Inability to stay awake until a reasonable bedtime. Individuals with ASPS find that they begin to get uncontrollably sleepy at a very early hour, often well before 9:00 PM.
Inability to wake up at a reasonable hour. Even if the individual with ASPS is able to hold off sleep until later in the night, they often find it impossible to stay asleep past an unusually early hour of the morning (sometimes as early as midnight or 1:00 AM).
Tendency toward falling asleep earlier each night. This symptom generally appears in conjunction with waking up a proportional amount earlier the next day.
The above symptoms continue for at least three months in cases of Advanced Sleep Phase Syndrome.
Symptoms of Delayed Sleep Phase Syndrome
Reversal of circadian rhythms. Individuals with DSPS feel the need to sleep during the day and stay awake at night.
Feeling more alert at night. People with DSPS often describe themselves as "night owls."
Excessive daytime sleepiness. DSPS sufferers often find they require naps during the day in order to function.
Difficulty falling asleep quickly. With DSPS, it takes a long time – as much as 20-40 minutes – to fall sleep.
