​Boston University’s Center for the Study of Traumatic Encephalopathy (CTE Center) has diagnosed the late Marshawn Kneeland, a former Dallas Cowboys defensive end, with chronic traumatic encephalopathy. Kneeland, who died by suicide in November 2025 at age 24, was found to have Stage 1 CTE, according to the center.
Dr. Ann McKee, director of the BU CTE Center and chief of neuropathology for the VA Boston Healthcare System, stated in a prepared release, “Unfortunately, I was not surprised to find CTE in Mr. Kneeland’s brain, because we have detected this progressive brain disease in nearly half of the athletes we’ve studied who died before age 30.” Kneeland was in the middle of his second NFL season when he died on November 6, 2025. His case adds to a growing list of former players diagnosed posthumously with CTE.
CTE is a degenerative brain disease characterized by the progressive loss of nerve cells caused by repeated blows to the head. The condition can only be identified after death through brain analysis. It has been found not only in current and former professional athletes who competed in high-contact sports such as football and boxing, but also in military veterans and first responders. BU’s center notes that CTE is not limited to professional athletes; it has appeared in athletes who did not play sports beyond high school or college, with most young athletes displaying mild CTE. The disease progresses in stages from one to four, with four representing the most severe form.
People with CTE may experience a range of symptoms, including memory problems, confusion, impaired judgment, poor impulse control, aggression, depression, and even suicidal thoughts. In 2024, a Mass General Brigham study of nearly 2,000 former NFL players found that about one-third suspect they have CTE.
Numerous athletes have been diagnosed with the condition, including the Canton brothers John and Ed Grimsley. In 2023, BU’s CTE Center reported that among 376 former players studied, 91.7% were diagnosed with CTE posthumously. Separate research has highlighted heightened neurodegenerative risks for NFL players. A study conducted by Mass General Brigham, Boston University, and the Concussion & CTE Foundation and published in eClinicalMedicine on July 8, examined health data from 19,824 players who appeared in at least one professional game between 1960 and 2019. While overall all-cause mortality among these players was lower than in the general population, mortality from neurodegenerative diseases was markedly higher: dementia was 3.8 times more likely, and Parkinson’s disease 3.88 times more likely, among NFL players. The study also found that players with longer careers—defined as five seasons or more—had roughly double the risk of dying from a neurodegenerative disease compared with players with shorter careers.