempting to fall asleep (before their body clock is ready to) and attempting to wake up in the morning (before their body clock is ready to). The latter can be an important problem if the individual has to commence work at 8 or 9am, rendering them with partial sleep deprivation
Circadian rhythm sleep disorders in general, lead to excessive daytime sleepiness as well as periods of insomnia, due to the shift in the natural, circadian timing of an individual's sleep window. DSPD in particular, tends to describe sleep-wake schedules which are delayed by two or more hours from the 'normal' so, for example, if an individual found themselves becoming sleepy at 4am and waking naturally at 12 noon. Other than this offset, DSPD does not cause 'abnormal sleep' and tends to follow a reliable pattern over a 7 day period.
Symptoms of DSPD
To meet the diagnostic criteria for DSPD according to the official DSM-IV manual of psychiatric disorders, the sleep disturbance must cause 'clinically significant' distress or impairment in an individual's social or occupational functioning or in any other important areas of their life. As in the diagnosis of other sleep disorders, this disturbance must not occur as a result of another sleep or mental health disorder or due to the physiological effects of any substances.
People with DSPD are commonly referred to as night owls , however, those with DSPD do not choose their waking hours, generally falling asleep very late at night and waking in the late morning or afternoon. DSPD will often lead to individuals being labeled as having insomnia but, importantly, they have no difficulty falling asleep if allowed to follow their internally set sleep pattern.
Treatment for DSPD includes a variety of lifestyle changes such as improvement in sleep hygiene habits, for example restricting caffeine intake in the hours before bed, keeping to a regular schedule and only using your bedroom for sleeping. Alternatively, 'bright light therapy' may help to reset the body clock, using controlled exposure to strong light levels shortly after awakening, or prescribed melatonin.