In the past three decades, soccer has gained popularity with high school athletes as the sport of choice for both girls and boys.

Nearly 800,000 high school students of both sexes played on school soccer teams last year, up from roughly 50,000 in 1969.

As interest in youth soccer has grown, so has the number of concussions in young players. A new study published in JAMA Pediatrics looked at the number and cause of concussions among soccer players. Researchers sampled 100 high schools across the United States between 2005 and 2014 to draw their conclusions.

Based on their examination, the researchers from the University of Colorado’s School of Public Health found that, contrary to conventional wisdom, most concussions were not a result of heading the ball – the practice of hitting the ball off one’s head.

Only about one-third of boys’ concussions and one quarter of girls’ concussions resulted from heading a ball. The majority of concussions among high school soccer players were due to aggressive play. Sixty-nine percent of boys and 51 percent of girls who suffered a concussion were hurt by crashing into an opponent while playing defense, goal tending, receiving a pass or dribbling a ball down a field.

Dr. Eric Warren , a sports medicine specialist at Novant Health Waxhaw Family and Sports Medicine in Waxhaw, North Carolina, said the results of the study surprised him. In his experience, headers caused more concussions than direct contact. But the sport is indeed responsible for a range of injuries, he said.

“The most common soccer injuries I see in my practice are concussions, knee and ankle injuries,” Warren said.

In 2012, there were 163,670 young athletes treated for concussion in an emergency room, according to statistics from the Youth Sports Safety Alliance. And even as the number of student athletes participating in soccer, basketball and football dropped between 1997 and 2007, the rate of concussions in those sports more than doubled.

The alliance reports that girls are more likely to report concussions than boys when competing in sports commonly played by both. Girls age 10 to 19 are most susceptible to traumatic brain injury when playing soccer, basketball or bicycling.

“We’ve known that soccer is a high-risk sport for both men and women, and there is more risk for women,” Warren said. “A concussion is not a football-only injury. We need to make soccer safer, but eliminating heading for younger athletes may not be the only answer.”

Soccer has been widely regarded as a safer sport than football or baseball, but rising head injuries are calling these assumptions into question. The nonprofit Sports Legacy Institute has launched a campaign called “Safer Soccer” that aims by 2017 to eliminate the practice of heading.

Warren thinks heading should be limited in youth soccer to children older than 14 years of age, because younger players are still developing, which makes them at higher risk for concussions.

The JAMA study researchers concluded that though banning heading in youth soccer would prevent some concussions, reducing athlete on athlete contact would be a more effective way of preventing head and other injuries.

“We have become a more sports-oriented culture over the years,” Warren said. “Our young athletes are bigger, faster and stronger than they’ve ever been, so when there is an impact, more force is generated with every contact compared to 20 or 30 years ago.”

The Centers for Disease Control and Prevention defines a concussion as a type of traumatic brain injury caused by a blow, a bump or jolt to the head or a hit taken to the body that causes the head to move rapidly back and forth.

Concussions aren’t always readily apparent, warns the agency, because symptoms may not be evident immediately.

Student athletes that may have a concussion might complain of the following symptoms:

  • Headache or pressure to the head.
  • Nausea.
  • Dizziness.
  • Feeling foggy.
  • Blurry vision.
  • Sensitivity to light or noise.
  • Confusion.

Parents should monitor children for changes in mood or behavior, forgetfulness and clumsiness. Some symptoms may worsen over time. Take a child to the emergency room immediately if notice these danger signs:

  • One pupil that is larger than the other.
  • Drowsiness.
  • Lack of coordination.
  • Convulsions.
  • Slurred speech.
  • Repeated vomiting.
  • Confusion or agitation.
  • Loss of consciousness, even briefly.

“Parents and coaches should look for changes in the child,” Warren added. “If he or she looks dazed or confused, has problems with balance or complains of headaches or dizziness, the child should receive medical attention.”

How to prevent concussions and other brain injuries

Warren said he believes that having referees better enforce the rules on body contact and contact in the air would reduce the risk of concussion.

If your child has had a concussion, the CDC says to let the injury heal and keep the child from playing the game. Young athletes who engage in sports too soon risk a second concussion, which increases the risk of more permanent brain damage.

“Coaches and parents should follow the adage: when in doubt, hold them out,” Warren said. Putting a child back in the game before he or she has properly healed can cause second impact syndrome, a condition where a second concussion causes rapid and severe brain swelling.

The risk of reinjury is so high that Warren recommended children undergo balance testing, an eye exam to track vision and a cognitive test on a computer or in school to determine whether the child has healed from the concussion before putting him or her back in the game.

Coaches should be alerted to the fact that a child had suffered a concussion, whether it occurs during soccer or another sport.

Soccer players should be encouraged to follow their coach’s rules for safety, and parents are urged to remind children of good sportsmanship.