DPSS is rare and affects mainly people in their teens and twenties. While many teenagers and young adults demonstrate night owl characteristics because of self-imposed lifestyle, some are unable to fall asleep during the usual bedtime hours and find it impossible to sleep until four or five in the morning.

If school or work dictates arising at a certain time each morning, the individual may be forced awake by a screeching alarm clock or a nagging parent after only three or four hours of sleep. For students, this usually results in their inability to stay awake in morning classes. In many cases, poor grades occur because of continually being sleep-deprived which may affect alertness, memory, and concentration. For workers, this can mean daytime sleepiness that results in lower productivity and performance. In either case, quality of life suffers.

For those who complain of their inability to fall asleep at the desired bedtime, inability to awaken at their desired wakeup time, and excessive sleepiness, they may suffer from a sleep disorder called Delayed Sleep Phase Syndrome, more simply referred to as Phase Delay Syndrome.

If you are unable to fall asleep within two hours of your ideal time over a two-week period, your condition is mild and you may experience mild impairment of social or occupation functioning. If the average is three hours and the condition has lasted one month, you are experiencing moderate severity and impairment. If the average is four hours, and the condition has gone on for over a month, severe impairment is present at this level.