Teens and Sleep

Late nights, night time screen use and school starting times damage healthy sleep patterns By Denis Lundie

School starting times, later bedtimes and evening exposure to light impair the length and quality of teens’ sleep. Together, they can lead to an accumulating sleep deficit for teens, besides reducing alertness and concentration levels in the morning.

The school day, and the adult day, are out of sync with the adolescent biological clock

This is not news to parents, but they can take some comfort that parenting strategies will not change adolescent biology. Timing of the school day leaves teens sleep-deprived. The sleep-wake cycle, or circadian rhythm, of children shifts later in the day as they enter their teens. This biological ‘phase shift, common to many mammals entering puberty, makes it hard for them to go to sleep early or to get up early.

What parents can do, is adjust the sleep-wake expectations they have of teenagers. Expecting an adolescent to get up at 7 a.m.  and start school at 9 a.m. is similar to asking a 55-year old to get up at 5 a.m. according to the Teensleep research team in the Oxford University Medical Sciences Division. Insisting on an early bedtime to fit in the recommended minimum of 8-9 hours before 7 a.m., has little value, and can add complications because teens will find it very difficult or impossible to go to sleep at 11 or 10p.m. Quality sleep for healthy cognitive and emotional functioning has as much to do with when teens sleep, as how much they sleep.

Schools and education authorities can take account of neuroscience research and reconsider school starting times. Some UK schools, like UCL Academy, and school boards in Canada, have already moved their school day later by an hour or more. Research is in progress with a number of UK schools to assess the learning impact that a later start to the school day will have.

Later bedtimes, online socialising and light-emitting devices make matters worse

Teens’ sleep situation also made worse by more relaxed social attitudes to bedtimes, online social interaction with exposure to light from electronic equipment in the evening. These extend their ‘wake’ cycle further into the night, and affect the length and quality of sleep even more. Light, particularly in the ‘blue’ spectrum emitted by television, computers and mobile phones, suppresses the body’s production of melatonin, the hormone which stimulates the ‘sleep’ cycle. Night-time exposure affects this rhythm well into the following day, and permanently if late night light exposure is routine. Professor Carskadon, a leading researcher in the area, refers to this ‘Perfect Storm of Adolescent Sleep’ where biological, psychological and social factors combine to erode teen sleep in the morning and in the evening, with negative impact on cognitive performance and motivation.

What can be done?

Professor Carskadon suggests to pediatricians to promote the following, which could also help parents:

  1. Encourage schools to consider starting the school day later for adolescents and recommend that schools also limit late-evening activities;
  2. Galvanise schools to provide instructional information about sleep and circadian rhythms;
  3. Support and encourage parents to identify and set an appropriate bedtime;
  4. Encourage teens to avoid light and stimulating activities in the evening and to get light exposure in the morning;
  5. Empower adolescents to make informed choices about their sleep schedules;
  6. Remind families of the utility of a relaxing pre-sleep ritual.


  1. Read Sleep in Adolescents: The Perfect Storm, by Mary A. Carskadon in thePediatric Clinics of North America, Volume 58, Issue 3, Pages 637-647
  2. Find out about Teensleep Research at the Nuffield Department of Clinical Neurosciences, Medical Division at Oxford University.
  3. Read about ‘blue’ light and light emitting devices in the Scientific American.
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