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Sleep And Exams: How Much Sleep Does A Teenager Need?


Teenagers are famed for their sleeping habits, whether it's sleeping in until midday or being awake until the early hours of the morning. How much sleep does a teenager need, and why is the relationship between teens and sleep often such a big issue, especially during exam periods?

10 a.m., Saturday morning

A brave dad somewhere risks walking into the bedroom of his sleeping teenager.

You know how important SATs are to your college applications. You HAVE to do well on them. You better buckle down; they’re coming up soon.

As college application deadlines loom for hopeful teenagers, it’s not just the temperature that starts to rise. Final exams and SATs are just around the corner, and teens and their parents are starting to feel the heat. And the pressure is increasing. In the US, the education system is forcing young people to make critical life choices and perform at their best at an increasingly young age. SAT scores and GPA are the only objective yardstick by which universities can judge candidates, and adequate grades in college will dictate nearly every future job offer for those that don’t go on to higher education.

So as the sun shines and an amazingly powerful—but 'still under construction'—teenage brain struggles to explore and test its environment, we try to lock it up in dimly lit rooms with a mountain of textbooks and wonder why things might go wrong. Stunning research by scientists like Sarah Blakemore Brown and many others has helped us to understand that different parts of the brain develop at different ages and that the last parts of the brain cortex to connect are the frontal and prefrontal areas, where insight, empathy, and risk-taking are controlled.

Remember this little neuroscience nugget when you next ask yourself why your very smart adolescent can still do very stupid things in an impulsive way.


12:30 a.m., Saturday night

A brave mom somewhere risks walking into the bedroom of her sleeping teenager.

What are you doing up? Do you know how late it is?! This is the most important year of your life. Don’t you know how important sleep is for your body and brain? Go to sleep now!

In fact, this frustrated mom is spot on. The problem with her approach is really the timing of her argument and its low chances of success. Melatonin is the hormone of darkness, which we produce in the evening when light levels are low. It helps to allow us to fall asleep. But a heated argument at 12:30 a.m. will increase levels of different stress hormones, including cortisol and adrenaline, which will make falling asleep much harder. And so neither will likely fall asleep quickly or peacefully on this night.

Mary Carskadon, an eminent adolescent sleep researcher, talks about the ‘perfect storm’ of factors that lead to lack of sleep for teens.

These include a natural change in body rhythms towards a later bedtime in the teenage years. For some young people, it’s a gradual progression towards bedtime one hour or so later. For others, it’s an inability to fall asleep until the early hours of the morning. Because morning start times don’t alter in most schools, the net effect is less time asleep.

There is increasing evidence about the role of sleep in helping memory and learning, mood and behavior, and physical health, and good guidance about normal ranges. But we need to avoid focusing on being ‘average,’ as we know that there are huge individual differences and some of us just need more sleep than others.


1:20 a.m., Saturday night

A brave dad somewhere risks walking into the bedroom of his teenager, lit by a dim blue glow.

Get off that phone now. I’m taking it. And I’m changing the wi-fi password!

Dad has a good point. Smartphones, even when turned off, emit blue light that can inhibit sleep. Manufacturers, realizing this, are finally offering “night modes,” with lower levels of blue light and more orange or red light that disrupt sleep patterns less.

But talking about color shades is often a moot point when your kid’s phone is dinging with notifications all night long. In a recent large study, parents estimated that more than two-thirds of older teens (15–17 years old) leave their phone on while sleeping at night, with 43% waking back up to read or send text messages after initially falling asleep. The parents of children who sometimes sleep with phones switched on at night estimate that their children sleep almost 1 hour less than children who never do so. We know that those children and young people who have well-established rules of limited caffeine and regular bedtimes and where neither parents nor children have devices in their bedroom sleep much better than those that don’t.


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Three Additions to Every Exam Timetable

  1. Light is a powerful ‘sleep and mood’ drug. Make sure your child gets at least 30 minutes of daily exposure to outside light, as close to waking up as possible. If the weather is really bad, then the ‘SAD’ blue lights can be used instead, but they are probably not required during the summer months.
  2. Make sure your child exercises every day. Even 20 minutes of vigorous exercise can improve your child’s slow-wave sleep, which will allow better retention of the facts they learned during the day.
  3. Focus on the positives of sleep. Sell sleep as a unique ‘hack’ that can improve learning, memory, and exam results. Plan study time and bedtime accordingly, working backwards from wake-up times to calculate bedtimes. And remember, sleep does not begin when your head hits the pillow, so allow 30 minutes for this. There are only rough guides for ‘how much sleep’ for each age group.

Three Tips About Electronic Devices

  1. Begin with a positive daytime conversation. Don’t underestimate the amount that young people can learn through news feeds, learning services, and other smartphone-based apps and tools. Many of these new study resources are built on sound learning principles but packaged into a portable device in a way not previously conceivable.
  2. Set an example. If you respect your highly intelligent teenager, who is able to process information faster than you, then don’t sit in your own bed with your phone or iPad on at night.
  3. Leaving smartphones out of the bedroom is ideal, but if that’s not feasible, then push for airplane mode before bedtime. Even one notification after bedtime is too many.

Three Thoughts on Reducing Battles

  1. Try to be supportive, acknowledge pressure, and avoid making plans and rules late at night.
  2. For anxious teens who can’t switch off, consider mindfulness and other relaxation strategies. Seek professional help if you are concerned about serious mood problems.
  3. Remember that even a small amount of extra sleep (40 minutes a night) will add up and make a difference in mood and performance. Keep your goals realistic and gradual. ‘Let’s begin by aiming to give you the time for an extra 40 minutes of sleep a night for the next month and see how you feel.