Causes and Risk Factors of Concussions

Causes of Sports and Non-Sports Concussions

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Describing the cause of a concussion is not an exact science—at least not yet. There is plenty we don't know about what happens to cause a concussion, a term not even universally used. A "concussion" is the word of choice in sports, but "mild traumatic brain injury" is the term used in military settings. Even the research is different between the two.

Either way, the only constant in the cause of concussions is that there is a blow to the head.

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Common Causes

Damage to the brain from direct contact, twisting (also known as "shearing"), and striking the inside of the skull during acceleration or deceleration (known as coup-contracoup) is the actual cause of concussion. Certain types of activities are known to have a higher incidence of this.

Concussion causes can be divided into two categories: sports-related concussions and non-sports concussions. Between the two, there is little difference in the actual damage to the brain, but focused medical care and concussion detection in sports does change the reporting—and therefore the incidence rates—on and off the field.

Sports-Related Causes

Of all sports, boxing is the king of concussions. Indeed, the only guaranteed way to win a bout is to cause a concussion in your opponent (knock him out).

Research on amateur boxers shows that a knockout isn't the only way to cause a concussion though. Repetitive blows to the head—even though they don't result in an acute loss of consciousness—may cause concussions. It takes nearly as long for a boxer to fully recover after a bout, whether he is knocked out or not. In fact, if a boxer is not knocked out, it just means he spent more time getting pummeled.

Football has by far the largest incidence of concussions in youth sports. It also has the largest overall participation in a single sport. High school athletes have statistically significant increases in long-term concussion severity over college athletes. Researchers aren't sure why, especially since college players get more intense injuries on the field.

Knowing that football causes concussions has led to much more medical support for players on the field and in the doctor's office. All the attention might have increased the detection and reporting of concussions, which in turn adds to the statistics. College athletes have more access to medical care both on and off the field, which might have something to do with how college athletes recover faster.

Women's soccer is the female team sport with the highest rate of concussion. Unlike men's soccer—where head to head contact between players is the most likely cause of concussion—women's soccer causes more concussions when players hit the ground.

But virtually every scholastic team sport causes concussions in some way. Volleyball, cheerleading, softball, baseball, basketball, and lacrosse are all responsible for concussions to players in increasing numbers since the late 20th century.

In scholastic competition, wrestling is the individual (non-team) sport with the highest rate of concussions. Takedowns cause the most concussions.

Non-Sports Concussion Causes

Outside of the gridiron or the ring, the most common causes of concussion happen on the battlefield. Military or combat-related concussions aren't reported quite the same way as sports-related concussions are, so there is no way to do a direct comparison. However, the concussion causes in combat are well documented and tend to be most often related to explosions.

As in sports-related concussions, combatants have access to medical personnel before and after ​a concussion, which allows for more in-depth assessments as well as pre-concussion baseline assessments. Those assessments help with concussion detection after an injury.

Other than explosions, other concussion causes in military duty are similar to occupational injuries in non-military industries: vehicle collisions, falls, accidental head strikes, etc. Outside of military duty, most people don't get regular neurological examinations to determine baseline neurological function pre-injury. That makes it much harder to correctly identify concussions off the playing field or the battlefield.


Concussion was long thought to be a relatively minor medical condition—or not a condition at all. Only since the turn of the 21st Century has the seriousness of concussion really come to light and research is still catching up.

There is no clear genetic marker to identify higher risk of injury or poor outcome, but women did seem to have a lower threshold for concussion injury than men in both sports and military data.

Risk Factors

The biggest risk factor for concussion is a previous concussion or repetitive blows to the head. Boxing, for example, is associated with much higher risk of long-term concussive damage due to direct head strikes. Avoiding direct, repetitive injury is the single most important factor in lowering personal risk for a concussion.

That being said, sometimes it isn't possible to completely avoid the behavior. A football player or career soldier is going to be exposed to potential injury. One study identified that there are potentially ways to mitigate the damage potential incurred during a blow to the head. For example, increasing neck muscle strength showed a statistically significant reduction in damage, especially when coupled with anticipating and bracing for impact. When possible, wearing well-constructed safety helmets also reduces risk, as well as replacing helmets when needed.

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