Overview
A concussion is a mild traumatic brain injury caused by a bump, blow, or jolt to the head that causes the brain to move rapidly inside the skull. It alters brain function temporarily. Most people recover fully within weeks, but repeated concussions can have lasting effects.
How common is it?
Concussion can happen in sport, falls, road accidents and other injuries. It can be missed because loss of consciousness is not required and symptoms may appear later.
Causes and risk factors
The sudden movement of the brain inside the skull stretches and damages nerve fibres and disrupts brain chemistry. A direct blow to the head is not required as violent shaking of the head can cause it too.
Common risk factors
- Contact sports (rugby, boxing, football, hockey)
- Falls, especially in the elderly
- Road traffic accidents
- Previous concussion (increases sensitivity to further injury)
- Female sex (some evidence of greater susceptibility)
- Young age (developing brains more vulnerable)
Symptoms
- Headache
- Dizziness or feeling 'foggy'
- Confusion or feeling slowed down
- Nausea or vomiting
- Blurred or double vision
- Balance problems
- Brief loss of consciousness (not always present)
- Memory problems around the time of injury
- Sensitivity to light and noise
- Sleep disturbance
When to see a doctor
Call emergency services (999 in the UK) after a head injury if the person remains unconscious, cannot stay awake, has a seizure, develops weakness or problems speaking or walking, or has a serious high-speed injury. Do not wait to see whether prolonged unconsciousness develops. Seek urgent advice for vomiting, dizziness, concerning symptoms, or use of blood-thinning medicine. Do not drive yourself for assessment.
Diagnosis
Concussion is diagnosed clinically. CT scan is used to rule out brain bleeding in patients with red flag symptoms. Neuropsychological testing assesses cognitive impact in athletes and those with prolonged symptoms.
Treatments
Brief relative rest, then gradual activity
Use relative rest for the first 24 to 48 hours, then gradually resume light activity such as short walks, as tolerated. Reduce activity if symptoms worsen. Avoid activities risking another head injury and follow clinical advice on returning to work, school, driving and sport.
Symptomatic management
Paracetamol may help headache if suitable; ask a clinician about other pain medicines after a head injury. Keep a regular sleep routine and avoid alcohol during recovery. Limit screens if they worsen symptoms, particularly before bed, rather than avoiding all screens throughout recovery.
Rehabilitation
Physiotherapy, vestibular rehabilitation, and neuropsychological support for people with persistent post-concussion symptoms lasting more than 4 to 6 weeks.
Self-care and lifestyle
- Follow the graduated return-to-sport protocol strictly after concussion in sport
- Never return to play on the same day as a head injury
- Wear appropriate helmets for cycling, skiing, and contact sports
- Report all head injuries to coaches, parents, or medics even if they seem minor
Prevention
Use appropriate protective equipment, seat belts and safe sporting practices. Helmets help protect against serious head injury but do not make concussion impossible. Concussion protocols and avoiding further head impacts during recovery are important.
Sources for targeted updates
Updated: 24 October 2026. Targeted corrections to frequency, treatment, prevention, key facts. This update covers the named sections; a full review of the remaining guide is pending.