Shocking Revelation: How CTE Took a Cowboys Legend

Updated July 7, 2026 11 min read

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Marshawn Kneeland CTE Diagnosis: Cowboys Defensive End Had Stage 1 Brain Disease at Age 24

TL;DR: Former Dallas Cowboys defensive end Marshawn Kneeland, who died by suicide in 2025 at the age of 24, was posthumously diagnosed with Stage 1 chronic traumatic encephalopathy (CTE), according to a brain analysis conducted by the Boston University CTE Center. The finding has reignited urgent conversations about head trauma in the NFL, the mental health struggles of young players, and the league’s ongoing responsibility to protect athletes long after they leave the field.

Marshawn Kneeland, a promising defensive end for the Dallas Cowboys, died by suicide at age 24, and a posthumous brain examination confirmed he had Stage 1 CTE. The diagnosis, announced in mid-2026, has sent shockwaves through the NFL community and raised new questions about how head injuries affect even the youngest professional football players.

Quick Answer

Marshawn Kneeland, a former Dallas Cowboys defensive end, was diagnosed with Stage 1 CTE (Chronic Traumatic Encephalopathy) following his death by suicide at age 24. The diagnosis was confirmed through brain tissue analysis, and it has renewed calls for better player safety, mental health resources, and long-term monitoring of NFL athletes exposed to repetitive head trauma.

Who Was Marshawn Kneeland?

Marshawn Kneeland was a defensive end for the Dallas Cowboys who entered the NFL with high expectations. Standing out for his athleticism and pass-rushing ability, Kneeland represented the next wave of talent on the Cowboys’ defensive line. His career was cut short by his tragic death at age 24, one of the youngest NFL players to receive a posthumous CTE diagnosis in recent years.

Kneeland played college football before being drafted by the Dallas Cowboys, where he became a key rotational player on their defense. Those who knew him described a young man with immense potential both on and off the field. His death left teammates, coaches, and the broader NFL community mourning a life that ended far too soon.

What Is CTE and Why Does It Matter for NFL Players?

Defining Chronic Traumatic Encephalopathy (CTE)

Chronic Traumatic Encephalopathy (CTE) is a progressive degenerative brain disease found in individuals with a history of repetitive brain trauma. The disease is characterized by the buildup of an abnormal protein called tau, which forms clumps that slowly kill brain cells. CTE can only be definitively diagnosed posthumously through examination of brain tissue.

According to the Boston University CTE Center, which conducts the majority of CTE research in the United States, the disease has been found in the brains of hundreds of former professional football players. The condition is associated with memory loss, confusion, impaired judgment, aggression, depression, anxiety, suicidality, parkinsonism, and eventually progressive dementia.

Stage 1 CTE: What Marshawn Kneeland’s Diagnosis Means

CTE is classified into four stages of severity. Kneeland’s diagnosis of Stage 1 CTE represents the earliest identified phase of the disease. Stage 1 CTE is characterized by mild symptoms that may include headaches, concentration and memory difficulties, mood changes, and impulse control problems. While Stage 1 is the least severe classification, the fact that it was present in a 24-year-old underscores how early repetitive head trauma can begin altering brain structure.

Research shows that CTE progression is not strictly tied to age or years of exposure. Some individuals develop the disease after relatively fewer years of contact sports, suggesting that genetic factors and the intensity of head impacts play significant roles in susceptibility.

CTE Stages and Associated Symptoms
Stage	Severity	Primary Symptoms	Brain Changes
Stage 1	Mild	Headaches, attention difficulty, mood swings, impulse control issues	Tau deposits in small, focal areas
Stage 2	Moderate	Depression, anxiety, short-term memory loss, suicidality	More widespread tau deposits, affecting multiple brain regions
Stage 3	Severe	Aggression, paranoia, severe memory loss, difficulty with daily tasks	Significant neuronal loss, expanded tau pathology
Stage 4	Most Severe	Full-blown dementia, inability to perform basic functions, motor impairment	Extensive tau pathology resembling Alzheimer’s disease

How Did Marshawn Kneeland Get CTE?

Repetitive Head Trauma in Football

The primary cause of CTE in NFL players is repetitive subconcussive impacts — head hits that do not necessarily cause a diagnosed concussion but still damage the brain over time. Studies conducted by Boston University and the National Institutes of Health (NIH) indicate that it is the cumulative exposure to head impacts, rather than individual catastrophic injuries, that drives CTE development.

For a player like Kneeland, who played the high-impact position of defensive end, the volume of head contact during practices, games, and even offseason training would have been substantial. Research published in the Journal of the American Medical Association (JAMA) found that football players can sustain hundreds or even thousands of subconcussive impacts per season, depending on their position and role.

The Unique Risk for Young Players

Kneeland’s diagnosis at age 24 is particularly alarming because the developing brain is more vulnerable to trauma. According to the CTE Center at Boston University, individuals who begin playing tackle football before age 12 face a significantly higher risk of developing CTE later in life. The younger the brain at the time of initial exposure, the more susceptible it appears to the degenerative effects of repetitive trauma.

This finding has prompted advocacy groups and medical researchers to push for limiting contact in youth football, delaying tackle football participation, and improving helmet technology at every level of the sport.

The Mental Health Dimension: CTE, Depression, and Suicide

CTE is strongly linked to mental health struggles, including depression, anxiety, irritability, and suicidal ideation. According to research from Boston University, individuals diagnosed with CTE are significantly more likely to experience clinical depression and suicidal behavior compared to the general population. In Kneeland’s case, the presence of Stage 1 CTE may have contributed to mental health challenges that ultimately proved fatal.

The NFL Players Association (NFLPA) has acknowledged the mental health crisis among current and former players. The league introduced expanded mental health programs in 2019 following a series of player suicides, including those of Junior Seau, Dave Duerson, and Aaron Hernandez. However, critics argue these programs remain insufficient in scope and accessibility, particularly for younger players who may feel stigmatized seeking help.

For more information, see our guide on NFL player mental health resources and support programs.

NFL’s Response to the Marshawn Kneeland CTE Diagnosis

What the League Has Said

The NFL and the Dallas Cowboys have issued statements acknowledging Kneeland’s diagnosis and expressing condolences to his family. The league reiterated its commitment to funding independent CTE research and improving player safety protocols. The NFL has invested over $100 million in brain injury research and safety technology since 2016, according to league officials.

However, advocacy groups, including the Concussion Legacy Foundation and the Brain Injury Research Institute, have argued that the NFL’s response continues to fall short of what the science demands. They point to ongoing issues with practice protocols, the speed and violence of the modern game, and inadequate long-term care for retired players as evidence that systemic change is still needed.

Calls for Stronger Action

Following the announcement of Kneeland’s diagnosis, several prominent voices in the sports world called for more aggressive measures. These include:

Mandatory long-term neurological monitoring for all active NFL players, beginning in their first year
Expanded baseline testing using advanced neuroimaging technology, not just standard concussion assessments
Greater transparency from the NFL about the results of its own internal research on head trauma
Increased funding for mental health services specifically tailored to young players transitioning out of football
Reevaluation of practice contact rules, including limits on full-contact sessions during the regular season

How CTE Is Changing Football at Every Level

Youth and High School Football Reforms

The awareness generated by high-profile CTE diagnoses like Kneeland’s has accelerated reforms at youth and high school levels. Several states have enacted legislation limiting full-contact practices for high school athletes, and organizations like USA Football have promoted “Heads Up Tackling” programs designed to teach safer contact techniques. Despite these efforts, participation in youth tackle football has declined steadily since 2010, according to data from the Sports & Fitness Industry Association, as parents weigh the risks against the benefits.

Advances in Helmet Technology and Concussion Protocols

Equipment manufacturers, including Riddell and Schutt, have developed helmets with improved impact-absorbing materials designed to reduce both concussive and subconcussive forces. The NFL has also partnered with engineering firms to test and approve next-generation helmets, creating an annual helmet performance ranking that encourages innovation. Despite these advances, researchers caution that no helmet can fully eliminate the risk of CTE, since the disease is driven primarily by the brain’s movement within the skull rather than direct external impact.

Notable NFL Players Diagnosed with CTE

Kneeland’s case is part of a larger and deeply troubling pattern. According to Boston University’s CTE Center, as of its most recent data, CTE has been found in 345 of 376 NFL brains examined — a prevalence rate exceeding 91%. Some of the most prominent cases include:

Notable NFL Players Diagnosed with CTE
Player	Position	CTE Stage	Age at Death	Cause of Death
Junior Seau	Linebacker	Stage 4	43	Suicide (gunshot)
Aaron Hernandez	Tight End	Stage 3 (severe)	27	Suicide (hanging)
Dave Duerson	Safety	Stage 4	50	Suicide (gunshot)
Frank Gifford	Running Back / Wide Receiver	Stage 4	84	Natural causes
Ken Stabler	Quarterback	Stage 2	69	Colon cancer
Marshawn Kneeland	Defensive End	Stage 1	24	Suicide

What Can Be Done to Prevent CTE?

Current Research and Prevention Efforts

Scientists are actively studying CTE to understand why some individuals develop the disease while others with similar exposure do not. Key areas of research include genetic risk factors, the role of tau protein accumulation, and potential biomarkers that could allow for living diagnosis of CTE — something that is currently impossible with standard imaging.

The National Institute of Neurological Disorders and Stroke (NINDS), a division of the NIH, has funded multiple CTE studies exploring diagnostic techniques, including advanced PET scans and spinal fluid analysis. If successful, these tools could transform the ability to detect and potentially treat CTE before it progresses to severe stages.

Steps Players Can Take to Protect Brain Health

While eliminating all risk is impossible in contact sports, medical experts recommend several strategies for current and former players:

Participate in baseline neurological testing and maintain regular cognitive assessments throughout and after a football career
Report all symptoms of concussion or cognitive decline immediately — early intervention improves outcomes
Seek mental health support proactively, not only during crises, to address mood and behavioral changes that may signal neurological changes
Reduce unnecessary head impacts during practice by advocating for modified training techniques within team programs
Stay informed about emerging research on CTE prevention, treatment, and biomarker development

Key Takeaways

Marshawn Kneeland, a former Dallas Cowboys defensive end, was posthumously diagnosed with Stage 1 CTE at age 24 following his death by suicide.
Stage 1 CTE represents the earliest phase of the degenerative brain disease, characterized by mood changes, memory difficulties, and impulse control issues.
Repetitive subconcussive head impacts — not just diagnosed concussions — are the primary driver of CTE in football players.
Boston University research shows CTE has been found in over 90% of NFL brains examined, highlighting the systemic nature of the problem.
The diagnosis has intensified calls for mandatory neurological monitoring, expanded mental health resources, and stricter safety protocols at all levels of football.

Conclusion

The posthumous CTE diagnosis of Marshawn Kneeland represents one of the youngest confirmed cases of the brain disease in NFL history and serves as a stark reminder that chronic traumatic encephalopathy does not discriminate by age. At just 24 years old, Kneeland’s Stage 1 CTE diagnosis reveals how quickly repetitive head trauma can alter brain structure in young athletes. The findings amplify existing demands for the NFL to expand its player safety initiatives, invest in long-term neurological monitoring, and dismantle the cultural stigma that prevents players from seeking mental health support. As research into CTE diagnosis and prevention continues to advance, cases like Kneeland’s carry the weight of evidence that the sport’s leaders must act with greater urgency — and that the cost of inaction continues to be measured in young lives lost.

Frequently Asked Questions

What is CTE and how is it diagnosed?

CTE (Chronic Traumatic Encephalopathy) is a progressive brain disease caused by repetitive head trauma. It can only be definitively diagnosed posthumously through examination of brain tissue, which reveals the presence of an abnormal tau protein. Researchers at Boston University currently conduct the majority of CTE diagnoses in the United States.

Did Marshawn Kneeland have Stage 1 CTE?

Yes. According to NBC Sports and multiple outlets including ESPN and USA Today, Marshawn Kneeland’s posthumous brain analysis confirmed Stage 1 CTE, the earliest and mildest stage of the degenerative disease.

Can CTE be detected in living patients?

Currently, CTE cannot be definitively diagnosed in living individuals. Researchers are actively developing PET scan techniques and spinal fluid biomarker tests that may eventually allow for a living diagnosis, but these methods remain in the research phase as of 2026.

What causes CTE in football players?

CTE in football players is primarily caused by repetitive subconcussive head impacts — thousands of smaller hits to the head that occur during practices and games. Research from Boston University indicates it is the cumulative exposure to these impacts, rather than single concussion events, that drives the development of CTE.

How many NFL players have been diagnosed with CTE?

According to the Boston University CTE Center, as of its most recent data, CTE has been found in approximately 91% (345 out of 376) of NFL brains donated for examination. The high prevalence rate has made CTE one of the most pressing public health concerns in professional sports.

What is the NFL doing to address CTE?

The NFL has invested over $100 million in brain injury research and safety technology, implemented stricter concussion protocols, created practice contact limitations, and partnered with equipment manufacturers to develop safer helmets. Critics argue these measures remain insufficient given the scale of the problem.

At what age can CTE begin to develop?

CTE can begin developing from the earliest stages of repetitive head trauma exposure. Research shows that individuals who start playing tackle football before age 12 face elevated risk, and CTE pathology has been found in brains of individuals as young as their early twenties, as the Marshawn