Chronic Traumatic Encephalopathy (CTE): What It Is, Why It Develops, and How Symptoms Get Managed

Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026

Quick answer

Chronic traumatic encephalopathy (CTE) is a degenerative brain disease caused by repeated head injuries, with abnormal tau protein buildup and permanent brain damage [1] [2]. It mostly affects former football players, boxers and military veterans [1]. Symptoms include mood swings, depression, memory loss and later dementia [1]. It can only be confirmed after death, has no cure, and treatment focuses on managing symptoms [1] [2].

What the research says

According to PubMed:

• More years of exposure means more risk. A 2025 review reports that studies in American football, rugby, and ice hockey players show a dose-response relationship between years of exposure to the sport and CTE risk and severity. The defining lesion is a perivascular buildup of hyperphosphorylated tau at the depths of cortical sulci, and CTE can be diagnosed only by examining the brain after death. (Babcock et al., American Journal of Pathology, 2025) [2].

• Researchers have defined the clinical syndrome, but only for research. A panel of 20 expert clinician-scientists reached consensus over 4 Delphi rounds on criteria for traumatic encephalopathy syndrome (TES), the clinical disorder associated with CTE: substantial repetitive head impact exposure, core cognitive or neurobehavioral features, a progressive course, and no better explanation from another condition. The criteria were built to support CTE research, not as a routine diagnosis. (Katz et al., Neurology, 2021) [3].

What is chronic traumatic encephalopathy?

Chronic traumatic encephalopathy (CTE) is a neurodegenerative brain disease that can develop after extensive repeated impacts or blows to your head [1] [2]. "Neurodegenerative" means it slowly damages and breaks down brain tissue over time. CTE most commonly affects former football players and boxers, along with military veterans — people whose careers or service involved repeated hits to the head [1].

CTE involves permanent brain damage that can change your behavior and mental abilities [1]. You may have mood swings, or struggle with problem-solving and memory. The damage and symptoms get worse with time.

There's an unusual feature that sets CTE apart: you can't get an official CTE diagnosis while you're alive. Scientists must look at brain tissue under a microscope after death [1] [2]. Your provider might suspect CTE during life, but its symptoms overlap with many other conditions that they'll need to consider.

Key fact	What it means
Official diagnosis	Only possible after death, by examining brain tissue under a microscope during an autopsy
Probable diagnosis	While alive, a provider can build a probable diagnosis from exams, symptoms, and history of head injuries
Reversibility	Not reversible — the brain damage is permanent
Progression	Gradual — changes happen slowly, over years or even decades

What CTE is, how a CTE brain differs from a healthy brain, and why it's confirmed only after death.

What are the symptoms of CTE?

CTE shares symptoms with other brain diseases that cause neurodegeneration. It can affect your mood, thinking, memory, and movement [1].

Symptom	What it looks like
Headaches	Recurring head pain
Mood swings	Especially anger and impulsiveness
Depression	Persistent low mood
Personality changes	Acting differently, sometimes "not like yourself"
Memory loss	Forgetting things more often than usual
Executive dysfunction	Trouble solving problems, making plans, or deciding
Balance issues	Unsteadiness when standing or walking
Loss of coordination	Clumsiness, difficulty with precise movements
Tremors and twitches	Muscle movements you can't control
Dementia	In late-stage cases

It can be hard to know whether these symptoms are due to CTE or another condition. Either way, it's worth seeing your provider if you notice these changes.

What causes CTE?

Extensive exposure to repeated head injuries (RHI), usually over many years, causes CTE. Here a "head injury" means any impact that makes your brain shake within your skull, not just hard knockouts [1]. RHI may include:

Type of impact	Description
Mild hits	Hits that don't cause any symptoms
Concussions	A temporary change in brain function after a hit to the head
Traumatic brain injuries (TBIs)	More severe injuries that can damage brain structures

An impact distorts brain tissue and strains fragile structures in the grooves of your brain, and these effects build up over time with repeated impacts [2]. Researchers think RHI causes a buildup of abnormal tau proteins. Tau proteins help your brain cells keep their shape, but if repeated head hits damage your cells, tau may lose its normal structure and form tangled clusters [1]. Experts are still studying exactly why CTE happens in some people but not others.

Who is at risk for CTE?

CTE risk rises with situations that cause repeated hits to the head, and the more head injuries a person has over time, the more likely CTE becomes [1] [2].

Situation	Examples
Contact sports	American football, ice hockey, rugby
Combat sports	Boxing, mixed martial arts (MMA), traditional martial arts
Military service	Combat exposure and blast-related impacts
Domestic violence	Repeated blows to the head
Severe head-banging behavior	Repeated self-directed head impacts

The more head injuries you have over time, the more likely you are to develop CTE, and some experts think certain genes may raise risk [1]. Research in football, rugby, and ice hockey players supports this dose-response pattern (Babcock et al., 2025). Avoiding head injuries is the only way to lower your risk. Wear the right protective equipment for all activities and sports, especially helmets or protective headwear.

How repeated head impacts damage the brain, and who is at risk of CTE.

How do doctors diagnose CTE?

CTE cannot be diagnosed while a person is alive, but a provider can build a probable diagnosis from symptoms and tests that rule out other conditions. Healthcare providers can only confirm it by looking at brain samples under a microscope, which is possible only during an autopsy after someone dies [1] [2]. Even so, your provider can make an educated assessment and build a probable diagnosis from:

Factor	What it contributes
Physical exam	Overall health assessment
Neurological exam	Tests of nerves, reflexes, and brain function
Symptoms and changes	What you and your loved ones are experiencing
Medical history	Especially any known head injuries

Having CTE-like symptoms doesn't automatically mean you have CTE, because many other conditions look similar [1]. Your provider will use various tests to help diagnose or rule out other conditions. For research purposes, experts have also proposed criteria for traumatic encephalopathy syndrome (TES), the clinical picture associated with CTE (Katz et al., 2021; Wallingford and Junn, 2024).

What does a brain with CTE look like?

Brain change	What happens
Cerebral cortex atrophy	Shrinking of the outermost layer of the brain, especially in the front and sides
Corpus callosum thinning	Thinning of the tissue that connects the right and left sides of the brain
Tau clusters	Brownish tangles around tiny blood vessels deep in the brain's grooves

How severe can CTE get?

During an autopsy, pathologists assign a stage of CTE based on the type and amount of damage in brain tissue [1]. The stages range from stage I through IV, from mild to severe.

How is CTE treated?

CTE cannot be treated directly because brain damage cannot be reversed, so providers focus on ways to manage the symptoms [1]. Instead, they'll suggest ways to manage symptoms:

Treatment	What it helps with
Cognitive rehabilitation therapy	Improving mental functions such as memory and attention
Talk therapy	Mood swings and coping with CTE symptoms
Occupational therapy	Making everyday tasks easier
Physical therapy	Movement issues
Medications	Symptoms that linger despite other types of therapy

Experts are still researching CTE. Ask your provider about clinical trials you might be able to join, which may let you try new or experimental treatments [1].

CTE symptoms to watch for and how they are managed.

What is the outlook for CTE?

The brain damage from CTE is permanent, and the symptoms get worse over time [1]. These changes tend to happen slowly, over years or even decades [1]. Over time, you may develop dementia and lose the ability to feed, bathe, or dress yourself [1]. If symptoms keep worsening, you may want to think about future planning, such as an advance directive and legal and financial plans, and your healthcare team can help [1]. Researchers are still studying whether CTE directly affects life expectancy [1].

How can I lower my risk?

Avoiding head injuries is the only way to lower your risk of CTE [1]. Wear the right protective equipment for all activities and sports, especially helmets or protective headwear. The more head injuries you avoid, the more you protect yourself.

Is there reassurance for people worried about chronic traumatic encephalopathy (CTE)?

CTE can be a confusing condition. It might be hard to understand how it can have such a big impact on your health and life if providers can't confirm you have it. But it's real, and so are its symptoms. At first you may not notice some of the symptoms in yourself. Loved ones might tell you you're acting differently or "not like yourself." Try to remember that people who care about you share these concerns because they want you to be safe and healthy. See a healthcare provider or a mental health professional for guidance.

What's the bottom line?

Chronic traumatic encephalopathy is a serious condition tied to years of repeated hits to the head, and the hardest part is that it can't be officially confirmed until after death [1] [2]. But the symptoms people experience while living are real and deserve attention. If you've played contact or combat sports, served in the military, or had many head injuries, and you or your loved ones notice changes in mood, memory, or movement, the most important step is to see a healthcare provider. A probable diagnosis can guide symptom management, and therapies like cognitive rehabilitation, talk therapy, and medications can improve day-to-day life [1]. Prevention — wearing helmets and limiting head impacts — remains the only way to lower your risk [1].

Ready to learn more? Visit Rinnit.com for trusted, easy-to-understand health guides like this one.

Conclusion

Living with the uncertainty of a condition that can't be confirmed in life is hard, both for the person affected and for the people who love them. What you can do is take changes in mood, thinking, and movement seriously, protect your head, and lean on a healthcare team that can help manage symptoms and plan ahead.

Find more compassionate, plain-English health guides at Rinnit.com.

Frequently Asked Questions

What is chronic traumatic encephalopathy (CTE)?

CTE is a neurodegenerative brain disease caused by extensive repeated impacts or blows to the head, usually over many years. It involves permanent brain damage that changes behavior and mental abilities and gets worse over time.

Who gets CTE?

CTE most commonly affects former football players and boxers, along with military veterans, which means people with years of repeated hits to the head.

Can CTE be diagnosed while you're alive?

No. CTE can only be confirmed by examining brain tissue under a microscope after death. While alive, a provider can build a probable diagnosis from exams, symptoms, and your history of head injuries.

What does CTE feel like?

Symptoms can include headaches, mood swings (especially anger and impulsiveness), depression, personality changes, memory loss, trouble solving problems or making plans, balance issues, loss of coordination, tremors, and dementia in late-stage cases.

What causes CTE?

Extensive exposure to repeated head injuries over many years. A "head injury" here means any impact that makes your brain shake within your skull, including mild hits that cause no symptoms, concussions, and traumatic brain injuries.

Can one concussion cause CTE?

CTE is linked to extensive repeated head injuries over many years rather than a single event. The effects build up over time with repeated impacts.

What happens to the brain in CTE?

The outer layer of the brain (cerebral cortex) shrinks, especially in the front and sides, the tissue connecting the two halves of the brain (corpus callosum) thins, and brownish tau clusters form around tiny blood vessels deep in the brain's grooves.

What are tau proteins?

Tau proteins help brain cells keep their shape. Researchers think repeated head hits damage brain cells so that tau proteins lose their normal structure and build up abnormally.

How severe can CTE get?

Pathologists assign stages I through IV during an autopsy, from mild to severe. In late stages, people may develop dementia and lose the ability to feed, bathe, or dress themselves.

Is there a cure for CTE?

No. There's no way to reverse brain damage. Treatment focuses on managing symptoms with therapies and medications.

How is CTE treated?

Providers suggest symptom management: cognitive rehabilitation therapy for memory and attention, talk therapy for mood swings and coping, occupational therapy for everyday tasks, physical therapy for movement issues, and medications for symptoms that linger.

Can I join a CTE research study?

Experts are still researching CTE. Ask your provider about clinical trials you might be able to join, which may let you try new or experimental treatments.

Does CTE affect life expectancy?

Researchers are still studying whether CTE directly affects life expectancy.

How is CTE different from a concussion?

A concussion is a temporary change in brain function after a hit to the head. CTE is a progressive, permanent brain disease that develops after many repeated head injuries over years.

What are the risk factors for CTE?

Situations with repeated hits to the head: contact sports (American football, ice hockey, rugby), combat sports (boxing, MMA, martial arts), military service, domestic violence, and severe head-banging behavior. The more head injuries over time, the more likely CTE becomes.

Can genes affect CTE risk?

Some experts think certain genes may increase CTE risk, and experts are still studying why CTE happens in some people but not others.

How can I lower my risk of CTE?

Avoiding head injuries is the only way to lower your risk. Wear the right protective equipment for all activities and sports, especially helmets or protective headwear.

My loved one says I'm "not myself." Could it be CTE?

Personality changes can have many causes. It's worth seeing your provider, who can build a probable diagnosis and help rule out other conditions.

Why do loved ones notice symptoms before I do?

At first, you may not notice some symptoms in yourself. Loved ones share concerns because they want you to be safe and healthy. See a healthcare provider or a mental health professional for guidance.

What should I do if symptoms keep getting worse?

Talk with your healthcare team about future planning, such as an advance directive and legal and financial plans. They can help you plan.

This article is for general informational purposes only and does not constitute medical advice, diagnosis, or treatment. Always seek the guidance of your physician or other qualified health provider with any questions about a medical condition. Never disregard professional medical advice or delay seeking care because of something you have read here. If you think you may have a medical emergency, call your local emergency number immediately.

References

1. Cleveland Clinic. Chronic Traumatic Encephalopathy (CTE). Cleveland Clinic. Last updated July 27, 2026. https://my.clevelandclinic.org/health/diseases/17686-chronic-traumatic-encephalopathy-cte

2. Babcock KJ, Abdolmohammadi B, McKee AC. Recent Advances in Chronic Traumatic Encephalopathy. Am J Pathol. 2025;195(11):2048-2058. PMID 40784657. https://doi.org/10.1016/j.ajpath.2025.07.008

3. Katz DI, Bernick C, Dodick DW, et al. National Institute of Neurological Disorders and Stroke Consensus Diagnostic Criteria for Traumatic Encephalopathy Syndrome. Neurology. 2021;96(18):848-863. PMID 33722990. https://doi.org/10.1212/WNL.0000000000011850

4. Wallingford A, Junn C. Chronic Traumatic Encephalopathy. Phys Med Rehabil Clin N Am. 2024;35(3):607-618. PMID 38945654. https://doi.org/10.1016/j.pmr.2024.02.011