Tired, grumpy, moody… This might sound familiar if you’re the parent of a teenager, but we should cut them some slack and try to understand why they can’t seem to get out of bed in the mornings. In a three-part series of articles, Harvard’s Dr. Judith Owens, who has spent decades researching the science behind sleep, shares her expertise and helpful tips to help your kids get a good night’s sleep.

The Importance of Sleep

Sleep is essential to health, safety, productivity and well-being. A sufficient amount to meet sleep needs and appropriately-timed sleep is as important as nutrition and exercize. The only thing that replaces sleep is: SLEEP.

Sleep in School-aged Students

According to Dr. Owens, primary school-aged children should be sleeping between 10-12 hours a night. They tend not to feel sleepy during the day but their circadian preference, or chronotype, may differ depending on whether they are an “owl” or a “lark”.

Sleep in Adolescents: Later Bed Times

All adolescents experience a normal shift in circadian rhythms with age and in association with the onset of puberty. This results in a biologically-based shift (delay) of up to several hours in both the natural fall sleep and morning wake times. This means that it’s almost impossible for the average adolescent to fall asleep much before 11pm on a regular basis. Teens cannot “make” themselves fall asleep earlier.
Dr. Owens points to two main environmental factors affecting their sleep schedules. Firstly, their competing priorities for sleep. Homework, activities, after-school employment, “screen time” and social networking may all have a part to play in affecting their sleep. Secondly, their circadian phase delay may be further exacerbated by evening light exposure as light from screens suppresses release of melatonin in the brain.

Adolescents: Later Wake Times

These biological changes are in direct conflict with earlier high school start times (before 8:30am) because adolescents are biologically programmed to wake at 8am or later. As a result, students are required to wake for the day and function during the “circadian nadir” (the lowest level of alertness during the 24-hour day). Early wake times also selectively rob teens of REM (rapid eye movement) sleep, which is critical for learning (of new information, in particular) and memory.

Adolescents: “Make-Up” Sleep

Contrary to popular belief, later bed and especially wake times on weekend do not compensate for weekday sleep loss and associated performance impairments. In fact, it exacerbates the body’s normal shift in circadian rhythms and leads to “social jet lag.” This adjustment takes one day for each time zone crossed and effects can persist for up to 3 days, leading to daytime sleepiness, poor academic performance and a depressed mood.

Adolescent Sleep: The Bottom Line

Most adolescents do not get sufficient amounts of sleep, which is critical for their overall well-being. A study conducted in 2016 found that 94% of 481 Chinese adolescents in 12th grade preparing for the College Entrance Exam got less than 8 hours of sleep. For optimal health, safety and achievement, the average sleep high school student needs is 8.5 to 9.5 hours of sleep. In 2016, the American Academy of Sleep Medicine recommended 8 to 10 hours of sleep for children between the ages of 13 to 18, while children between 6 to 12 years of age should be sleeping 9 to 12 hours.