What is CTE?
Chronic traumatic encephalopathy (CTE) is a brain disease linked to repeated hits to the head. Over time, an abnormal form of a protein called tau builds up around small blood vessels in the brain and spreads, damaging and killing nerve cells. The disease gets worse over years and can affect memory, thinking, mood and behavior.
In 2022 the National Institutes of Health formally recognized that CTE is caused by repeated traumatic brain injuries. (BU CTE Center, Oct. 2022)
Kevin Bieniek of Mayo Clinic’s Neurobiology of Disease program discusses a Mayo study of CTE in amateur athletes (Acta Neuropathologica, December 2015).
What causes it?
CTE is linked to repeated head impacts, not a single injury. Those hits don’t have to cause a concussion: research shows that many smaller, “subconcussive” hits can start the brain changes behind CTE. (Boston University, 2018)
Risk appears to rise with the number of years of exposure. Not everyone who takes repeated hits develops CTE, and scientists are still working out why some people do and others don’t. (Mayo Clinic; our research summaries)
Who is at risk?
CTE has been found most often in people with years of repeated head impacts: football, hockey, soccer, rugby and Australian rules football players, boxers and other combat-sport athletes, and military service members exposed to repeated blasts. It has been found in amateur and youth athletes as well as professionals, and in women as well as men. See Who is CTE for confirmed cases.
What are the symptoms?
Symptoms usually appear years or decades after the head impacts. People later found to have CTE have had:
- problems with memory, thinking and planning, sometimes progressing to dementia;
- changes in mood and behavior, such as depression, impulsiveness, aggression and emotional ups and downs;
- in some cases, movement problems similar to Parkinson’s disease.
None of these symptoms is unique to CTE, and many have other causes that can be treated. (Mayo Clinic)
How is CTE diagnosed?
Today CTE can only be confirmed by examining the brain after death. In living people, doctors can now use research criteria published in 2021 to identify traumatic encephalopathy syndrome, the pattern of symptoms associated with CTE, and to judge how likely it is that CTE is the cause. (Neurology, 2021)
Brain scans and blood tests that could detect CTE during life are being studied but are not yet ready for routine use. See Research for the latest.
Is there a cure or treatment?
There is no cure for CTE and no treatment proven to slow it. Many of the symptoms, such as depression, sleep problems and headaches, can be treated, so anyone with these symptoms should see a doctor. (Mayo Clinic)
Can CTE be prevented?
Because CTE is linked to repeated hits, researchers say the most important step is reducing the number of head impacts, especially for children and teens: limiting full-contact practice, teaching safer technique, and following return-to-play rules after any head injury. Helmets protect against skull fractures and other serious injuries and are essential, but they cannot stop every hit from jarring the brain. (Boston University, 2018)
Last reviewed October 2026. This page is for general information and is not medical advice. If you’re worried about your own symptoms or a loved one’s, please talk with a doctor.
