Chronic traumatic encephalopathy (CTE) is a type of brain damage that has been found in 345 of 376 deceased formerNational Football League (NFL) players, according to a 2023 report by theBoston University CTE Center, which has led the effort to diagnose CTE cases. In comparison, a 2018 BU study of the general population found one CTE case in 164autopsies, and the one person with CTE had playedcollege football.^[1] The NFL acknowledged a link between playingAmerican football and being diagnosed with CTE in 2016, after denying such a link for over a decade and arguing that players' symptoms had other causes.^[2]

While much attention in the NFL has focused on limiting or treatingconcussions, the latest medical research indicates that the brain damage in CTE is caused by the cumulative impact of all collisions involving a player's head,^[3][4] which confirms what was generally known nearly a century ago but was then largely forgotten.^[5] The NFL has implemented rule changes to reduce collisions to the head^[6] and has sought to improvefootball helmet design.^[7] Critics respond that significant head trauma is inevitable for bigger, faster players in tackle football^[8] and that helmets are of limited use in preventing a player's brain from crashing into their skull, which is the cause of the brain damage that leads to CTE.^[9]

As more parents (including some NFL players) decide not to let their children play football,^[10][11] it remains to be seen whether football will eventually face a significant decline in popularity^[12] likeboxing, which fell from prominence as the brain damage suffered by ex-boxers drew more public attention.^[13] As of 2023^[update] football is the most-watched sport in the U.S. by a substantial margin whilebasketball is the most-played sport.^[14]

Although the symptoms of CTE can vary, it doesn't directly cause death but instead changes personality and behavior, making a person not feel like themselves anymore.^[15] Players with CTE can become isolated from their friends.^[16] Sometimes they become unable to tell a story,^[17] carry on a conversation,^[18] or recognize their loved ones.^[19] One former player later found to have CTE described having headaches that felt like ice picks hitting his brain.^[20]

Some former players with CTE suffer from memory loss and depression.^[21] Some players and those around them deal with their violent mood swings, rage,^[22] and paranoia.^[23][24] In some cases, damage to players' brains contributes to severe alcoholism leading to death.^[25][26] Two formerNFL Man of the Year winners suffering from CTE symptoms have committed suicide by shooting themselves in the chest, with the intent of leaving their brains intact to be studied for the damage inflicted by football.^[27][28]

Heisman Trophy winner and former NFL All-ProBo Jackson said in a 2017 interview withUSA Today that if he had known about the risks associated with CTE, he would never have played football, and he discourages his children from doing so.^[29] In late 2017, former running backLarry Johnson, who holds the NFL record for most rushing attempts in a season, reported having symptoms akin toAaron Hernandez, including memory blanks, suicidal thoughts and thoughts of committing violent acts. Although there is no way to positively diagnose CTE before death, Johnson believes he is living with the disease.^[30]

The CEO of the Concussion Legacy Foundation states that "[l]ater stage CTE (stage 3 and 4) is associated with dementia, but early-stage CTE (stage 1 and 2) is more associated with what is called neurobehavioral dysregulation, which includes violent, impulsive, or explosive behavior, inappropriate behavior, aggression, rage, 'short fuse,' and lack of behavioral control."^[31]

Each year of playing tackle football increases a player's risk of developing CTE by 30 percent.^[32] Family members and friends frequently struggle to try and provide care for former players with CTE,^[33][34] while the NFL has been criticized for not following through on its limited promises^[35] and not using basic tests to identify dementia in former players for its legal settlement.^[36]

A common definitive test currently can be made only by examining the brain tissue of a deceased victim. 345 of 376 NFL players whose brains have been autopsied had CTE.^[1]

As the vast majority of deceased former players never have specialized autopsies done on their brains -- the first such autopsy was not performed until 2002,^[37] and the families of most deceased players keep their autopsy results private -- the following list shows a small fraction of NFL players who have had CTE. The age listed to the right of many players' names is when their CTE symptoms began, as indicated in the referenced sources, although in some cases symptoms could have begun earlier.

Included in the list are players diagnosed withamyotrophic lateral sclerosis (ALS) who were never testedpost-mortem for CTE but whose history appears consistent with CTE. A typical diagnosis of ALS has primarily been based on the symptoms and signs the physician observes in the patient and a series of tests to rule out other diseases^[161] and therefore, prior to the discovery of CTE as a phenomenon in ex-American football players, many CTE cases were diagnosed as ALS. After CTE was first diagnosed in 2002 in the brain tissue ofMike Webster,^[162] brain donation for specialized autopsies to check for CTE have become more available.^[163]

Acohort mortality study run by theNational Institute for Occupational Safety and Health (NIOSH) examined 3,349 NFL players who played at least five full seasons from 1959 to 1988.^[164][165] Findings showed that while NFL players lived longer than the average American male — although that could be due to the correlation between income and life expectancy in the U.S.^[166] — the risk of death associated withneurodegenerative disorders was about three times higher among the NFL cohort.^[164][165] The risk for death fromAlzheimer's disease andALS were about four times higher among the NFL cohort.^[164]

These players have publicly acknowledged either having been diagnosed with likely CTE or having experienced symptoms, such as dementia or unusual memory loss, consistent with CTE but that could have other causes or CTE could be one of a combination of causes. For example, ex-players that have presented with symptoms late in life may have other forms of age-related dementia. In some cases, the player has received a diagnosis of ALS, but their symptoms are consistent with CTE.

Around 4,500 players broughtmultiple lawsuits against the NFL alleging that it had covered up a growing body of medical evidence about the preponderance of head-trauma related CTE in ex-NFL players, and some testimonials have come in that context.

At present, there is no definitive CTE test available for living persons. The age listed to the right of many players' names is when their symptoms that possibly indicate CTE began, as provided in the referenced sources, although in some cases symptoms could have begun earlier.

After multiple lawsuits^[235] and many years of litigation, the NFL and lawyers for around 4,500 former players (or their estates) announced a financial settlement of $765 million in 2013.^[258] The list below currently contains fewer than half of those players.

The NFL was heavily criticized when it became known that race norming, which assumed that black players started with lower cognitive levels than white players, was being used in determining whether players qualified for help in the initial years of the settlement. The parties to the settlement discontinued the use of race norming in June 2021.^{[259][260][261]}

More recently, many players and their families have complained of being unfairly denied benefits under the settlement.^[262] Although the settlement's terms require that the latest medical tests be used to diagnose mental impairment, basic imaging tests are not paid for, saving "the NFL tens of millions in medical costs alone". As one neuroradiologist said, “If you're trying to find dementia in the last 10 or 15 years and you're not using imaging, you're not really trying that hard.”^[263]