With CTE back in the headlines, and affecting athletes from range of sports, here are seven things to know about the brain disease
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Former San Francisco 49ers player Jason Hairston, who died by suicide this week, believed he exhibited symptoms of CTE, a brain disease that has been diagnosed in many deceased professional football players.

CTE can only be diagnosed after death, and in a 2017 study of the brains of 111 deceased NFL players, a Boston University researcher found that 110 of them had the disease.

With CTE back in the headlines, here are seven things to know about the brain disease.

What is CTE?
CTE, or chronic traumatic encephalopathy, is a rare and progressive degenerative brain condition likely caused by repeated head traumas, according to the Mayo Clinic.

What causes CTE?
CTE is caused by repeated concussions and traumatic brain injuries. The disease has been found mostly in athletes who play contact sports, members of the military and victims of physical abuse, though not everyone who experiences repeated concussions goes on to develop CTE.

What are the symptoms?
The symptoms of CTE include difficulty thinking, depression, impulsive behavior, short-term memory loss and emotional instability. Irritability, aggression, speech difficulties, trouble swallowing and vision problems may also be signs of the condition.

When should you see a doctor if you think you might have CTE?
People experiencing suicidal thoughts, memory problems, personality or mood changes and head injuries should seek medical attention.

How is CTE diagnosed?
Currently, CTE can only be definitively diagnosed after death when the brain can be examined for the toxic protein TAU, according to the Concussion Legacy Foundation. Research to develop a test for CTE that can be used while people are alive is currently ongoing.

How can CTE be treated?
There is no treatment for CTE.

How Can CTE be prevented?
Reducing traumatic brain injuries and preventing additional injuries after a concussion can prevent CTE. Helmets can reduce injury for baseball, ice hockey, rugby, skiing and snowboarding, however helmets cannot eliminate the occurrence of concussions, according to the Mayo Clinic.