We underestimate the value and importance of sleep at our teenagers’ (and our own!) peril, and if there is one thing we can do to really help their mental health and well-being on multiple levels, it is to explain to young people the importance of sleep and encourage them to get their nine (yes nine!) hours a night.

Teenagers. Known for being up at night and asleep in the day, and irritable with it … How and why does this happen, and why does sleep, and getting enough of it, matter? Understanding this might help us as parents better understand what’s happening for them, why it matters that they get their ‘beauty’ sleep and how we can support them in a way that is pragmatic and tolerant.

Sleep is not neutral; it is a daily opportunity for the body and brain to process and repair after the day’s labours. During sleep our brains have been shown to light up with activity as these processes get to work. Missing this opportunity can have significant negative consequences on physical and mental health. Dr Leila Tomkins, a UK neurologist and sleep doctor, tells her teenage patients that, ‘You are “revising” all your new learning when you’re asleep.’ She told us, ‘When young people get fewer than eight to ten hours’ sleep a night, they risk negatively impacting on the three Ms: mood, memory and metabolism, for example food cravings go up and weight gain can follow.’

It won’t cheer you either to discover that ‘catching up’ on sleep in one of those wonderful vw campervan conversions is a myth – once it’s missed, it’s missed, and there is no way to regain that lost opportunity to repair and recuperate. Matthew Walker, a world-renowned sleep doctor, states that this is one of the primary messages we should take from his book Why We Sleep.

One of the most fascinating phenomena linked to adolescent sleep is the shift in their body clock (circadian rhythm) between childhood and adulthood. This is their daily sleep–wake cycle, that primary urge we have to be awake when it’s light and asleep when it’s dark. As children that urge to sleep comes on in the early evening, and as adults at around 10pm or 11pm in general. However, in puberty the brain shifts its onset of sleepiness dramatically to about 1am. For girls, the shift will likely happen between the ages of 11 and 13, and for boys a little later. With the teenage need for approximately nine hours’ sleep you can see how they then might want to sleep until late morning. While this can be accommodated by an understanding and supportive parent at weekends, our society is (unfortunately for teenagers) run by adults not adolescents, so we force them to get up at 7am or earlier, which would be the equivalent of 4am or 5am every weekday for us! They feel groggy, exhausted and irritable, with good reason. Such feelings are known as ‘social jetlag’, and can occur in anyone forced to be awake for work or social reasons, when they would normally be asleep.3 Anyone thinking that teens should just go to bed earlier, should bear in mind that you can’t force them to sleep sooner, as their brain literally can’t ‘switch off’ until the early hours of the morning. You are setting yourself up to fail if you try to force them to do this.

They are trapped in their teenage brains in an ‘adult-adjusted’ society, until eventually, in their mid-twenties, their rhythm (body clock) shifts back again, just in time for entry to the workplace for some.

In case you are wondering how evolution got this so wrong, it didn’t. It is thought that this generational difference is another possible example (along with finding their parents excruciatingly embarrassing) of how evolution encourages young people to separate from their family, creating a time during which all the teenagers of the ‘tribe’ would have been awake together without parents or children around, allowing them to develop their self-identity. It may also explain (partially) why teenagers are often so grumpy!