An epic clash in women’s soccer starts Thursday in Australia and New Zealand as 32 teams vie for the 2023 International Federation of Association Football (FIFA) Women’s World Cup, and the U.S. national team strives for an unprecedented three-peat. But also gaining attention are clashes of a different sort: high-speed hits to players’ heads. New research highlights the danger of concussions and potential long-term brain damage in an aggressive sport that already has many star players sitting out of the World Cup because of various types of bodily injuries. When it comes to concussions, the new studies point to some ways to improve players’ protection and health.

Briana Scurry knows about all this firsthand. As a soccer goalie, she never thought twice before blocking a ball. The two-time Olympic gold medalist and 1999 World Cup Champion routinely faced down dozens of players barreling straight at her, leapt toward soccer balls catapulted at 50 miles per hour and fearlessly plunged into a scramble of knees and feet to make a save. “You don’t even really care, at the time, about all these people. You just fly in there headfirst,” Scurry says. “It’s an acquired taste to be a goalkeeper.”

During a match in April 2010 for the Washington Freedom (a former Washington, D.C., team in the Women’s Professional Soccer league, which has been replaced with the National Women's Soccer League), she bent down to stop a low shot when a Philadelphia Independence forward slammed her knee into Scurry’s right temple. The forward tried to pull away at the last second to avoid Scurry, but they both bundled over. “My first thought is, ‘Did I make the save?’” Scurry recalls. She did. But when she stood up to kick the ball back into play, she immediately knew something was off. She felt woozy, and the names on her teammates’ jerseys started to blur. Most noticeably, she had an intense pain in her right temple and a throbbing behind her left ear. Scurry later found out that the blow resulted in a traumatic brain injury that smashed her occipital nerve.

“That was the last game I played,” Scurry says. “Before I knew it, it was season-ending because I wasn’t getting better—and then it was career-ending.”

This wasn’t the first head injury Scurry experienced on the field. She had three prior documented concussions—and she suspects she has had “maybe dozens” more that went undocumented or undetected over her decades-long soccer career. Research estimates suggest sports and recreation result in up to 3.8 million concussions in the U.S. each year and that about half of those go unreported. Head injuries are most common in high-contact sports, including hockey, boxing and lacrosse, and American football alone accounts for approximately 300,000 concussions a year. Even “softer” contact sports, such as water polo, volleyball, basketball and soccer, can place players at risk of head injuries and concussions. A 2019 study of U.S. high school athletes published in Pediatrics found that soccer had the highest concussion rate among girls’ teams and the fifth highest among boys’ teams.

“It’s important to remember all of the other types of sports that can cause concussion, and soccer is actually one of the highest-risk sports,” says Lissa Baird, a pediatric neurosurgeon at Boston Children’s Hospital and an associate professor at Harvard Medical School. “Sports carry huge benefits for people of all ages, especially kids, but the cumulative risk of concussions over time can have really profound impacts on somebody’s quality of life.”

An Invisible Injury

Though soccer isn’t normally considered a high-contact sport, the nature of the game can involve hard spills and hits from the ball, the ground and other players. People might not realize “how dangerous it actually is,” Scurry says. “As it’s gotten higher-competition, higher-stakes, you have more collisions,” she notes. “And those collisions are coming at a high rate of speed.”

The head’s sudden change in speed during an impact can cause a “kind of ricochet of the brain,” which floats in cerebrospinal fluid inside the skull, Baird explains. Such a ricochet actually stretches the brain’s neurons, which may disrupt the cells’ crucial connectivity and the flow of neurotransmitters. But signs of concussion are difficult to measure and detect, both on and off the field.

“It’s an invisible injury, so people tend to mask their symptoms,” says Teena Shetty, an associate attending neurologist at the Hospital for Special Surgery and associate professor of clinical neurology at Weill Cornell Medicine/New York-Presbyterian Hospital. “It’s not like a heart attack, where you can look at an EKG waveform and bloodwork, or an ACL injury where you can see it on an MRI.”

With concussions, neuroimaging scans typically show no signs of bleeding, bruising or other abnormalities in the brain. It usually triggers symptoms including headaches, fatigue, nausea, dizziness, blurry vision and cognitive dysfunction that could last a few days to months. Scurry says her April 2010 traumatic brain injury left her with a constellation of symptoms over the course of years. While Scurry “looked fine,” she had problems with light sensitivity, sleep, memory and balance, and a constant radiating pain behind her left ear, which eventually required surgery on her occipital nerve. The injury also took a significant toll on her mental health, she says, as she dealt with depression and anxiety. “Of all my years playing and training, my mental fitness was my greatest asset. I could focus on a ball with 90,000 people on the World Cup final looking at me in 107 degrees on the pitch,” she says. “A lot of people suffer in silence with regards to head injury and mental health.”

The severity and duration of concussion symptoms can vary immensely. Research has indicated that women present more severe symptoms and have longer recovery times, for example. And the variability is even more complex from person to person because every brain is “unique,” says Angela Lumba-Brown, a clinical associate professor of emergency medicine and pediatrics at Stanford University, who studies concussion subtypes. “We know that some people will present with the most common symptoms of headache and nausea, but then another person might mainly present with mood disruption and balance problems,” says Lumba-Brown, who sustained concussions herself while playing basketball in high school. "It really depends on the person and not necessarily where they got hit or even how they got hit.”

A player who recently sustained a concussion is more vulnerable to another concussion or injury, Lumba-Brown says. Repeatedly heading the ball has also raised alarm. In 2016 U.S. Club Soccer announced a no-heading rule for those younger than 11 and limited heading for players 13 and under; the U.K.’s Football Association is running a similar trial recommendation for those under 12. “A single header to the ball may not result in concussion immediately, but those cumulative impacts can definitely take their toll,” Baird says.

A Long Shadow

Multiple concussions—including repeated subconcussive impacts from heading the ball—have stirred discussion about the potential risk of future neurological conditions. A 2019 study published in the New England Journal of Medicine found that neurodegenerative disease was the primary cause of death in 1.7 percent of former male professional Scottish soccer players—approximately three times higher than in the general population. “That is a huge association,” says Peter Ueda, an assistant professor in clinical epidemiology at the Karolinska Institute in Sweden.

Ueda and his team wanted to see if similar trends could be seen in top-division Swedish soccer players. Their results, published in April in the Lancet, found soccer players had an approximately 1.5 times greater risk of Alzheimer’s disease and other dementias. “We don’t know whether this [data] is applicable to current elite players,” Ueda says. “Maybe they have a lower risk because they’re better equipped, and they have more professional [physical therapists]. Or maybe they are higher-risk because they start playing from a very early age, which they didn’t necessarily do back in the day.” He notes that trends are still emerging because many former professional players are just beginning to reach the age when these neurodegenerative diseases usually develop. Data are especially limited for women, who haven’t had the opportunity to play professionally for as long as men.

These long-term health implications have become “a big concern in the soccer community” and the public, Ueda says. On England’s 1966 World Cup team, four of the five players diagnosed with dementia recently died from it. In May three professional soccer players were diagnosed postmortem with chronic traumatic encephalopathy (CTE), a degenerative brain disease commonly studied among professional American football athletes and in other high-contact sports. CTE can present as dementia, mood swings and depression, but having any one of those conditions does not necessarily mean someone has CTE, Ueda says. The only way to diagnose the disease is through a postmortem autopsy, but even then, determining the exact causes is difficult.

“It’s not going to be possible to say CTE came from the five collisions and bad concussions you had in your career or the 10 years of heading the ball,” Lumba-Brown says. “But what the research does suggest, importantly, is that participation in professional soccer and elite soccer may result an increased risk for CTE as compared to general populations.”

A Path to Safer Play

For now Lumba-Brown and Scurry advise focusing on treating symptoms immediately and with appropriate care. Shetty says concussions require a multidisciplinary treatment, which may include physical and cognitive therapy. Longer-term care could require lifestyle modifications or even a change of sport. “I usually will tell my patients if they have more than two concussions playing a sport, they really should look for a different sport that’s a little bit safer for them,” Baird says.

Scurry says she had to “reboot” her brain through treatment. Today, at 51, “my brain is in a really good place,” she says. Now she spreads awareness about head injuries and concussions in soccer to help prevent them. Rigorous medical policies and protocols should be enforced by governing bodies and soccer leagues to promote change, she says. “We are still in the dark ages of asking the player if they’re okay when they’ve been knocked out,” Scurry adds. “It’s part of the culture of sports: shake it off and get on with it. A head injury, you don’t shake off.”

Professional soccer leagues and federations, including FIFA and the U.S. Major Soccer League, have official medical concussion protocols with preseason tests to establish neurocognitive baselines that give players a point of reference after an impact. They also conduct multiphase, on-site diagnoses and examinations. For the 2022 Men’s World Cup in Qatar, FIFA introduced an independent concussion assessment and rehabilitation service to assess any player who suffered a brain injury. This service included consultations with concussion experts to decide whether a player should remain in the game. Medical staff members and services, including injury spotters and replay video tablets to medically review collisions, were made available. FIFA also allowed one extra permanent substitute player per team for those who experienced actual or suspected concussions. According to a FIFA spokesperson, “A similar approach will be implemented for the FIFA Women’s World Cup 2023 as the wellbeing of all players involved remains FIFA’s priority.”

On the field, Baird says measures such as installing padding on goalposts can offer some simple protections. Players can also wear gear such as headbands and collars crafted to help dissipate an impact. Such devices are becoming more readily available, but Shetty says there’s still not enough evidence to medically support the safety and effectiveness of these early designs.

Scurry says more can still be done to protect player health and safety on and off the field. She continues to push for improved on-site third-party head injury evaluation after collisions, as well as training for coaches, staff and players to identify the signs and symptoms of a concussion. Importantly, Scurry hopes to shift the culture of injury in sports.

“I talk about this because I want to try to save that 18-year-old who has had a head injury, who’s trying to fight through it and doesn’t really understand why she doesn’t feel the way she used to,” Scurry says. “I want to get her understand that she’s okay, but she might need some help. It doesn’t mean you’re weak.”