A concussion, also called a brain concussion, is a change in mental status from trauma, often a blow to the head or a sudden jolt or shaking of the head. A concussion can cause confusion, disorientation, and amnesia (memory loss). Severe cases can cause loss of consciousness. Concussions, a type of traumatic brain injury (TBI), frequently occur when individuals are participating in sports or recreational events, especially if the activity involves full contact, such as in college or professional football, soccer, and hockey. Whether playing in athletic events to stay fit, getting into a car accident, or performing any high-impact activity, concussions cause a substantial number of deaths and permanent disabilities each year, resulting in a serious public health problem in the United States.


A concussion occurs when the head hits or is hit by an object or when the brain is jarred against the skull with sufficient force to cause temporary loss of function in the higher centers of the brain. The injured person might remain conscious or lose consciousness briefly and may be disoriented for some minutes after the blow. A TBI can be mild, with only a brief disruption in mental state or consciousness, or severe, with a lengthy period of unconsciousness followed by amnesia and other alterations of mental status.

Although a concussion usually improves on its own without any lasting effect, it can set the stage for a much more serious condition. Second impact syndrome occurs when a person with a concussion, even a very mild one, suffers a second blow before fully recovering from the first. The brain swelling and increased intracranial pressure that can result may be fatal. Numerous such cases have been reported since the syndrome was first described in 1984. Fitness, sports, and exercise experts are becoming more concerned about concussions as a serious problem that may occur during physical activities.


The incidence of concussions is estimated to be 2 per 1,000 individuals per year in the United States, with most of these reported injuries receiving medical attention. About three-quarters of TBIs that occur annually in the United States are concussions or other types of mild TBIs. Although most of these concussions are mild and do not cause any permanent injury or health concerns, about 10% cause disability or death.

Statistics collected by the Centers for Disease Control and Prevention (CDC) between 2001 and 2010 showed that on average more than 1.7 million people suffer a concussion annually. Traumatic brain injuries increased in number from 521 per 100,000 people in 2001 to 823.7 per 100,000 in 2010. The CDC also reports that TBIs are contributing factors in about one-third of all injury-related deaths in the United States each year. More than 300,000 sports-related concussions that result in unconsciousness occur each year in the United States. Still, less than 10% of sports-related concussions involve loss of consciousness, and as many as 5% to 10% of athletes get a concussion per sport season. The CDC admits that the true number is probably higher than figures suggest due to underreporting. Concussion rates among U.S. children doubled between 2007 and 2014.

Causes and symptoms


Playing contact sports is a risk factor for experiencing one or more concussions. As many as 3.8 million athletes have a concussion each year, according to the Brain Trauma Foundation. Most that occur are thought to be unreported. This is largely due to athletes not wanting to be medically disqualified from continuing to play their sport. Most sports-related brain injuries occur in young men between the ages of 16 and 25 years. Sports or fitness activities with high incidences of concussions include football, hockey, soccer, and cycling.

A doctor tests a football player for concussion. Playing contact sports, like football, puts athletes at a higher risk for this form of head injury. The problem was brought to light in the 2015 film Concussion, starring Will Smith.

A doctor tests a football player for concussion. Playing contact sports, like football, puts athletes at a higher risk for this form of head injury. The problem was brought to light in the 2015 film Concussion, starring Will Smith.
(Rocketclips, Inc./

The risk of concussion from football is extremely high, especially at the high school level. Studies show that approximately one in five players suffer a concussion or more serious brain injury during their brief highschool careers. The rate at the collegiate level is approximately one in 20. Rates for hockey players are less clear, but are believed to be similar. In general, football carries a high 75% risk for male athletes, and soccer is the highest concussion-related sport for girls and women (50% chance). Concussions occur not just during competition but also during practices. The number of diagnosed concussions in National Football League (NFL) players continues to rise, partly because of an emphasis on concussion protocols to keep players with concussions out of competition until it is safe to return. In 2015, 271 concussions were reported in NFL players. A 2009 study found that memory problems within former NFL players, such as Alzheimer's disease and other types of dementia, were 19 times more prevalent than in the average male population 30 to 49 years of age.

Concussion and lasting brain damage is an especially significant risk for boxers, because the goal of the sport is to deliver a knockout blow to the opponent. For this reason, the American Academy of Neurology and other such organizations have called for a ban on boxing. Repeated concussions over months or years can cause cumulative head injury. The cumulative brain injuries experienced by most boxers can lead to permanent brain damage. Multiple blows to the head can cause “punch-drunk” syndrome or dementia pugilistica, as evidenced by Muhammad Ali (born Cassius Clay, Jr. in 1942), whose parkinsonism was a result of his career in the boxing ring.

Falls, such as when playing, account for the greatest number of concussions in children aged 0–4 years. People over the age of 65 years also are at high risk of falling and sustaining a concussion. Individuals over age 75 have the greatest rate of hospitalization and death from concussions.


Symptoms of concussion include:

These symptoms might last from several minutes to several hours. More severe or longer-lasting symptoms can indicate a severe brain injury. The person with a concussion may or may not lose consciousness from the blow. More prolonged unconsciousness indicates a brain injury of greater severity.

The severity of concussion is graded on a three-point scale and is used as a basis for treatment decisions. The three grades are:

Days or weeks after the accident, the person might show symptoms of a condition called post-concussion syndrome. Signs of post-concussion syndrome include:


Concussions can occur while playing sports and other recreational pursuits. Consequently, all parents of children participating in such activities, along with coaches, athletes, and spectators, should be aware of the signs and symptoms of a concussion.


It is very important for those attending a person with concussion to pay close attention to the person's symptoms and progression immediately after the accident. The duration of unconsciousness and degree of confusion are important indicators of the severity of the injury and help guide the diagnostic process and treatment decisions.

A doctor, nurse, or emergency medical technician might make an immediate assessment based on the severity of the symptoms; a neurologic exam of the pupils, coordination, and sensation; and brief tests of orientation, memory, and concentration. Those with very mild concussions might not need to be hospitalized or have expensive diagnostic tests.

A loss of memory that may be caused by brain injury, such as concussion.
Dementia pugilistica—
Punch-drunk syndrome; Brain degeneration caused by multiple blows to the head, such as those sustained by boxers.
A neurological disorder that includes a fine tremor, muscular weakness and rigidity, and an altered way of walking.

Questionable or more severe cases can require computed tomography (CT) scans or magnetic resonance imaging (MRI) scans to look for brain injury. More extensive neuropsychologic testing may be done, especially on athletes who are at risk for repeat concussions.


The symptoms of concussion usually clear quickly and without lasting effect, if no further injury is sustained during the healing process. Rest is the most important part of treatment. Guidelines for returning to sports activities after a concussion follow five gradual steps. Athletes should rest first, then return to light activity, moving gradually to moderate and heavy activity with no contact. Once those stages pass, doctors can return them to practice and contact before clearing them for competition. The decision to return an athlete to competition is an individual one; there is no set time period following concussion when it is automatically safe to return to contact activities.


A person with a grade 3 concussion (involving any loss of consciousness, no matter how brief) should be examined by a medical professional either on the scene or in an emergency room. More severe symptoms may warrant a CT or MRI scan, along with a thorough neurological and physical exam. The person should be hospitalized if any abnormalities are found or if confusion persists. Prolonged unconsciousness and worsening symptoms require urgent neurosurgical evaluation or transfer to a trauma center. Following discharge from professional care, the patient is closely monitored for neurological symptoms, which may arise or worsen. If headaches or other symptoms worsen or last longer than one week in duration, a CT or MRI scan should be performed. Rest is important, as is avoidance of exertion or contact sports until a medical professional deems it is safe.

For someone who has sustained a concussion of any severity, it is imperative that he or she avoid the possibility of another blow to the head until well after all symptoms have cleared to prevent second-impact syndrome. A repeat concussion before full recovery can cause serious brain swelling and even death.


About 90% of concussions leave no lasting neurological problems. For the most part, concussions do not result in death. However, lasting problems caused by concussions can be serious. Symptoms of postconcussion syndrome can last for weeks or even months. The older the individual, the more likely the symptoms will last longer, especially if other medical conditions are also present.

Studies of concussion in contact sports have shown that the risk of sustaining a second concussion is even greater than it was for the first, if the person continues to engage in the sport. Athletes who have sustained concussions are more likely to have increased risk for physical and mental problems later in life.


Many cases of concussion can be prevented by using appropriate protective equipment. This includes seat belts and air bags in automobiles, and helmets in all contact sports. Helmets should also be worn when bicycling, skiing, skateboarding, or horseback riding. Soccer players should avoid heading the ball when it is kicked at high velocity from close range. Playground equipment should be underlaid with soft material such as sand or special matting.


The value of high-contact sports, such as boxing, football, or hockey, should be weighed against the high risk of brain injury during a young person's participation in the sport. Steering a child's general enthusiasm for sports into activities less apt to produce head impacts may reduce the likelihood of brain injury.

It is estimated that professional football players receive 900 to 1,500 blows to their heads each season they play. The National Football League (NFL) is conscious of the danger of players receiving concussions. In the 2010 NFL season, medical personnel began using standardized concussion assessment packages on the sidelines of each game to evaluate any player thought to have sustained a concussion while playing. The package includes a symptom checklist and a neurological examination, which includes a cognitive evaluation (e.g., “Are you thinking clearly?”) and a balance assessment (“Can you touch your nose with your forefingers on your left and right hands?”). The NFL estimates that the reason concussion numbers went up in 2015 was because more than double the number of players were screened for concussions as the league tries to minimize permanent effects of repeated concussions in its players.

Parents of children participating in high-impact sports should be aware of concussion policies for the organization sponsoring the sport, such as a school district. The policies should:

In addition, a health care professional should evaluate each concussion before any player is allowed to return to the game.

All athletes and parents (if the players are minors) should read, understand, and sign a concussion policy statement at the beginning of each season. These should not be signed if there is any problem or concern remaining, and children should not be allowed to participate under such conditions. Knowledge and active involvement in sports is a good way to prevent concussions from happening and, when they do occur, to minimize their severity.

See also Football .



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Dompier, T. P., et al. “Incidence of Concussion during Practice and Games in Youth, High School, and Collegiate American Football Players.” JAMA Pediatrics 169, no. 7 (July 2015): 659–65.


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American Academy of Neurology, 201 Chicago Ave., Minneapolis, MN, 55415, (612) 928-6000, Fax: (612) 454-2746, (800) 879-1960, .

Brain Injury Association of America, 1608 Spring Hill Rd., Suite 110, Vienna, VA, 22182, (703) 761-0750, Fax: (703) 761-0755, (800) 444-6443, braininjuryinfo@, .

Richard Robinson
Revised by Tish Davidson, AM
Revised by William Atkins, BB, BS, MBA
Revised by Teresa Odle, BA, ELS

  This information is not a tool for self-diagnosis or a substitute for professional care.