It has been one of our greatest mysteries since the dawn of time. Sleep has been greeted with contentment and relief, but also with apprehensionAnxiety that something bad will happen., for all of recorded history.

In Greek mythology, the gods of sleep (Hypnos) and death (Thanatos) are twin brothers. Scientists even found, unnervingly, that Stage 4 sleep resembles brain death or comaA state of unconsciousness in which a person is unable to respond and cannot be woken up..

But really, sleep is nothing to be afraid of. In fact, it is responsible for all of the workings of our minds and bodies. Missing sleep, on the other hand, can come with serious repercussions.

The list is endless. Short sleep can lead to high blood pressure, a heart attack or a stroke. It can cause hormonal changes in your body, reduce your fertility and decrease your resistance to colds and viruses. FatigueTiredness. leads to higher rates of depression and anxiety.

But chronic sleeplessness is a pandemic. We are advised to sleep for between eight to ten hours per day. Yet one quarter of adults in the UK routinely sleep for fewer than five hours, whilst one third report having insomniaA common sleep disorder which makes it harder to fall asleep, stay asleep or get good quality sleep..

Recently, the spotlight has turned to teens' sleeplessness. Studies from this year say that 70% of teens do not get the recommended nine hours of sleep per night required for their developing brains.

You might already be able to hear the voices of your teachers, parents or guardians. "Too much time on your phone! Too much blue light! Too much caffeine!"

Well, unfortunately, they are right... but only to an extent. In fact, it might please you to discover that scientists are now beginning to blame schools for the boom in teen insomnia.

Teenagers are made to function on an adult clock. Early in the morning, they head to school just as adults are heading to work. When adults want to go to sleep, children are expected to hit the hay too.

But some say this simply is not working. In teenagers, melatonin, a hormoneChemicals carried in the bloodstream that alter the way your body's systems act.  that plays a role in sleep, releases up to three hours later than in adults. But in the morning, melatonin is slower to leave the body in teens than in adults, leading to lethargy and drowsiness. An early school start may not be the best thing for the young body.

But phones are not in the clear yet. Artificial light also delays the release of melatonin too, and 89% of teens keep at least one device in their bedroom at night. The negative effect of blue light on sleep is well-established.¹

Yes: Adults mock teens for their mood swings, periods of intense tiredness and hormonal shifts. But this may provide an explanation for the difficulties of being young: the world is forcing teenagers to push against their biological clock, missing out on healthy sleep in the process.

No: This is one selective factor in the brains of teenagers which implies that their timetables are solely responsible for making them sleepier. In reality, if school started later, teenagers would also stay up later on their phones and would not sleep more than they do now.

Or... There are plenty more mysteries of the teenage brain to be unlocked, like why teens are more impulsive, changeable or imaginative. There is much to discover yet.