Is football too dangerous for kids’ brains? These scientists are racing to find out

Chris Nowinski lived the athlete’s dream: playing high school football, then National Collegiate Athletic Association Division I football at Harvard University and then professional wrestling in the WWE.

But at just age 24, after more than a decade of contact sports, Nowinski developed a grueling “three-year headache” and REM (rapid eye movement) sleep behavior disorder—a condition in which people act out their dreams, sometimes dangerously. “I had to be sedated every night so I wouldn’t go chasing shadows, jumping off beds or putting people in headlocks,” recalls Nowinski, now 47.

Nowinski’s experience is extreme. But cognitive dysfunction, mood issues and brain damage can be the cost of repetitive blows to the head— a phenomenon first observed as “punch drunk” syndrome in boxers in 1928. Scientists now call this condition chronic traumatic encephalopathy, or CTE. It is a degenerative brain disease associated with dementia and early death. It’s rare, affecting less than 1 percent of the population; but among athletes playing contact sports, it is alarmingly common.

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Nowinski retired from the WWE after a particularly severe concussion. Desperate to fix his pain, he decided to study head trauma, becoming a behavioral neuroscientist at Boston University and directing the Concussion Legacy Foundation.

Data he and his colleagues published last month in the BMJ suggests at least one in four former National Football League (NFL) players who died between 2016 and 2021 had CTE—Nowinski says this is an underestimate. Other analyses suggest about 40 percent of amateur athletes playing contact sports show brain changes that are characteristic of CTE, too.

“CTE is affecting far more people than anyone wants to accept,” Nowinski says. He puts his own odds of having it at 50–50.

Millions of amateur athletes play tackle football each year, and as evidence mounts at the professional level of the dangers of CTE, parents are increasingly worried about their children going into the sport. Some are banning their kids from taking up football; others defend it for building bonds and teaching life skills. Is high school football the new smoking, or are the health concerns overblown?

There isn’t strong evidence that playing at an early age is bad for you, but players need to be “developmentally ready,” says Jeffrey Strelzik, an assistant professor of child neurology at Children’s National Hospital in Washington, D.C. “Why would we have a small, wobbly five-year-old with poor neck strength tackle?”

“Any risk needs to be weighed against the benefits of playing team sports,” he adds.

Getting My “Bell Rung”

Garrit, a 33-year-old former college linebacker, who asked to be identified by his first name for privacy reasons, started playing tackle football at 10. He remembers getting his “bell rung” over the years. “You’d hit someone, and your vision would go fuzzy, and you’d hear this high-pitch noise,” he recalls. Later in his career, he slammed his head on the ground and couldn’t remember the plays for the rest of the game.

“It was on you to self-report, and there was incentive not to because you didn’t want to miss playing time,” Garrit says. “I knew if I said something, that was probably the end of my career.”

Players often downplay symptoms to stay on the field—and many signs of brain trauma, such as headaches, memory problems and fatigue, are easy to hide. CTE appears driven not by concussions but by countless small impacts that jostle the brain: say, a header in soccer or a punch in boxing.

For every diagnosed concussion, college football players sustain about340 hits harder than the median concussive impact. And in a single season, a high school or college football player absorbs an estimated 600 to 1,000 subconcussive blows.

These micro injuries don’t always announce themselves: the brain has no pain receptors, says Michael Buckland, a neuropathologist at the University of Sydney, who founded the Australian Sports Brain Bank. “If you twist your ankle, it bloody hurts. You don’t get that feedback from the brain,” he says. The exception is when the damage compromises basic functioning so much that you lose consciousness or have a seizure.

It’s the cumulative g-force to the head over years that puts people at highest risk, says Daniel Daneshvar, a neuroscientist and chair of physical medicine and rehabilitation at Mass General Brigham and Harvard University. Daneshvar co-authored the study that found that one in four NFL players had CTE with Nowinski and others, and he also played football through college.

“I learned a lot from football, and I want people to continue playing, but I want them to do it in a way that’s safer for their brains,” he says.

“They Became a Different Person”

CTE is characterized by misfolded proteins in the brain called phosphorylated tau (p-tau), a type that is also implicated in Alzheimer’s. It’s been seen in people who play contact sports, such as hockey, rugby or wrestling, experience military combat or experience domestic violence.

The brain’s surface has ridges and valleys, and CTE tangles are found in the depths of those valleys, called the cortical sulci, and surround blood vessels. They are the physical manifestation of diseased or dying brain cells, Daneshvar adds, and tend to worsen over time.

Like a zombie apocalypse, Buckland says, these toxic protein tangles can induce other proteins they touch to misfold, spreading through the brain. It is highly unlikely to see any p-tau tangles in a normal brain under age 50, so seeing CTE in the brains of athletes in their 20s and 30s is “striking and alarming,” he says.

CTE can only be definitively diagnosed after death. But signs can show up earlier: short-term memory loss, emotional problems, trouble with executive function. Personality change is the number one sign reported by families, Nowinski says. “You often hear: ‘They became a different person.’”

The condition is also linked to sudden shifts in mood or “flying off the handle,” Daneshvar says, plus depression, dementia, anxiety and parkinsonism—problems that can sometimes surface years after athletes retire. Families can endure years of “going through hell” without an answer, Buckland says: marriages broken apart, children estranged, people on suicide watch.

Still, the effects are “variable,” Buckland says, and researchers are racing to understand the clinical symptoms of CTE. Many of the condition’s early signs, such as depression or impulsivity, can stem from other factors, and some experts worry about making premature diagnoses.

There is no cure for CTE, but the symptoms can be treated. “If we make the brain more resilient, people will be able to function at a high level for longer,” Daneshvar says. “People can get better.”

Mixed Signals

Importantly, CTE data show correlation, not causation, to playing football. Across multiple experiments on donated brains, between 5 and 72 percent of people with repetitive head impacts from contact sports had CTE at death. For former NFL players, the range has been between 9.6 and 99 percent. Scientists see a troubling trend but are still investigating how the disease develops.

Some studies suggest a dose-response relationship: the more head hits one receives, the higher the risk of cognitive and behavioral problems in later life. One 2019 analysis found that each year of tackle football appeared to raise the odds of CTE by an estimated 30 percent. Other studies have seen minimal effects: a 2021 longitudinal study found that middle-aged men who played high school football reported no worse brain health than men who played other sports or none at all.

“It’s possible that we’ll find out that there is a close causative link that shows the risks [of football] outweigh the benefits,” Strelzik says. But the science “isn’t there yet.”

And kids are not just “little adults,” he adds, noting CTE research may be skewed by its reliance on donated adult brains. “We don’t have enough data to suggest playing at an early age is bad for you. It may or may not be.”

The NFL has introduced stricter concussion protocols, penalties for high-risk tackles, as well as better gear and cutting full-contact practice to once a week. “The NFL continuously strives to make the game of football safer … to reduce concussions and head impacts,” an NFL spokesperson told Scientific American. They also noted an expanding set of resources to support athletes’ well-being even after players retire.

Experts say this isn’t enough. Even the best helmets and other gear can give a false sense of security, Nowinski says, because they’re primarily designed to reduce skull fracture and linear acceleration, not the rotational acceleration that leads to CTE.

Sports organizations invest hundreds of millions of dollars in recruiting children, Buckland says. “If they’re going to sell their product to children, they have a responsibility to ensure that everything is being done to protect them.” They have also been slow to respond to the emerging evidence, he adds. “I do worry that players, even today, aren’t being appropriately informed of the risk.”

Much of the damage may be done before players reach the big leagues. One study found that around 70 percent of head hits occur in practice. If youth teams practiced like the pros, confining full contact to once a week, impacts could fall by more than half, Daneshvar says.

Buckland and Nowinski say there should be no full contact before high school, or age 14—better still, Buckland says, pick a sport that doesn’t involve getting hit in the head. If you still have a burning desire to play tackle football, minimize your hits, Strelzik adds.

Whether the evidence spells the end of peewee football remains up in the air. “There will be a reckoning at some point, but I don’t know whether that will stop people from playing,” says Dylan Jeffay, 33, who played from seventh grade through college. “It’s built into the culture.”

For Garrit, knowing the data wouldn’t have changed a thing. “Especially for younger me, there’s no way it changes what I wanted to do,” he says. “I would probably just think, ‘That’s soft.’”

“I don’t think my life would have been as rich as it has been without the sport,” he says.

Nowinski is torn about his own child lacing up. “I’ve heard so many stories of great people having terrible experiences and giving terrible experiences to their families that I can’t imagine a scenario in which I’ll feel justified in exposing my child to this disease,” he says.

“We say that sport teaches character, leadership and resilience,” Nowinski says. “It’s time to prove it by stepping up and taking care of our teammates.”