CTE was first noticed in boxers who suffered blows to the head over many years. More recently, football players have become the focus of study.
In recent years, concerns about CTE have led high school and college programs to restrict hits to the head, and the NFL prohibits helmet-to-helmet hits.
About 4,000 former NFL players filed a class-action lawsuit last year claiming the league failed to protect players from traumatic brain injuries or warn them about the dangers of concussions. The NFL has said that it never intentionally hid the dangers of concussion from players, and that it is now doing what it can to protect players against concussions. The league has given a $30 million research grant to the U.S. National Institutes of Health for that purpose.
Last December, Boston University School of Medicine researchers reported in the journal Brain that people with CTE experience four specific phases, beginning with memory disruption and thinking problems and ending with aggression.
The Boston researchers said the condition had been diagnosed in 34 former professional players and nine former college football players.
The Boston University Center for the Study of Traumatic Encephalopathy has more about chronic traumatic encephalopathy.
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