Concussion: Complete Guide

What is Concussion?

A concussion is a mild traumatic brain injury (mTBI) caused by a blow to the head, face, neck, or body that transmits force to the brain. It can happen in sports, falls, car crashes, assaults, and everyday accidents. “Mild” describes the typical absence of life-threatening structural damage on standard imaging, not the impact on your life. Symptoms can be subtle, delayed, and highly individual.

A concussion is primarily a functional brain injury. Many people have normal CT or MRI scans, yet still experience real problems with attention, reaction time, light sensitivity, headaches, emotional regulation, or sleep. Symptoms often resolve within days to weeks, but some people have longer recoveries, especially after repeat concussions or when risk factors are present.

Concussions are common and frequently under-recognized. You do not need to be knocked out to have a concussion. In fact, most concussions occur without loss of consciousness.

> Key point: If a head or body impact is followed by new neurological symptoms (confusion, headache, dizziness, nausea, vision changes, memory gaps), treat it as a concussion until proven otherwise.

How Does Concussion Work?

Concussion is best understood as a biomechanical and metabolic injury. The brain is soft tissue suspended in cerebrospinal fluid. Rapid acceleration, deceleration, and rotation can cause the brain to move and deform within the skull.

The mechanics: acceleration, rotation, and “bounce”

A direct hit to the head is not required. A hard fall onto the hip or shoulder, or a whiplash-type event in a car crash, can transmit force to the brain. Rotational forces are particularly important because they strain axons and networks across multiple regions.

A classic teaching point is coup-contrecoup: injury can occur at the site of impact (coup) and on the opposite side (contrecoup) as the brain shifts. This helps explain why a single blow can produce symptoms that do not “match” the visible impact location.

This also connects to a major safety concept: the danger is not only how hard a hit looked, but how the brain moved inside the skull and whether a second hit occurs before recovery. (See our related article on why a second head hit can be more dangerous.)

The neurometabolic cascade

After injury, brain cells experience a temporary energy crisis:

• Mechanical deformation triggers ion shifts (potassium out, calcium in).
• The brain increases glucose demand to restore balance.
• Blood flow and energy delivery can be mismatched, creating a vulnerable period.
• Neurotransmitter changes can affect mood, sleep, and attention.

This is why early after a concussion you may feel “wired but tired,” foggy, irritable, or unusually sensitive to noise and light. It is also why repeat impact during this window can be disproportionately harmful.

Network disruption, not just one spot

Concussion symptoms often reflect disrupted communication across brain networks:

• Vestibular system (balance, motion sensitivity)
• Oculomotor system (eye tracking, convergence, visual motion)
• Autonomic nervous system (heart rate, dizziness, exercise intolerance)
• Sleep-wake regulation (insomnia, hypersomnia)

Because multiple systems can be involved, recovery is often fastest when care is symptom-guided and targeted, rather than “wait and hope.”

Benefits of Concussion

A concussion is an injury, so it is not something to seek. However, there are real, evidence-aligned “benefits” in the sense of adaptive outcomes that can come from proper recognition and management. These are not guaranteed, and they do not justify risk-taking, but they matter for framing recovery.

Earlier detection of serious brain or neck injury

Treating a suspected concussion seriously can lead to faster identification of red flags such as intracranial bleeding, cervical spine injury, or worsening neurological status. In practice, “concussion protocols” save lives by creating a structured pathway to recognize when something is more than a concussion.

A forcing function for safer behavior and prevention

A diagnosed concussion often prompts:

• Better helmet fit and sport technique changes
• Reduced risk-taking and improved situational awareness
• Team or workplace safety improvements
• Education for family members and coaches

This prevention effect is especially relevant for youth sports and high-risk activities, where repeat impacts are common.

Opportunity to address treatable contributors

Persistent symptoms are often worsened by modifiable factors such as poor sleep, dehydration, migraine tendency, neck strain, anxiety, or vestibular dysfunction. A concussion evaluation can uncover these and lead to targeted therapy.

> Reframe: The “benefit” is not the concussion. The benefit is what happens when you recognize it early and respond well.

Potential Risks and Side Effects

Concussion risk is not only about the initial injury. It is also about what happens in the hours, days, and weeks afterward.

Short-term risks

Common symptoms (minutes to days):

• Headache or head pressure
• Dizziness, balance problems
• Nausea or vomiting
• Sensitivity to light or noise
• Brain fog, slowed processing
• Memory gaps around the event
• Irritability, anxiety, low mood
• Sleep disruption

Functional risks:

• Slower reaction time increases risk of falls, car crashes, and repeat injury.
• Impaired judgment can lead to returning to play or work too soon.

Serious red flags: seek urgent or emergency care

Go to urgent care or the emergency department immediately if any of these occur after a head injury:

• Worsening headache, repeated vomiting, or increasing confusion
• Seizure, fainting, or severe drowsiness that is hard to wake
• Weakness, numbness, slurred speech, unequal pupils
• Neck pain with neurological symptoms
• Behavior changes that are extreme or escalating
• Any symptom that is rapidly worsening

Also seek urgent evaluation if the person is:

• On blood thinners or has a bleeding disorder
• Very young, older, or medically fragile
• Suspected of having a skull fracture

Second impact and repeat injury

A second head hit before recovery can be far more dangerous than it appears. Even a “lighter” impact can cause disproportionate symptoms and prolong recovery. Rarely, catastrophic brain swelling has been described in the context of rapid repeat injury (often discussed as second impact syndrome). The practical takeaway is simple: avoid repeat contact until fully cleared.

Prolonged recovery and persistent post-concussion symptoms

Some people develop symptoms lasting longer than expected. Factors associated with longer recovery include:

• Prior concussions, especially multiple or recent
• Migraine history
• Vestibular or vision problems
• High early symptom burden
• Poor sleep or untreated sleep disorders
• Anxiety, depression, or high stress
• Returning to intense activity too soon

Persistent symptoms are real and treatable, but they often require active rehab rather than indefinite rest.

Long-term concerns and uncertainty

Repeated head impacts are associated with increased risk of long-term cognitive and mood problems in some populations. Research on chronic traumatic encephalopathy (CTE) continues to evolve. What is clear is that repetitive head impacts and multiple concussions increase risk, and prevention plus appropriate recovery time matters.

Practical: What to Do After a Concussion (Best Practices)

This is the section most people need: what to do now, what to avoid, and how to return to normal life safely.

Step 1: Immediate actions (first minutes to 24 hours)

1. Remove from risk: Stop play, stop riding, stop working at heights or with machinery. 2. Check for red flags: If present, seek emergency care. 3. Do not “test it” by continuing activity to see if symptoms worsen. 4. Have someone stay with you for the first several hours if possible.

About imaging: CT scans are used to rule out bleeding or fracture when clinically indicated. A normal CT does not rule out concussion.

> Callout: If symptoms are getting worse, not just lingering, treat that as urgent.

Step 2: The first 24 to 48 hours: relative rest, not “dark room”

Modern concussion care favors relative rest for the first day or two:

• Reduce physical exertion that worsens symptoms.
• Reduce intense cognitive load (long exams, complex work bursts) if it spikes symptoms.
• Light daily activity is usually fine if it does not significantly worsen symptoms.

Avoid:

• Alcohol and recreational drugs
• High-risk activities (sports, cycling, ladders)
• Prolonged symptom-provoking screen use if it clearly worsens symptoms

Step 3: Gradual return to activity (symptom-guided)

After the first 24 to 48 hours, most people do better with gradual, sub-symptom-threshold activity.

#### Return to learn / return to work A practical approach:

• Short blocks of reading or computer work with breaks
• Temporary adjustments: reduced workload, extra time, quiet workspace, reduced bright light
• Progress weekly or faster depending on symptoms

If symptoms spike, reduce intensity and try again later. The goal is steady progress, not pushing through.

#### Return to exercise Light aerobic activity can support recovery when done below the symptom threshold. Examples:

• Walking
• Easy stationary cycling
• Light jogging only when symptom-free with walking

Stop and scale back if symptoms rise meaningfully during or after.

#### Return to sport (stepwise progression) Most sports protocols use staged progression, typically: 1. Symptom-limited activity 2. Light aerobic exercise 3. Sport-specific exercise without contact 4. Non-contact training drills with higher intensity 5. Full contact practice after medical clearance 6. Return to competition

Progression is individualized. Many programs require at least 24 hours between stages and no symptom worsening.

Step 4: Targeted treatment for common symptom drivers

If symptoms persist beyond about 10 to 14 days in adults, or 4 weeks in children, consider a concussion-aware clinician and targeted rehab.

Common targeted treatments include:

• Vestibular therapy for dizziness and motion sensitivity
• Vision therapy for convergence insufficiency and tracking issues
• Cervical spine physical therapy for neck-driven headaches and dizziness
• Sub-threshold aerobic training guided by symptom response
• Migraine-style headache management if headaches have migrainous features
• Sleep interventions (consistent schedule, light exposure timing, CBT-I when needed)

Hydration, nutrition, and sleep: supportive basics that matter

Recovery is a stress test for your body. Hydration and adequate calories help support sleep, blood pressure stability, and headache control.

• Aim for pale-yellow urine most of the day.
• Increase fluids if you are vomiting, sweating, or not eating well.
• If you cannot keep fluids down, feel faint, or show signs of dehydration, seek care. (See our hydration lessons article for practical guidance on when oral fluids are not enough.)

Sleep is often the strongest recovery lever:

• Keep a consistent wake time.
• Limit long naps that steal nighttime sleep.
• Reduce evening caffeine.

Medications: practical cautions

Medication choices depend on timing and individual risk.

• For headaches, clinicians often start with acetaminophen early, then consider NSAIDs later if bleeding risk is not a concern.
• Avoid sedating medications unless prescribed, since they can mask worsening symptoms.
• Do not start supplements or nootropics expecting a “brain healing shortcut.” Evidence is mixed and quality varies.

Always follow clinician guidance, especially if you have other medical conditions or take blood thinners.

What the Research Says

Concussion research has advanced significantly in the last decade, with ongoing updates through consensus statements and clinical guidelines. Several themes are well supported.

1) Early, strict rest is not superior to relative rest

Older advice often recommended prolonged “cocooning” in a dark room. Current evidence supports brief relative rest followed by gradual activity as tolerated. Too much rest can worsen sleep, mood, conditioning, and symptom focus.

2) Sub-symptom aerobic exercise can speed recovery for many

Randomized trials and sports medicine protocols support individualized, sub-threshold aerobic exercise as part of rehabilitation, particularly for persistent symptoms and autonomic dysfunction (exercise intolerance).

3) Persistent symptoms are often multi-factorial and treatable

Research supports targeted therapies for:

• Vestibular dysfunction
• Oculomotor deficits
• Cervicogenic contributors
• Migraine phenotypes
• Sleep and mood contributors

The best outcomes often come from matching treatment to the dominant symptom drivers rather than using a one-size-fits-all approach.

4) Biomarkers and imaging are promising but not routine

Advanced MRI techniques, blood biomarkers, and digital neurocognitive tools are improving understanding and may help in the future. In routine care, diagnosis remains clinical, based on history, symptom patterns, exam, and risk assessment.

5) Youth require extra caution

Children and adolescents often take longer to recover and face higher risk from premature return to contact. Research supports structured return-to-learn plans and conservative return-to-play timelines.

What we still do not know

• Exactly why some individuals develop prolonged symptoms after seemingly similar injuries
• The precise dose-response relationship between repetitive sub-concussive impacts and long-term outcomes
• Which biomarkers will reliably guide individualized clearance decisions

Evidence quality varies by topic, but overall, the trend is toward active, individualized rehabilitation and strong prevention of repeat injury.

Who Should Consider Concussion Evaluation and Management?

Concussion care is not only for athletes. Anyone with a compatible mechanism and symptoms should consider evaluation.

People who should be evaluated promptly

• Anyone with red flags (worsening headache, repeated vomiting, confusion, neurological deficits)
• Anyone with symptoms that interfere with daily function (work, school, driving)
• Children and teens with suspected concussion
• People with prior concussions, migraines, learning disorders, ADHD, or mental health conditions
• Older adults after a fall, especially if on anticoagulants

People who often benefit from specialized concussion clinics

• Symptoms persisting beyond expected recovery windows
• Significant dizziness, balance issues, or visual symptoms
• Complex return-to-work or return-to-sport decisions
• Co-existing neck injury, migraine, or sleep disorder

High-risk groups where prevention matters most

• Contact and collision sport athletes
• Cyclists, skiers, and riders in high-speed sports
• Workers in construction, policing, military, and transportation

Our sports tier-list article can help you think clearly about which activities carry the highest nervous system risk and how to reduce it.

Common Mistakes, Related Issues, and Safer Alternatives

Mistake 1: Judging severity by how hard the hit looked

A “minor” looking hit can still cause significant brain movement, especially with rotation. Conversely, a dramatic hit does not always produce severe symptoms. Go by symptoms and function, not appearance.

Mistake 2: Returning to play or risky activity too soon

This is the most preventable cause of prolonged recovery and repeat injury. If you are still symptomatic, your reaction time and balance may be impaired.

> Callout: The most dangerous concussion is often the one followed by another hit before recovery.

Mistake 3: Total inactivity for too long

Prolonged bed rest can worsen sleep, mood, and conditioning. Your body is built to move, and long inactivity can cause rapid deconditioning. Gentle movement, as tolerated, usually helps. (Related: our article on how quickly the body breaks down with not moving.)

Mistake 4: Ignoring the neck

Neck strain can mimic or amplify concussion symptoms, especially headache and dizziness. If symptoms persist, assessment of the cervical spine is often essential.

Mistake 5: Treating “brain fog” as purely psychological

Mood and stress can amplify symptoms, but that does not mean symptoms are imagined. A good plan addresses physiology (sleep, vestibular, vision, exercise tolerance) and psychology (stress, coping skills) together.

Related conditions that can overlap

• Migraine and post-traumatic headache
• Benign paroxysmal positional vertigo (BPPV)
• Cervicogenic dizziness
• Anxiety and panic symptoms
• Sleep disorders

A clinician can help differentiate these because treatments differ.

Frequently Asked Questions

How long does a concussion last?

Many adults improve substantially within 7 to 14 days, and many children within 2 to 4 weeks, but timelines vary. Early symptom burden, prior concussions, migraine history, and sleep issues can prolong recovery.

Do you need to lose consciousness to have a concussion?

No. Most concussions occur without loss of consciousness. Confusion, memory gaps, dizziness, or headache after an impact can be enough.

Should you wake someone up after a concussion?

If a clinician has ruled out serious injury and the person is stable, normal sleep is usually fine. In the first hours, monitoring for worsening symptoms is important. Follow local medical advice and seek urgent care if symptoms worsen.

Can you drive with a concussion?

Often you should avoid driving until you can concentrate without symptom spikes and your reaction time feels normal. Dizziness, light sensitivity, and slowed processing can make driving unsafe.

What helps concussion recovery the most?

After brief relative rest, the biggest levers are symptom-guided activity, good sleep, hydration and nutrition, and targeted therapy for vestibular, vision, neck, or migraine contributors when present.

How many concussions are too many?

There is no universal number. Risk depends on severity, recovery time, spacing between injuries, and individual vulnerability. Repeat concussions with longer recoveries or less force causing symptoms are warning signs to reassess exposure and consider reducing contact risk.

Key Takeaways

• A concussion is a mild traumatic brain injury caused by forces transmitted to the brain, often without loss of consciousness.
• Symptoms reflect a temporary metabolic and network disruption, not always visible on standard imaging.
• Red flags like worsening headache, repeated vomiting, confusion, seizures, or neurological deficits require urgent evaluation.
• The highest preventable risk is repeat injury before recovery. Do not return to contact or risky activity too soon.
• Best practice is 24 to 48 hours of relative rest, then gradual, symptom-guided return to school, work, and exercise.
• Persistent symptoms are often treatable with targeted rehab (vestibular, vision, neck therapy, migraine and sleep management).
• Hydration, sleep, and gentle movement support recovery, while prolonged inactivity can slow it.