Thread by @DrMikeFarquhar

Adolescents often get a hard time about how - and when - they sleep.

Some basic misunderstandings about adolescent sleep physiology often lie at the heart of it.

Here’s what you need to know:

First of all, adolescence may not be what you think it is.

Adolescence is the period where body, brain and mind are transitioning from child to adult.

Physical changes in the brain continue into the early 20s, with frontal “executive” functions the last to fully mature

We all have an internal body clock, our circadian rhythm, that keeps us awake in the day and asleep at night.

When your body clock is out of sync - like when you’re jet lagged - it can be difficult to sleep at the right time

Most of us know if we’re more of a morning person or more of an evening person.

This is a natural, genetic, variation in our body clocks, and is as much a fact about us as our eye colour.

In adolescence however one of the changes that occurs is a natural shift in the timing of the body clock, usually by an hour or two.

We see this in the timing of release of melatonin, “the sleep hormone”, with adolescents’ levels rising, and peaking, later than adults

This physiological change in the body clock means adolescents often won’t feel at all sleepy at 10pm (often when parents want them to be going to bed) ... and won’t be ready to wake up at 7am when they are usually being shouted at to get out of bed

Keep that in mind, we’ll come back to it.

A question: how tall should a normal teenager be?

It’s (hopefully!) immediately obvious that that’s a question to which there is no single “right” answer.

Height is a continuous variable and at ANY age, there is a wide range of normal height (14 year old boy shown here for illustration)

Yet, when it comes to sleep, many people think there’s a right answer to “how much sleep do I (or my teenager) need?”

There isn’t.

Just like height, there is a range of normal sleep duration that changes with age (younger children shown here)

It means we have to think not about single figure answers for sleep duration, but ranges of normal, with most clustering around the median in a standard distribution curve.

One guide for sleep requirement across the lifespan is shown here

Teenagers are often quoted a figure of 9-9.5 hours as how much sleep they need. The problem is that that’s the median, and doesn’t tell you how much sleep any single teen needs.

Range of normal is 7-11 hours ... if you need 11 hours of sleep to recharge, that’s a real challenge!

Put those two things together:

- teenager’s brains are wired so they will often not feel sleepy until 11pm-midnight (for some it will be even later!)

- median sleep need is ~9.5 hours ... but may be longer

... and it translates to this ...

Asking a teenager to wake up at 7am is like asking an adult to wake up at 5am.

Every day.

Is it any wonder they’re tired and grumpy first thing?

It also means they’re also likely missing out on their last sleep cycle of the night, made up mainly of light sleep and REM, both of which play important roles in learning, memory and emotional regulation amongst other things

Pretty important stuff if you want to be at your best

Teenagers aren’t alone in being sleep deprived though, though they’re probably a bit more so on average.

Adults are as well ... and it’s usually because they’re not good at prioritising sleep in their lives

We’re all good at coming up with things that we think are more important than sleeping, a finding that’s found in similar cultures across the world

Let’s think about TV for a moment.

@netflix’s CEO was asked last year who his biggest competitor was.

To the interviewer’s surprise, he said “sleep”

Here’s how he thinks about sleep.

It’s the only time he knows you’ve got for him to prey on so he can make money.

He’s turning your sleep deprivation into profit.

Why does it matter if you’re watching @Netflix before bed?

It’s all to do with light. Light is the main cue that helps keep your body clock in sync with the world.

When you travel, your body clock resets over a few days with the new pattern of light/dark exposure.

When we evolved, the only real bright source was the sun. Moon and fire were much dimmer light sources at night ... so our body clock evolved to match light with wake, dark with sleep.

The invention of electric light transformed our world - we can have bright light whenever we want it.

Lots of advantages to that - but not good for our body clocks.

We should think about light at night like this: it’s a drug which makes us want to be more awake and more alert.

Light when the brain isn’t expecting it will affect sleep, both quality and getting to sleep

That means this is a problem: if the last thing we see at night is a bright light source like a phone, or laptop, it confuses our brains ... it makes us think it’s earlier in the day than it is, and rewires our body clocks to a different time zone

It suppresses the natural production of melatonin, the hormonal signal triggered by your body clock to tell the rest of your brain and body it’s time for sleep

(Night shift modes don’t help I’m afraid: evidence so far tells us that phones with these switched on still have significantly negative affects on sleep duration and quality)

There’s also a psychological effect of being on devices: how often have you found yourself falling down the YouTube or Wikipedia black hole at bedtime?

Add all those things up, and it means teenagers often feel like this when listening to well-intentioned but just *wrong* advice they are given about their sleep

(That’s also why Netflix love the binge watching model ... exploits you psychologically to make them money. The bad news is adults who binge-watch TV are more likely to have poorer quality sleep, and less of it: jcsm.aasm.org/viewabstract.a… )

For teenagers who also have a chronic health condition, sleep deprivation can contribute to worse symptom control.

It’s often worth thinking about sleep if you’re struggling with optimal symptom control.

As with anyone who is sleep deprived, there are consequences, and teenagers are just as vulnerable (possibly more so)

Helping improve their sleep is likely to help improve both their physical and mental health

The @nhs choices website has some sleep advice for teenagers (and their families)

nhs.uk/live-well/slee…

Teachers, parents, doctors and teenagers themselves all need to be supported to better understand how their brains handle sleep

A more teenage-orientated approach to sleep can have significant benefits for everyone!

(And that’s your basic adolescent sleep tutorial)