The problem is almost 100 years old and started in the ring
Chronic traumatic encephalopathy, or CTE, is not a recent discovery. In 1928, forensic pathologist Harrison Stanford Martland published in the Journal of the American Medical Association the description of 23 boxers who presented tremors, slowed movement, confusion and speech changes. He named the condition "punch drunk". The term later became "dementia pugilistica" and, finally, the current name: CTE.
In other words, the association between repeated blows to the head and progressive brain deterioration is one of the oldest links in sports medicine. What changed in the last two decades was the ability to look at brain tissue under the microscope and understand what exactly these blows leave behind.
What science has already proven about CTE
CTE is a tauopathy: a disease marked by the abnormal accumulation of phosphorylated tau protein in the brain. The characteristic lesion, considered the disease's signature, is the deposit of this protein around small blood vessels, at the depths of the cortical sulci. This differentiates it from other dementias and links it directly to repeated impacts to the head, not to a single traumatic blow.
The most uncomfortable finding of recent years came from a large study of young athletes. Ann McKee's team at Boston University examined the donated brains of 152 contact sport athletes who died before age 30. The result published in 2023 in JAMA Neurology: 63 of them, or 41%, already had CTE. And most never reached the professional level, they were school and university athletes.
The central message is that CTE pathology starts early. It is not exclusive to veterans of long careers. The biological signal appears earlier, silently, long before any clinical diagnosis.
The two sides: what the fight industry says
Here lies the controversy. Promoters and part of the MMA world argue, with some footing, that large-scale studies specifically in MMA are lacking. The sport is young as a regulated phenomenon, most fighters are still alive, and CTE can only be definitively confirmed by post-mortem brain examination. Therefore, they say, there is no way to state CTE rates in MMA with the same solidity as American football or boxing.
That point is technically correct. But it is often used for a conclusion that does not hold: that "there is no proof, therefore there is no risk". Absence of population studies is not absence of risk. Boxing has already demonstrated the mechanism. MMA shares the central factor: repeated impact to the head, including blows that continue after the knockout and on the ground.
What the best available evidence suggests in MMA
The most relevant study today comes from the partnership between UNLV and the Cleveland Clinic, the Professional Fighters Brain Health Study. In an analysis of 130 active and retired professional boxers and martial artists, published in 2023 in the journal Neurology, 52 of them (40%) met the criteria for traumatic encephalopathy syndrome, a clinical condition considered a possible precursor of CTE.
More than 80% of the fighters who met the criteria came from boxing, which reinforces the weight of impact volume over a career. And there is at least one case confirmed by autopsy in MMA: Jordan Parsons, a Bellator fighter who died at 25 in 2016 after being hit by a car. The post-mortem exam, whose result was released by Bennet Omalu, the pathologist who popularized the topic, found CTE. He was the first MMA fighter publicly diagnosed with the disease.
The symptoms: the human side of the damage
CTE does not manifest as one single thing. The consistent reports involve four major domains:
- Memory and cognition: forgetfulness, difficulty organizing tasks and slowed reasoning.
- Mood: depression, apathy and, worryingly, increased risk of suicide, the most common cause of death in the young athletes study.
- Personality and behavior: impulsivity, irritability and aggression.
- Motor: parkinsonism, tremors, gait and speech changes, the classic picture Martland was already describing in 1928.
The honesty the topic demands
It is necessary to be fair about what we still do not know. The dose-response relationship, that is, exactly how many blows, of what intensity and for how many years are needed to trigger the disease, is still under construction. Not every fighter develops CTE, and genetic and individual factors weigh in. Definitive diagnosis remains post-mortem only, and the in-life criteria, such as traumatic encephalopathy syndrome, are an approximation, not a verdict.
But the signal is consistent and comes from independent directions: the nearly century-long history in boxing, the biology of tauopathy linked to impact, the findings in young athletes and the neuroimaging data in living fighters. Downplaying this is not scientific skepticism, it is commercial convenience.
The reasonable conclusion is not "stop fighting". It is that athlete, coach and club need to treat the brain as the career's most valuable asset: controlling the volume of full-contact sparring, respecting return-to-play protocols after knockouts and concussions, and monitoring signs over the years. The risk is real. Ignoring it is a choice, not proof that it does not exist.
