Mild traumatic brain injury (mTBI)

Key points about concussion

  • A concussion is a mild traumatic brain injury (mTBI). It happens when a bump, blow or shake to your head or body transmits a force to your brain.
  • You may or may not lose consciousness.
  • A concussion affects how your brain functions. Symptoms are varied but include headache, nausea, light-headedness or dizziness, loss of balance, poor memory or concentration, mood changes, fatigue and sleepiness.
  • It passes, and most people fully recover.
  • If you think you've had a concussion, it's best to have it confirmed by a doctor as soon as possible.
Woman sits outside with head injury having fallen off bike
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A concussion is a type of mild traumatic brain injury (mTBI). It occurs when a bump, blow or shake to your head or body transmits a force to your brain. This does NOT cause any bleeding, bruising or swelling in the brain, the reason why scanning your brain is not helpful to diagnose concussion. However, it causes a change in the brains cells, essentially altering their function. This is due to chemical changes within the cell. To imagine this, think of these cell changes as a leak in a bag of water.

  • You don't have to get a blow directly to your head itself – impact anywhere on your body can transmit forces to your brain. 
  • You also don't have to be knocked out to get a concussion. In fact, loss of consciousness only happens with 10% of concussions.

Video: Concussion management and return to learn

The following video by Dr Mike Evans, on concussion management and return to learn, provides a useful summary of the key points to know. This video may take a few moments to load.

(Doc Mike Evans, US, 2015)

If you, or someone else, has had (or may have had) a concussion, it needs to be taken seriously. See your doctor as soon as possible.

Warning signs to watch for

The first 24 hours after having a brain injury are crucial. You should seek urgent medical help (either go to A&E or call 111 for an ambulance) if you or someone you are caring for:

  • has a headache that gets worse, that is not relieved with simple pain relief like paracetamol
  • is very sleepy or difficult to wake
  • is confused or doesn’t recognise you
  • has fits or seizures (repeated jerking movements of arms, legs or face)
  • has strange feelings or loss of movement down one side of the body
  • slurs their speech
  • has blurred vision bad enough to stop seeing properly
  • has double vision
  • is increasingly irritable or restless
  • vomits more than once
  • complains of neck pain
  • has behavioural changes
  • passes out.

See symptoms of concussion below.

Call Healthline free on 0800 611 116 if you don't know what to do.


  • Anyone who knocks their head (playing a sport or through a fight or accident) and gets up straight away, still needs to be closely watched as they may develop symptoms after the injury, usually within that day. If they show any of the warning signs above, they need to see a doctor as soon as possible. 
  • If they've been knocked out (become unconscious) they should see a doctor that day to make sure there's nothing more serious going on.

A concussion can happen to anyone. Common events causing concussion include:

  • Falls: These are the most common cause of concussion overall, particularly in older adults and young children.
  • Vehicle-related collisions: Collisions involving cars, motorcycles or bicycles – and pedestrians involved in such accidents.
  • Domestic violence: This, child abuse and other assaults are common causes.
  • Sports injuries: Concussions are a common type of sports injury. Higher risk sports for concussion include contact activities such as boxing, martial arts, contact sports. It can also occur in any sport with fast movement or balls (eg, cycling, equestrian activities, cricket, hockey, water polo, snow sports) but can occur across all sporting activities.

Symptoms of a concussion or mild traumatic brain injury (mTBI) may not be immediate. They may appear a few hours later but generally within 24–48 hours.  

Warning signs

The first 24 hours after having a brain injury are crucial. You should seek urgent medical help (either go to A&E or call 111 for an ambulance) if you or someone you are caring for shows any of the warning signs in the table above.

If you've had a concussion, or think you have, it needs to be taken seriously. See your doctor as soon as possible if you notice any of the following signs of concussion.

Physical symptoms Sensitivity to light, dizziness or 'seeing stars', excessive or unusual fatigue, headache, nausea and vomiting, blurry vision
Emotional Feeling particularly anxious, irritable, moody, or sad
Thinking and remembering  Having difficulty paying attention, feeling confused, memory problems, feeling foggy
Sleep Sleeping too much or too little, trouble falling asleep


If you're watching somebody else, here are some immediate signs of a concussion. They may:

  • lose consciousness – this doesn't have to happen for them to be concussed
  • appear dazed or confused
  • slur their speech
  • forget what happened 
  • ask the same question again
  • vomit (be sick)
  • lose their balance.

Not every sign and symptom will be present in every person and some may not appear for hours or days following a head injury.

Fortunately, these symptoms are usually temporary. But if you don't let your brain fully recover, you're at risk of:

  • further brain injury or concussion
  • musculo-skeletal injury (injury to your muscles or bones)
  • longer recovery time if you have a second concussion
  • second impact syndrome – when having a second concussion before you have fully recovered from the first leads to swelling of your brain.

If you get a concussion, you need to be seen by a doctor. The first 24 hours after the bump or blow are critical, as this is when serious complications are more likely to occur. It's really important you're not left alone and someone monitors how you're doing.

In the first 24 hours following your concussion:

  • Take relative rest – this means taking things easy and resting when you want. If you feel you need to sleep, make sure someone checks on you regularly in the first 4–6 hours.
  • Somebody needs to wake you gently every 2 hours (in the first 4–6 hours of sleeping) and ask you to answer a simple question. If you can’t be woken normally, then get medical help urgently.
  • Avoid alcohol, sleeping pills and illegal drugs – these can hide problems that might be developing.
  • Take paracetamol if needed for headache.
  • Don’t drive a motor vehicle.
  • Avoid physical activity.

Woman waking her partner after he's been concussed

Image credit: Canva


Most people with concussion recover with simple education and advice about controlled physical and mental activity. Your doctor will be able to provide you with this. It may include time away from work or school with a plan to gradually get you back to normal life.

If at any point your symptoms get worse, or if more serious symptoms develop (see the warning signs listed above) you should see a doctor straight away. 

If your symptoms continue for more than 2 weeks, see your doctor again. For people with ongoing symptoms, referral to a concussion service may be needed.

Apps reviewed by Healthify

You may find it useful to look at some Concussion apps and First aid and emergency apps.

If you've had a concussion, see a doctor and do NOT return to sports activities or work (where any further injury is a risk) before you have been cleared as safe to do so.

To prevent ongoing effects from a concussion, it's important that you've recovered before returning to recreational or competitive sports, or activities that could have a risk of a further head injury. Another head impact can result in brain swelling and bleeding – a more serious injury than concussion that can result in death. Although it's rare, this ‘second impact syndrome’ has been recognised.

Many adults recover from a concussion within 2 weeks, with 80% of people recovering within 4 weeks. For children and teenagers (under 18 years of age) recovery can take longer.

Some people have symptoms that will last longer. This is now known as persistent concussion symptoms. If your symptoms are not getting better, see your healthcare provider. 

To improve your recovery, follow these rules: 

  • Relative physical and mental rest is advised for the first 48 hours after the injury. After this, seek advice from your doctor about making a plan for a gradual return to normal activities.
  • Use your symptoms to guide you on how much to do – mentally and physically. Activity should be at a level that doesn't make your symptoms worse.
  • Avoid substances that negatively affect your brain, eg, alcohol and illegal substances/drugs.
  • Eat and sleep well.
  • If you play competitive sport:
    • you must be symptom free for 14 days before you return to training, and
    • you can't return to play for 21 days (3 weeks) after your injury
    • it's best to have your doctor give you clearance to return after this time period.
  • Ask your whānau and friends for support. They may also need to get some support to understand and help you with your recovery. 

Video: Interview: Shontayne Hape - Tackling the issue of Concussions in Rugby

Shontayne Hape (NZ rugby player) talks about his experience with concussion and how to stay safe on the field. This video may take a few moments to load.

(Sport360, AE, 2015)

Video: Rugby concussion 2 

This video may take a few moments to load.

(Peter Harold, NZ, 2018)

What is a brain injury?(external link) Brain Injury NZ
Resources for living with a brain injury(external link) Brain Injury NZ
Head injuries and concussion(external link) Health New Zealand | Te Whatu Ora
National guidelines for sport concussion [PDF, 117 KB] ACC, NZ
Concussion – not just for adults(external link) ACC, NZ
Concussion – symptoms, causes, diagnosis and treatment(external link) Healthline, US


Recovery advice Whakaora Tohutohu for patients(external link) Accident Compensation Corporation (ACC), NZ, 2022 English(external link), te reo Māori(external link)
Caring for your child after their head injury(external link) Accident Compensation Corporation (ACC), NZ
Fact sheet – concussion recovery(external link) Rugby Smart, NZ


SCAT6 Sports Concussion Assessment Tool(external link)
Concussion apps
First aid and emergency apps


  1. Concussion(external link) Mayo Clinic, US, 2024
  2. Feigin V, Theadom A, Barker-Collo S, et al. Incidence of traumatic brain injury in New Zealand – a population-based study(external link) Lancet Neurol. 2013;12(1), 53-64
  3. Patricios JS, Schneider KJ, Dvorak J, et al. Consensus statement on concussion in sport – the 6th International Conference on Concussion in Sport–Amsterdam, October 2022(external link) 


SPort concussion in NZ guidelines 2023

Sport concussion in New Zealand – national guidelines Accident Compensation Corporation (ACC), NZ, 2023

Recovery advice Whakaora Tohutohu for patients, Accident Compensation Corporation (ACC), NZ
English, te reo Māori

caring for your child after their head injury

Caring for your child after their head injury

Accident Compensation Corporation (ACC), NZ, 2022

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Credits: Healthify editorial team. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Dr Stephen Kara, Sport and Exercise Physician, Queenstown

Last reviewed: