Chronic traumatic encephalopathy, better known as CTE, is back in the news after a former high school football player opened fire in a Manhattan office tower on Monday, killing four people.
Gunman Shane Tamura carried a three-page note in his wallet alleging that he had CTE, a serious brain disease that’s often linked with people who play contact sports, per The New York Times. The note also reportedly alleged that the NFL hid the potential danger of developing CTE from players. Tamura died by suicide after shooting himself in the chest, not the head—an act that is more common in people with CTE who die this way.
“Study my brain please,” the note said, per The Times. “I’m sorry.”
CTE has come and gone from the news over the years, often linked to a tragedy like this. But research into the devastating condition has been ongoing, along with efforts to prevent it. If it’s been a minute since you’ve read up on CTE, it’s understandable to have questions. Here’s the latest.
CTE is a devastating and deadly condition.
CTE is defined as a progressive neurodegenerative disease that causes brain damage similar to what’s seen in patients with Alzheimer’s disease, per the National Institutes of Health (NIH). There is a known link between repeated head trauma, contact sports, and the development of CTE.
CTE permanently destroys nerve cells in the brain and, over time, that damage can cause changes in behavior and mental abilities, according to the Centers for Disease Control and Prevention (CDC). There is a wide range of potential symptoms that someone with CTE can develop, but they include things like trouble with thinking and memory, suicidal thoughts, a change in mood and personality, difficulty with balance, and tremors, per the CDC.
“It is currently a diagnosis made only by examining the brain tissue of persons who have died,” says John Leddy, MD, medical director of the University at Buffalo Concussion Management Clinic. “It is not yet possible to diagnose CTE in living persons.”
There is ongoing research into CTE.
Research into how common CTE is and who will go on to develop it is ongoing, but there are some interesting—and admittedly scary—findings so far.
One of the more recent studies on CTE was published in JAMA Neurology in 2023. It analyzed 152 brains of people who had a history of repetitive head impacts from playing contact sports that were donated to a brain bank. The people whose brains were featured in the study were younger than age 30 when they died.
The researchers discovered that more than 40 percent of the donors had CTE based on established medical criteria. Nearly all of those cases were mild (considered to be stages 1 or 2 out of 4) and people who had CTE were usually older than those who didn’t have the disease. The most common cause of death in participants was suicide, followed by unintentional drug overdose. Most of the donors played sports at an amateur level and ¾ of those with CTE played football. The rest played ice hockey, soccer, wrestling, or rugby.
A 2024 study also published in JAMA Neurology tracked down former pro football players and asked them if they thought they had CTE. A whopping 34 percent said yes, citing a number of health problems and suicidal thoughts.
But this isn’t just a perceived health issue: A 2017 study published in JAMA analyzed the brains of 202 former football players who donated their brains to science, including 111 former NFL players. The researchers diagnosed a 110 out of 111 former pro football players—that’s 99 percent—with CTE.
The NFL has taken some steps to lower the risk of CTE.
The NFL has fielded growing criticism over the past few years over CTE risk, and players have openly spoken about it themselves. Former Philadelphia Eagles center Jason Kelce previously said on his New Heights podcast that he believes he has the condition due to constantly taking hits on the field. “I mean, I can virtually guarantee that I have CTE,” he said.
“There are no options available to persons with CTE since it cannot be diagnosed in living individuals,” Leddy says. But he points out that people who have concerning cognitive or emotional symptoms after years of playing contact sports shouldn’t assume they have CTE. Potentially treatable conditions like obesity, physical deconditioning, vascular disease (heart disease, stroke), diabetes, sleep apnea, depression and other psychiatric illnesses, and chronic pain, may cause similar symptoms, he says. “Persons who are experiencing physical or emotional distress, whether a former contact sport athlete or not, should not conclude that they have CTE,” Leddy says. “They should seek medical and psychological help to identify and treat any of these possible conditions.”
There has been growing pressure on the NFL in the past few years to try to lower the risk of head injuries, including concussions, which are also linked to CTE. According to NFL data, concussion rates have dropped over time. They leveled off during recent seasons, but the organization announced in February that the league had a “historic low” number of concussions during the 2024 season, including a 17 percent drop on concussions from the 2023 season.
The league allowed players to wear Guardian Caps, which are soft-shell covers for helmets that are designed to cushion the blow of impacts, during regular season games last year. But many players didn’t choose this option, and data to support the caps is weak. One pre-print study published in 2023 analyzed data from 42 NCAA Division I football players and concluded that there was no difference in several measurements of head impacts when players wore the caps. “This study suggests Guardian Caps are not effective in reducing the magnitude of head impacts experienced by NCAA Division I American football players,” the researchers wrote in the conclusion.
“Making sport safer by changing rules, improving equipment, and raising awareness to change behavior to reduce unnecessary repetitive head impacts is happening now,” Leddy says. “Recognizing the symptoms of concussion, removing the person from the activity right away, getting proper medical treatment, and not returning to the activity until a doctor has said you are ready, is another way to reduce the risk of possible long-term consequences from a brain injury.”
The NFL has not publicly commented on the shooting.
Korin Miller is a freelance writer specializing in general wellness, sexual health and relationships, and lifestyle trends, with work appearing in Men’s Health, Women’s Health, Self, Glamour, and more. She has a master’s degree from American University, lives by the beach, and hopes to own a teacup pig and taco truck one day.
