Chronic traumatic encephalopathy (CTE) has been found in 345 of 376 deceased former National Football League (NFL) players' brains, according to a 2023 report by the Boston 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 164 autopsies, and that one person with CTE had played college football.^[1] The NFL acknowledged a link between playing American 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 treating concussions, the latest medical research indicates that the brain damage in CTE is from 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 improve 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] like boxing, which fell from prominence as the brain damage suffered by ex-boxers drew more public attention.^[13] Football is currently the most-watched sport in the U.S. by a substantial margin while basketball is the most-played sport.^[14]

How players are affected

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 former NFL Man of the Year winners suffering from CTE symptoms shot themselves in the chest so their brains could be studied for the damage inflicted by football.^[27][28]

Heisman Trophy winner and former NFL All-Pro Bo Jackson said in a 2017 interview with USA 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 Kansas City Chiefs running back Larry Johnson reported having symptoms akin to Aaron 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]

Each year of playing tackle football increases a player's risk of developing CTE by 30 percent.^[31] Family members and friends frequently struggle to try and provide care for former players with CTE.^[32][33][34]

Former players with CTE confirmed post-mortem

A common definitive test currently can be made only by examining the brain tissue of a deceased victim. The latest research indicates that 345 of 376 NFL players whose brains were autopsied had CTE.^[1] As the vast majority of deceased former players never have specialized autopsies done on their brains, the first such autopsy wasn't performed until 2002,^[35] and the families of many 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.

Deceased players suspected of having had CTE

Included in the list are players diagnosed with amyotrophic lateral sclerosis (ALS) who were never tested post-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^[135] 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 of Mike Webster,^[136] brain donation for specialized autopsies to check for CTE have become more available.^[137]

A cohort mortality study run by the National Institute for Occupational Safety and Health (NIOSH) examined 3,349 NFL players who played at least five full seasons from 1959 to 1988.^[138][139] Findings showed that while NFL players lived longer than the average American male — although that was probably due to the correlation between income and life expectancy in the U.S.^[140] — the risk of death associated with neurodegenerative disorders was about three times higher among the NFL cohort.^[138][139] The risk for death from Alzheimer's disease and ALS were about four times higher among the NFL cohort.^[138] Some on this list may have had dementia not related to ALS or CTE.

Living former players diagnosed with CTE or ALS or reporting symptoms consistent with CTE or ALS

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. In some cases, the player has received a diagnosis of ALS, but their symptoms are consistent with CTE. There are also around 4,500 former players who joined a class action lawsuit 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.^[174]

Some of these ex-players may have medical conditions other than CTE or ALS. For example, ex-players that have presented with symptoms late in life may have other forms of age-related dementia. Some of the former players on this list came forward only in the context of the class action lawsuit versus the NFL. At present, there is no definitive CTE test available for living persons. Their average age is 51.

Former players listed as plaintiffs in lawsuits against the NFL for concussion-related injuries received after playing

This list is incomplete. The NFL reportedly reached a settlement in 2013 with around 4,500 former players (or their estates). This list currently contains fewer than half that number.