Chronic traumatic encephalopathy, or CTE, is a brain disease linked to repeated hits to the head, often seen in military veterans and athletes.

CTE cannot be diagnosed until the patient has died and their brain examined. But doctors said there are symptoms such as changes in cognition, mood and behavior. The American Brain Foundation said they can include difficulty thinking, short- and/or long-term memory loss, depression, anxiety, paranoia, headaches and suicidal thoughts or behavior.

According to the Mayo Clinic, CTE — or chronic traumatic encephalopathy — is a brain disease most likely caused by repeated head injuries that damage the brain's nerve cells. The Mayo Clinic notes the only way to tell for sure if someone suffered from CTE is by autopsy.