Concussion

What it is

How the consensus statement defines it

The Concussion in Sport Group defines sport-related concussion, in part, as a traumatic brain injury^1,2,3. In that definition, a direct blow to the head, the neck or the body passes a sudden force to the brain during sport or exercise^1,2,3. Symptoms and signs may show at once or develop over minutes or hours^1,2,3.

A consensus statement is a report that sets out what a panel of experts agrees on. The 6th international consensus statement on concussion in sport summarises a conference held in Amsterdam in October 2022⁶. Ten systematic reviews, which author groups carried out over three and a half years, informed it⁶. A systematic review is a study that searches for all the research on a question in a set, checkable way and sums it up. This page calls the document the 2022 Amsterdam statement.

The 2022 Amsterdam statement describes a sport-related concussion in these terms⁶:

• In the brain. It defines the injury as starting a neurotransmitter and metabolic cascade in the brain⁶. Axon injury, blood flow change and inflammation are possible⁶. An axon is a nerve fibre, the long thread of a nerve cell that carries its signals.
• On scans. No abnormality is seen on standard structural brain imaging, meaning CT or standard MRI⁶. CT builds detailed pictures of the inside of the body from X-rays, and MRI shows soft tissue in detail.
• Consciousness. Loss of consciousness may or may not be among the symptoms and signs⁶.
• Time course. The symptoms and signs commonly clear within days, but may last longer⁶.

A 2025 consensus extension statement describes the symptom clusters of sport-related concussion¹. They include headache, dizziness, balance problems, and cognitive (thinking), emotional and sleep disorders¹.

In a 2023 expert consensus process on mild traumatic brain injury (TBI), 30 of 32 panel members agreed on how two labels relate⁷. They agreed that the labels “concussion” and “mild TBI” may be used interchangeably when brain imaging is normal or not clinically indicated⁷.

What a recognition tool lists

A 2024 comparison of concussion guidelines tabulates the head or spine injury “red flags” listed in the Concussion Recognition Tool 6⁸. The list is reported here as what that tool contains. It is not a checklist for readers, and this page gives no advice.

The tool lists neck pain or tenderness, a seizure, fit or convulsion, and loss of vision or double vision⁸. It lists loss of consciousness, increased confusion or a deteriorating conscious state, repeated vomiting, and a severe or increasing headache⁸. It also lists weakness, tingling or burning in the legs or in more than one arm⁸. The last two are increasing restlessness, agitation or combativeness, and visible deformity of the skull⁸.

Who it affects

United States college sport

Injury surveillance data from 25 United States college (NCAA) sports cover the 2009–2010 to 2013–2014 academic years⁴. The data recorded 1,670 sports-related concussions, an overall rate of 4.47 per 10,000 athlete-exposures⁴. Four of the 25 sports had the largest rates⁴:

Sport	Concussions per 10,000 athlete-exposures
Men’s wrestling	10.924
Men’s ice hockey	7.914
Women’s ice hockey	7.504
Men’s football	6.714

The same data show when and how these concussions happened⁴:

• Setting. The rate was about five times higher in competition than in practice, 12.81 against 2.57 per 10,000 athlete-exposures⁴.
• Mechanism. Most of the 1,670 concussions, 68.0%, occurred from player contact⁴.
• Repeats. Of the 1,670 concussions, 9.0% were recurrent⁴.

School-age athletes

A surveillance study of 20 high school sports from 2013–2014 to 2017–2018 recorded 9,542 concussions⁹. The overall rate was 4.17 per 10,000 athlete-exposures, and football had the highest rate, 10.40⁹.

Rugby

A 2026 systematic review and meta-analysis of 98 studies covered 10,591 concussions in rugby¹⁰. Pooled incidence was 9.74 per 1,000 player-hours in rugby union and 9.20 in rugby league¹⁰. Incidence is how many new cases appear in a group over a set time. Player-hours are the hours each player spends in play, added together. In rugby union, incidence was 10.98 per 1,000 match-player-hours against 0.34 per 1,000 training-player-hours¹⁰.

Sex and earlier concussions

A systematic review with meta-analysis of 38 studies compared females with males¹¹. Incidence was higher in females in soccer (rate ratio 1.76) and basketball (1.99)¹¹. A rate ratio is one group’s rate of an event divided by the other group’s. Differences were not statistically significant in baseball and softball, ice hockey, lacrosse, swimming and diving, or track and field¹¹.

A 2014 systematic review of 86 articles on risk factors for sports concussion gave a high level of certainty to two¹². One was more than one previous concussion, in 10 of 13 studies, and the other was match play, in each of 29 studies¹². It rated the other risk factors as having a low level of certainty¹².

What studies found

How long recovery took

A systematic review and meta-analysis pooled 278 studies of sport-related concussion⁵. Of these, 80.6% were cohort studies and 92.8% came from North America⁵. It reported three mean times⁵:

Milestone	Mean days
Return to school or learning	8.3 days5
Symptom free	14.0 days5
Return to sport	19.8 days5

By 10 days, 93% of athletes had fully returned to learning without new academic support⁵. The return-to-sport figure came with high heterogeneity, which is how much the results of the pooled studies differ from one another⁵.

A 2025 consensus extension statement gives the typical time for symptoms to resolve as 1 to 4 weeks¹. It describes persistent postconcussion symptoms as symptoms that continue beyond 4 weeks after injury, occurring in 8–35% of cases¹.

What went with slower recovery

Three systematic reviews report these links^5,13,14:

• Early symptoms. A 2017 systematic review of 101 articles found the most consistent predictor of slower recovery was how severe a person’s acute and subacute symptoms were¹³. In the 278-study review, initial symptom burden remained the strongest predictor of more days until return to sport⁵.
• Playing on. The 278-study review found that playing on was associated with longer recovery, and so was delayed access to healthcare providers⁵.
• Sleep. A 2023 systematic review found sleep disturbance was associated with slower recovery after sport-related concussion¹⁴.

What the consensus statement says about rest

This section and the staged-return section below report what published statements say. They describe that guidance and are not advice. The 2022 Amsterdam statement says that, on the best evidence available, recommending strict rest until symptoms have fully resolved is not beneficial⁶. It says health care professionals should avoid prescribing absolute rest, both physical and cognitive, which it calls “cocooning”⁶.

The statement describes the first two days this way⁶:

• Relative rest. It says relative rest is indicated from the start, for up to 2 days after injury⁶. Relative rest, in the statement, includes daily living activities and less screen time⁶.
• Light activity. It says individuals can return to light physical activity, such as walking, during the first 24 to 48 hours⁶. This is activity that does not more than mildly worsen symptoms⁶.
• Screens. It says the best data show reduced screen use is warranted in the first 48 hours, but may not be effective beyond that⁶.

What trials of rest and exercise found

In a randomised trial, 99 patients aged 11 to 22 were seen in a children’s emergency department within 24 hours of concussion¹⁵. A randomised trial assigns people to groups by chance, then compares the groups. Those assigned to strict rest for 5 days reported more daily symptoms over 10 days, and slower symptom resolution, than those given usual care¹⁵. Usual care was 1–2 days of rest followed by a stepwise return to activity¹⁵. Neurocognitive (thinking test) and balance outcomes showed no clinically significant difference between the groups¹⁵.

Two randomised trials enrolled adolescent athletes aged 13–18 seen within 10 days of a sport-related concussion^16,17:

• 103 athletes. Those assigned to aerobic exercise below the level that worsened symptoms recovered in a median of 13 days, against 17 days for a stretching programme¹⁶. The median is the middle value when a set of numbers is lined up from smallest to largest.
• 118 athletes. The group assigned to individualised aerobic exercise was more likely than the group assigned to stretching to recover within 4 weeks¹⁷. Their risk of persistent symptoms was 48% lower, and no adverse events (unwanted effects seen during a trial) were reported¹⁷.

A 2023 systematic review of 46 studies covered the first 14 days after sport-related concussion¹⁴. In its meta-analysis of seven studies, recovery improved by a mean of 4.64 days with physical activity and prescribed exercise¹⁴.

The staged return the statements describe

The passages below report the content of published statements. They are not a programme for readers and not advice. A 2024 comparison of concussion guidance in Irish sport lists the six stages of the Concussion in Sport Group’s graduated return-to-play pathway⁸:

1. Symptom-limited activity⁸.
2. Aerobic exercise⁸.
3. Individual sport-specific exercise⁸.
4. Non-contact training drills⁸.
5. Full-contact practice⁸.
6. Return to sport⁸.

The 2022 Amsterdam statement says a minimum of 1 week can be expected to complete the full return-to-sport strategy⁶. It says typical unrestricted return to sport can take up to 1 month⁶. It says a health care professional should monitor progression through the later steps, Steps 4 to 6⁶.

A 2025 consensus extension statement reports a recommendation of the Concussion in Sport Group¹. The group recommends medical clearance before an athlete moves on from moderate aerobic exercise to individual sport-specific exercise¹. That is exercise which may carry a risk of inadvertent head impact¹.

On school, the 2022 Amsterdam statement says a return-to-learn strategy can begin after an initial 24 to 48 hours of relative rest⁶. It says return to learning and return to sport can run in parallel⁶. Student-athletes, it says, should complete full return to learning before unrestricted return to sport⁶.

Repeat concussions

In a prospective cohort study of 2,905 United States college football players, 184 (6.3%) had a concussion during follow-up¹⁸. Players reporting three or more previous concussions were 3.0 times more likely to have one than players with no concussion history¹⁸. In that 1999–2001 study, 12 of the 184 concussed players (6.5%) had a repeat concussion in the same season¹⁸. Eleven of those 12 repeats came within 10 days of the first injury¹⁸.

A 2025 consensus extension statement describes second impact syndrome as rare, with mixed definitions in the literature¹. It may follow a second head trauma that comes before an existing concussion has fully resolved¹. The authors of a systematic review of 91 sources wrote that the syndrome’s actual mortality rate is unknown¹⁹.

Rule changes and equipment

A systematic review and meta-analysis of prevention strategies for sport-related concussion had 192 studies in its results²⁰. It reported three associations²⁰:

• Bodychecking. In child and adolescent ice hockey, a policy disallowing bodychecking was associated with a concussion rate 58% lower than in leagues that allowed it²⁰.
• Contact in practice. Strategies that limited contact in American football practices were associated with a practice-related concussion rate 64% lower²⁰.
• Mouthguards. Concussion rates were lower with mouthguard use in collision sports, with an incidence rate ratio of 0.74²⁰.

Later life

A systematic review covered 10 studies of former amateur athletes and 18 of former professional athletes²¹. For former amateur athletes exposed to repetitive head impacts, it concluded the evidence does not support a raised risk of mental health or neurological diseases²¹. Some of its studies of former professional athletes suggest a raised risk of neurological disorders such as dementia²¹. The authors said those findings need confirming in higher-quality studies with better control of confounding factors, meaning other factors that could explain a link²¹.

Connections

The neck

The authors of the prevention review named neck strength and optimal tackle technique as potentially modifiable risk factors that need more research²⁰. Studies of neck strength and concussion point different ways, and the neck isometric hold page covers them at more length^22,23. In 6,704 high school soccer, basketball and lacrosse athletes, weaker overall neck strength was associated with concussion²². A meta-analysis of eight studies in 7,625 team-sport athletes found a small, non-significant relationship between greater neck strength and lower concussion risk²³. It rated that evidence as very low certainty²³.

Neck pain or tenderness is among the red flags the Concussion Recognition Tool 6 lists, as reported in a 2024 comparison of guidelines⁸. Neck symptoms themselves are covered on the neck pain and whiplash pages.

Sources

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Every source the library cites

Changes

• October 9, 2026 First published.