Concussions in American football

Lore & Background

The NFL's MTBI Committee, chaired by rheumatologist Elliot Pellman, faced criticism for lacking neurological expertise. The committee published studies from 2003 stating no long-term negative health consequences from concussions, contradicting findings from the National Institute for Occupational Safety and Health (NIOSH) and the Center for the Study of Retired Athletes. A 2004 doctoral dissertation by Don Brady found that many NFL players lacked accurate concussion knowledge, and that sports health-care personnel should prioritize athlete health over performance.

Reader's Guide

Concussions in American football have become a central public health issue, with evidence linking repeated head impacts to chronic traumatic encephalopathy (CTE), a degenerative brain disease found in athletes and others with repetitive brain trauma. The NFL and NFLPA now maintain concussion protocols including preseason education, baseline assessments, and staged return-to-play procedures. Despite helmet improvements, the CDC states no helmet can prevent every concussion. A 2017 study found 99% of tested NFL brains had CTE, while a 2026 observational study of 6,201 NFL players found no statistically significant association between documented concussions and arrests after excluding pre-concussion arrests. The disease remains controversial and misunderstood, with tau protein clumps believed to kill brain cells, and theoretical research suggesting damaged blood vessels may trigger inflammation. The NFL reported a 17% reduction in recorded concussions in 2024 compared to 2023, the lowest since 2015.

Did You Know?

• A 2017 study found 99% of tested NFL brains, 88% of CFL brains, and 21% of high school football brains had various stages of CTE.
• The NFL's MTBI Committee was chaired by a rheumatologist, not a neurologist, and its data from 1996 to 2001 undercounted diagnosed concussions by approximately 90%.
• The CDC states that evidence is insufficient to conclude that occasional impacts or a history of one or more concussions alone lead to CTE.

The Long Shadow of CTE

CTE is a progressive brain degeneration that Boston University researchers have linked to repetitive head trauma in athletes, military veterans, and others. The working model holds that tau proteins accumulate into clumps that gradually spread across brain tissue, ultimately destroying cells. The clinical aftermath for former players is severe: memory loss, depression, anxiety, persistent headaches, heightened stress, and disrupted sleep have all been reported among those affected. The scale of the problem is staggering. A 2017 post-mortem study of deceased gridiron football players found CTE at various stages in 99 percent of NFL brains, 88 percent of CFL brains, 91 percent of college players, 64 percent of semi-professional athletes, and even 21 percent of high school players. The roster of ex-NFL athletes either confirmed post-mortem or self-reporting CTE-like symptoms keeps expanding. The CDC cautions that definitive diagnosis still requires examining the brain after death and that the exact set of symptoms directly attributable to CTE remains uncertain, yet the pattern of long-term exposure to repeated head impacts as a risk factor is well established.

Protocols and the Push to Reduce Head Impacts

The NFL and its players' union have built a multi-layered system for handling suspected concussions. Before the season begins, players receive education and undergo baseline neurological testing. During games, club medical personnel coordinate with independent neurotrauma consultants and athletic trainers stationed in the booth to watch for signs of head injury. A player showing concussion symptoms is pulled from the action for evaluation, and if a diagnosis is confirmed, same-day return is prohibited. Recovery follows a five-phase progression starting with limited, symptom-free activity and building toward full-contact football. There is no set number of days; advancement depends entirely on how the individual responds clinically. Before full clearance, the club physician must sign off, and that decision is then verified by an independent neurological consultant. In January 2025, the league announced that recorded concussions across the 2024 preseason and regular season dropped 17 percent compared with 2023, marking the lowest total since electronic medical records were adopted in 2015. The league and union also publish helmet rankings derived from laboratory testing, though the CDC reminds the public that while helmets lower the risk of serious head injury, no helmet can block every concussion.

A Decades-Long Pattern of Denial

Concerns about head injuries in football date to the early 1900s. In 1906, a Harvard student-athlete died from a head blow in play, and the team's medical staff published a report in the Boston Medical and Surgical Journal cataloguing the types, severity, and number of injuries from the 1905 season. Yet the NFL did not formally examine the issue until 1994, when Commissioner Paul Tagliabue established the Mild Traumatic Brain Injury Committee. He appointed rheumatologist Elliot Pellman to chair it, a choice that drew sharp criticism because Pellman was neither a neurologist nor a neuropsychologist and often admitted ignorance about head injuries. Data the league collected between 1996 and 2001 has since been shown to undercount actual concussions by roughly ten percent. Compounding the problem, the league relied on legal counsel who had been active in downplaying health risks in the tobacco industry. That same year, the National Institute for Occupational Safety and Health reported a statistically significant rise in neurological disorders, including amyotrophic lateral sclerosis, among retired football players. Pellman and his committee nonetheless issued conclusions that contradicted those findings. Biomechanical engineers and neurosurgeons warned the committee that the helmet safety standard was inadequate to minimize concussion risk.

The Science of Brain Trauma

Beyond the well-known tau protein model, researchers are exploring additional pathways by which repeated head impacts may damage the brain. One line of theoretical work suggests that early CTE could originate in damaged blood vessels within the brain, triggering inflammation that eventually promotes the formation of tau and other proteins implicated in the disease. To test this hypothesis, scientists used a specialized device to deliver precise, controlled impacts to adult mice, producing mild brain trauma comparable to what athletes experience in contact sports. Because mouse brains share key attributes with human brains, the researchers considered the model relevant. Specialized MRI scans revealed that the mice's brains showed immediate changes in electrical function following the impacts. The CDC has noted that CTE is associated with long-term exposure to repeated head impacts, but that the evidence is insufficient to conclude that occasional impacts or even a history of one or more concussions alone cause the disease. The agency also emphasizes that the full set of symptoms directly attributable to CTE remains uncertain and that a definitive diagnosis can only be confirmed through examination of the brain after death.

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