Concussion is getting more attention than ever before, with debates about when sportspeople should and shouldn’t be let back onto the pitch after a bang on the head.  Many are still campaigning for the consequences of traumatic brain injuries, in the short and the long-term, to be taken more seriously.

But one common misconception is that a person who’s had a bang on the head shouldn’t be allowed to go to sleep in case they slip into a coma.  However, this is not the current medical advice that’s given because evidence doesn’t back it up.  

Concussion is an injury caused by a heavy bang on the head or a sudden, strong jolt to the brain, in a car crash, for example.  People are right to take blows to the head very seriously.  There can be serious consequences and part of the difficulty is diagnosing the severity of an injury.  

In the US alone there are an estimated 1.6 to three million traumatic brain injuries each year. At the moment doctors have to rely on looking for symptoms such as vomiting, confusion, a loss of balance, blurred vision or headaches, tingling in the arms or the legs to establish how serious an injury might be.

There are high hopes for a simple blood test which might be able to detect concussion in the future by measuring certain substances in the bloodstream. It’s just been discovered by a team at Orlando Regional Medical Centre in Florida that these two proteins are released by the brain when a blow to the head has damaged it.

The reason the fear of letting people sleep has come about, is due to what’s known as the lucid interval

A test will take a few more years to develop and in the meantime doctors have to rely on the observation of symptoms.

The fear of letting people sleep has come about from a misunderstanding of the “lucid interval”. This is rare, but it’s the name for the period of time after someone wakes up from being unconscious, and seems fine, but meanwhile their brain is bleeding, a state known as a haematoma, is causing pressure on the tissue of the brain. If this causes them to lose consciousness again, this time it’s a medical emergency.

But even when someone does have a bleed on the brain, this lucid interval only occurs in a minority of cases.

However, the possibility of a bleed on the brain is the reason that it is important to look out the symptoms I mentioned before if you are with someone who has banged their head. These guidelines are given by many different organisations from World Rugby to Britain’s NHS. But if someone is not confused or vomiting, or has double vision or trouble walking or a severe head or neck ache, these recommendations do not include the advice to keep them awake. In fact rest is what’s needed, both physically and cognitively.  

So athletes have to stop training for a time, but should also stop taxing their brains. Children should do less school work, for example, until they have fully recovered.  The brain needs to heal by not doing so much and so sleep is perfect for it.  It’s not bad, it’s a good thing.

This is the current advice. Although it should be said, that until very recently, very few trials have tested the advice that is given, something that worries some researchers.

Some organisations do recommend that if a child has sustained a head injury, they should be woken every hour or two on the first night

The good news is that several news trials have been registered and are underway, so we should soon have more information on the best way to treat concussion and to care for people after a head injury.

Part of the confusion here, surrounds the term concussion. It sounds so benign that some doctors argue that we should always aim to call it traumatic brain injury instead.

But some organisations do recommend that if a child has sustained a head injury, they should be woken every hour or two on the first night to check that they are still alright and that they can hold a conversation, before allowing them to go back to sleep again.

So sleep is recommended, but that doesn’t always mean it’s easy.  Research reveals a variety of different sleep disorders which are more common after concussion, in particularly insomnia, fatigue, and sleepiness and sometimes even narcolepsy or sleep apnea.  

Join 600,000+ Future fans by liking us on Facebook, or follow us on Twitter, Google+, LinkedIn and Instagram.

If you liked this story, sign up for the weekly features newsletter, called “If You Only Read 6 Things This Week”. A handpicked selection of stories from BBC Future, Earth, Culture, Capital, Travel and Autos, delivered to your inbox every Friday.

All content within this column is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. The BBC is not responsible or liable for any diagnosis made by a user based on the content of this site. The BBC is not liable for the contents of any external internet sites listed, nor does it endorse any commercial product or service mentioned or advised on any of the sites. Always consult your own GP if you're in any way concerned about your health.