What is a Concussion?

A concussion is a mild traumatic brain injury caused by a biomechanical force, whether from a direct blow to the head or a hit elsewhere on the body that transmits force to the head. Current international consensus guidelines describe it as a complex process driven by changes in brain cell metabolism rather than visible structural damage.

Read more: What Happens If You Hit Your Head Hard?

That distinction matters clinically: a standard CT scan or MRI will usually look normal after a concussion, even though the person is genuinely injured. Diagnosis relies on a clinical exam, a description of how the injury happened, and standardized symptom checklists, not imaging alone.

A person does not need to lose consciousness to have a concussion; most people with concussion never black out. Symptoms can begin immediately or take hours, even a day or two, to fully appear. They typically evolve over the first 72 hours after injury.

Good to know

• Loss of consciousness happens in a minority of concussions.
• Normal CT/MRI results do not rule out a concussion.
• Children and adolescents are assessed with pediatric-specific tools, having recovery heavily depend on academic functioning and physical activity tolerance.
• A repeat head injury before the brain has healed will typically delay recovery.

Signs and Symptoms

Modern clinical guidelines group concussion symptoms into four domains. Most people experience symptoms from more than one category, and the mix is different for everyone. Many symptoms may be new. However, other symptoms can overlap with pre-existing conditions, such as anxiety, depression, ADHD, migraines, etc., which is one reason a full clinical evaluation matters.

Emergency Red Flags, Don’t Wait!

Most concussions are managed safely without a hospital visit. However, some signs can indicate a more severe injury, warranting a medical emergency. Call 911 or go to the nearest emergency department right away if you notice any of the following after a bump, blow, or jolt to the head or body within the first 24-48 hours from injury:

• Loss of consciousness, even briefly
• Severe headache that keeps getting worse
• Repeated vomiting
• Seizure or convulsion
• Increasing confusion, agitation, or restlessness
• Slurred speech
• Weakness, numbness, or tingling in the arms or legs
• Persistent double vision or loss of vision
• Unequal or dilated pupils
• Severe or worsening neck pain
• Any visible deformity of the skull

These red flags come from CDC HEADS UP guidance and are corroborated by pediatric and adult emergency decision rules (PECARN, Canadian CT Head Rule) and the current Sport Concussion Assessment Tool (SCAT6) neurological screen. When in doubt, get it checked out.

Recovering from a Concussion

Current international consensus no longer recommends strict rest until every symptom disappears. A short rest period within 48 hours from injury is generally recommended followed by a supervised, gradual return to activity. Latest research has even shown supervised, light physical activity within 48 hours may lead to a faster recovery.

Preventing further injury is a primary concern following a concussion. Repeated impact to the head before full healing may worsen symptoms and further delay recovery. Thus early assessment, diagnosis, and treatment from a concussion specialist is essential to minimizing complications and optimizing recovery.

Important Steps for Recovery:

• Sleep
  • After a concussion, your brain depends on overnight sleep to flush out toxic proteins, calm inflammation, and repair damaged neural connections. However, the injury itself disrupts the very sleep your brain needs to heal and thus may prolong recovery. Protecting your sleep, especially in the first days and weeks after injury, is an essential part of your brain’s recovery process. Sleep hygiene techniques help to develop consistent sleep routines and facilitate improved sleep quality and duration.
• Physical Activity
  • Research strongly supports gradually reintroducing light aerobic exercise at an intensity that does not significantly worsen your symptoms in order to facilitate progressive recovery. Individualized guidance from a concussion specialist is essential for safely advancing through non-contact physical activity in a controlled manner until baseline tolerance is achieved.
• Stress Management
  • A concussion elevates stress hormones that can worsen symptoms and slow down recovery. Whether getting back to school, sport, or work, using accommodations are key for recovery, and implementing them into school or work can be half the battle. Clear communication with teachers or employers is important to ensuring their use and minimizing stress so you can manage symptoms without falling behind in school or work. Additionally, stress management techniques, such as cognitive behavioral strategies or mindfulness-based approaches, have been shown to reduce anxiety, depression, and post-concussion symptoms while supporting neurological recovery.
• Nutrition
  • Proper nutrition is essential to fuel the repair process in the brain following a concussion. While you may experience less appetite, meeting calorie and protein needs through a well-balanced diet facilitates better recovery. Avoid high-processed, sugary foods.
• Hydration
  • Dehydration can worsen headaches, dizziness, and fogginess. Maintaining adequate hydration supports blood flow to the brain, helping it to better recover. Drink water consistently throughout the day (not waiting until you feel thirsty), monitor urine color (pale yellow indicates proper hydration), and incorporate water-rich foods like fruits and vegetables. Electrolyte-containing beverages that are low-sugar can be helpful if you are sweating or struggling to maintain normal intake.