The posthumous diagnosis of former Dallas Cowboys defensive end Marshawn Kneeland with Stage 1 chronic traumatic encephalopathy (CTE) has renewed interest in one of sport's most widely discussed brain diseases.
Boston University's CTE Center confirmed the diagnosis after Kneeland's family donated his brain for research following his death in November 2025 at the age of 24.
While the findings have prompted fresh questions about what chronic traumatic encephalopathy is, its symptoms, causes and whether there is a cure, researchers have stressed that a CTE diagnosis should not be viewed as the direct cause of suicide.
Kneeland's Stage 1 CTE Diagnosis Explained
Boston University's CTE Center announced that Kneeland had Stage 1 CTE, the earliest of four recognised stages of the progressive brain disease. The diagnosis came after his family chose to donate his brain to help researchers better understand the long-term effects of repeated head impacts.
In a statement released on Tuesday, Kneeland's family said: 'While this diagnosis does not change the tragedy of his passing, it provides important context about some of the struggles he may have been facing.
'We share this information to help people understand what NFL and other high contact sport athletes might be struggling with. Raising awareness is important to us. We continue to remember Marshawn with compassion for the person he was, rather than defining him by the final moments of his life. One Love.'
The Boston University CTE Center also emphasised that suicide is 'complex and multifactorial' and said that a posthumous CTE diagnosis should not be considered the cause of suicide.
Dr Ann McKee, director of the Boston University CTE Center and chief of neuropathology for the VA Boston Healthcare System, said she was not surprised by the findings.
'We have found this progressive brain disease in nearly half of the athletes we've studied who have died before the age of 30,' McKee said, adding that ongoing research is improving understanding of the earliest stages of CTE.
CTE Symptoms and Causes
Chronic traumatic encephalopathy is a progressive brain disease associated with repeated head impacts, particularly in contact sports such as American football, boxing and rugby. Researchers believe repeated blows to the head can trigger abnormal changes in the brain over time, although not every athlete exposed to repeated head trauma develops CTE.
One of the challenges surrounding CTE is that it can currently only be definitively diagnosed after death through examination of brain tissue.
Symptoms may not appear until years after repeated head injuries and can vary from person to person. Commonly reported CTE symptoms include memory loss, difficulty concentrating, confusion, impaired judgement, mood changes, depression, impulsive behaviour and aggression.
Researchers continue to study why some athletes develop the disease while others with similar exposure to head impacts do not. Factors such as the number and severity of head injuries, genetics and other health conditions remain under investigation.
Is There a Cure for CTE?
There is currently no cure for chronic traumatic encephalopathy. Existing treatment focuses on managing symptoms and improving quality of life rather than reversing the underlying brain damage.
Researchers are working to develop methods that could diagnose CTE during a person's lifetime, which could lead to earlier intervention and more targeted care. According to McKee, ongoing studies at Boston University's CTE Center are bringing scientists closer to diagnosing the disease in living patients while continuing the search for effective treatments and, ultimately, a cure.
Kneeland's Mental Health History
According to records obtained by ESPN, concerns about Kneeland's mental health dated back to 2020 while he attended Western Michigan. In one incident, he surrendered a firearm to police until he was cleared by a counsellor.
In another, authorities responded after a friend reported concerns for his wellbeing and found him on railway tracks, where he said he hoped a train would hit him. He was later hospitalised.
Texas authorities found Kneeland dead on 6 November 2025 after he allegedly fled from police during a high-speed pursuit, crashed his vehicle and ran from the scene. Officers had also received information that he had expressed suicidal thoughts before his death.
Boston University's CTE Center reiterated that mental health crises and suicide involve multiple contributing factors and should not be attributed solely to a diagnosis of CTE.
