Normally, our sleep-wake cycle approximates a 24-hour diurnal rhythm. We sleep during the dark part of the day and are awake during the light part. When studied in an artificial time-isolation environment, however, most humans demonstrate a free-running, endogenous rhythm of 25 hours. The 1-hour discrepancy each day requires that our biological clocks be reset by “zeitgebers,” or stimuli that entrain our natural rhythm to a shorter period. The process is called phase delay and is accomplished by exposure to exogenous light, dark, and social interactions occurring at particular points in the 24-hour day (Wagner 1990). That is, both our sleeping and waking lives are regulated by a variety of time cues designed to enhance good sleep hygiene and the regular resetting of our biological clock. Within limits, schedule irregularities, such as staying up later or arising earlier by 1-2 hours, can be tolerated for short periods without upsetting the phase of the clock.
However, prolonged periods of sleep deprivation or persistent irregularity in sleep hygiene inevitably leads to circadian rhythm disorders. Jet lag syndromes resulting from rapid time zone changes and the dyssomnias of shift workers resulting from continuously changing schedules are typical examples.
Adolescence is also a time of disrupted schedules. Pressures at school and new social obligations cause adolescents to stay up late. Many adolescents have additional work demands, either athletic or occupational, that entail an extra commitment of hours (Carskadon 1990). Therefore, adolescence is a period when persons begin to stay up later and later. During the week, however, school schedules continue to require that adolescents rise early. Soon they become significantly sleep deprived. The problem is compounded when they “sleep in” on weekends, further disrupting their biological clock. Approximately 30% of adolescents report falling asleep in school. Many more complain of tiredness. Because adolescence is also the period for learning to drive motor vehicles and for experimenting with drugs and alcohol, the public health and personal safety issues involved in excessive sleepiness in adolescence are significant (Carskadon 1990).
The typical delayed sleep phase syndrome of adolescence is characterized by an inability to fall asleep at a usual bedtime and an inability to get up at a reasonable hour in the morning. The sleep log reveals bedtimes that do not result in rapid sleep onsets, sleep-onset times that are intractably later than the social norm (usually after 2:00 a.m.), little difficulty in maintaining sleep once asleep, and difficulty awakening at an appropriate hour in the morning. The total number of hours of sleep per night is reduced sharply, although on weekends, total sleep time is lengthened, with awakenings in the late morning or early afternoon. Once the biological clock is disrupted, the delayed sleep phase syndrome frequently persists during vacations, even when normal amounts of sleep are obtained and sleep debt is no longer significant. Similarly, when bedtime is regularly enforced, such as in a summer camp, the adolescent with delayed sleep phase syndrome typically cannot fall asleep until after midnight.
Treatment of this disorder is difficult, requiring a highly motivated adolescent and a supportive family. A careful profile of all of the adolescent’s social and academic demands needs to be obtained. Assistance with stress reduction and daytime scheduling needs to be provided. Treatment may be easier to institute during vacation. A regular, more normal bedtime must be set and a daily sleep log kept. An MSLT may be necessary to assess the amount of sleep debt. Treatment should focus both on eliminating the sleep debt and on restoring a more normal sleep-onset time and waking time.
If supportive approaches directed toward stress reduction, better daytime scheduling, and improved nightly sleep hygiene are not successful, chronotherapy, or resetting of the biological clock, may be indicated. Most often, further phase delay is prescribed. A regimen of delaying both sleep times and rise times by 1-2 hours each day attempts to shift sleep onset to a more appropriate time. The treatment is stopped when bedtime and sleep-onset times approximate 10:00 to 11:00 p.m. Subsequently, this schedule needs to be maintained rigidly or the delayed sleep phase syndrome will progressively return.
Phase-advancing the clock also has been reported to be successful in some adolescents. This procedure requires that the adolescent go to bed 15-30 minutes earlier each night. The advance needs to be gradual, with small shifts instituted every few nights. Phase advance is a slower process than phase delay. Weekly improvements of 15-30 minutes may be all that is possible. Antipsychotic and hypnotic medications are not helpful in promoting sleep onset. The duration of delayed sleep phase syndrome symptoms varies from months to decades. Adolescents appear to be particularly vulnerable to the development of this syndrome.
Revision date: June 21, 2011
Last revised: by Tatiana Kuznetsova, D.M.D.