In the new movie Concussion, Will Smith plays a neuropathologist who performed a game-changing autopsy on former Pittsburgh Steelers center Mike Webster in 2002. After a career in which Webster earned four Super Bowl rings and a spot in the Pro Football Hall of Fame, he suffered from memory loss, depression, and dementia, was homeless at times, and died at age 50. (The movie is based on a GQ article that describes Webster’s psychiatric symptoms, including “pissing in his oven and squirting Super Glue on his rotting teeth.”) When the neuropathologist, Bennet Omalu, analyzed Webster’s brain tissue, he discovered clumps of tau proteins, generally associated with neuro­degeneration. In 2005, he published a paper arguing that Webster had suffered from what he recognized as chronic traumatic encephalopathy, or CTE, brought on by more than two decades of brain battering on the field.

As Omalu and others studied the brains of dozens of former players who had died, they continued to discover signs of CTE. Not surprisingly, the National Football League fought to discredit the work, possibly hoping to avoid expensive disability payments to ex-players. “You’re going to war with a corporation that owns a day of the week,” an associate warns Omalu in Concussion. Yet despite the NFL’s obstructionism, the connection between repetitive head injury and neurodegenerative disease has only grown stronger with time. While many athletes who suffer concussions do not go on to develop CTE, every time it crops up in an autopsy it’s in someone who “had a history of repetitive hits to the head,” says Robert Stern, director of the clinical core of the Alzheimer’s Disease Center at the Boston University School of Medicine.

The issue now extends far beyond the NFL to children who play football, soccer, hockey, and other sports, especially because new research is revealing the pervasiveness of head injury in young athletes. Neuroscientists are finding that concussion can affect brain function in subtle ways, and that kids may have a special vulnerability. It’s possible that better helmets and other equipment could play some role in reducing the risk, but they are unlikely to solve the problem. It’s time to change the rules of the games.

Long-term consequences

In 2013, a report from the Institute of Medicine called for greater attention to concussions across the age spectrum, but especially in younger kids. In response, epidemiologists from the Datalys Center for Sports Injury Research and Prevention in Indiana analyzed information collected by athletic trainers in 2012 and 2013. They found that roughly one in 20 college football players sustained at least one concussion in the course of a season. Among high school students, that number was one in 14. And among youth players, it was one in 30, though lead researcher Tom ­Dompier told me he suspects that last number is an underestimate. Concussion occurs when the brain slams against the inside of the skull, but 90 percent of the time it does not cause loss of consciousness or other very obvious effects. So especially among five- to seven-year-olds, it’s possible that they “just didn’t know how to articulate” their symptoms, Dompier says.

Other researchers are trying to better identify concussion symptoms that can show up long after a game. These can include behavioral changes like temper tantrums and irritability, according to Kristy ­Arbogast, co–scientific director of the Center for Injury Research Prevention at the Children’s Hospital of Philadelphia. In some children, concussion can cause subtle disruptions to ocular motor coördination that were not routinely evaluated in the past. These can lead to headaches, dizziness, and nausea when kids return to school and try to focus on the blackboard. “We’re finally getting some clarity on what concussion looks like at different ages and in different children,” she says. That, she adds, will allow physicians to diagnose and treat more cases.

At the same time, scientists are pinpointing how head injury affects young brains. To date, no one has performed a critical experiment in which children who play contact sports are followed for decades. But several lines of evidence suggest that concussions and even lesser head trauma can have long-term consequences for them, challenging the conventional wisdom that the young brain’s plasticity makes it more resilient. “Plasticity doesn’t seem to work that way,” says Stern. Instead, he argues that during certain windows of development, children’s brains may actually be more vulnerable to lasting damage than adults’.

Stern and his colleagues have categorized a group of retired NFL players according to whether they began playing before or after the age of 12. Controlling for the total number of years in football, the researchers found that those who started earlier fared worse on tests of cognitive flexibility and executive function. An advanced version of magnetic resonance imaging also showed that these players had more disruptions to a bundle of nerve fibers, or axons, called the corpus callosum. Between the ages of eight and 12, the brain undergoes a period of intense axonal growth and myelination (in which an insulating layer accumulates around the nerve cells), facilitating communication. Stern speculates that the players who started earlier may have sustained axonal injuries that prevented their brains from developing fully during this critical window, leading to long-term impairment.

Last year, researchers at Purdue University compared the neurocognitive function of high school football players before and after a single season. Strikingly, even athletes who had not suffered a diagnosable concussion performed worse on tests of visual memory after months of football. The study was small, and it’s unclear whether its findings can be generalized. But it’s reasonable to be concerned about brain changes brought on by head impact, however subtle. “We do everything to make sure our kids have the best possible chance at success in life,” says Stern. “And yet we drop them off at a field and say, ‘Go hit your head over and over again.’ It’s incongruous.”

That’s why sports leagues must do much more to reduce the frequency and intensity of head impacts. In soccer, young children simply should not be heading the ball. Last year, a group of parents filed a class action suit against FIFA, U.S. Soccer, and the American Youth Soccer Organization to force restrictions on this practice. In November, the suit was settled with the U.S. Soccer Federation, which announced a ban on heading for children 10 and younger and limitations on heading during practice for kids between the ages of 11 and 13. (For technical reasons, the suit against FIFA was not allowed to proceed.) This is actually just a small step; if it’s true that children experience a critical window of brain development before the age of 12, they should not be expected to head the ball at age 11. In other sports, too, more could be done: in baseball, leagues could outlaw head-first slides into bases. The leaders of USA Hockey have already forbidden body-checking, in which a player is slammed into the wall around the ice, for kids under 13. But that will have limited effect unless the rules are strictly enforced.

Much of the head hitting in football occurs during practices, as research by Dompier and others shows. That can be minimized through coach education and prudent changes. For instance, old-time coaches often assigned young players to activities like the Oklahoma drill, in which players line up a few feet apart and run at each other. “Once you outlaw silly drills like that and limit how many hours the kids can do full contact, you can actually make practices pretty safe,” he says. In 2012, the Pop Warner youth football organization instituted new restrictions on blocking and tackling drills. But even contact-free practices leave kids vulnerable to concussions in games, which is why bigger changes should follow. Youth leagues should switch to flag football and ban tackling for kids under 14. And high school leagues should end kickoff and punt returns, in which players charge full speed at each other from opposite directions. (Even the NFL has changed the yard line for kickoffs to reduce the number of returns.)

Further research is still required to understand how common concussions really are in kids and how their brain structure and cognitive function may be affected years after playing contact sports. Leagues might mandate helmet sensors to detect the frequency and force of hits, though the severity of impacts that cause concussions can vary from person to person. What ultimately needs to be developed is a quick blood test, such as a screen for the proteins that appear in elevated amounts after a brain injury.

In the meantime, as the NFL’s history shows, we shouldn’t ignore potentially devastating evidence or assume we know how serious repeated head contact is. It’s true that we can’t easily generalize from adults to kids. But if ever there were cause for extreme caution, children’s brains are it.