After the suicides of Dave Duerson of the Chicago Bears and Junior Seau of the San Diego Chargers, autopsy results revealed these two football players suffered from CTE.
"If we look at how they've been in life, when they're younger, had behavioral and mood and depression issues, and then as they get older in life, they have memory and thinking problems," said Dr. Andrew Russman with Cleveland Clinic Sports Health.
Boston University researchers studied the brains of 36 male football, hockey, wrestling and boxing athletes. They found nearly two-thirds of them had behavior and mood problems as their first symptoms of CTE. Another one-third started with memory problems.
A history of traumatic brain injury alone isn't very helpful since repeated smaller hits may be enough to start the cascade of brain decay.
"Many of the football players, who after death who've had an autopsy where they found this problem of CTE, have not had a history of multiple concussions. They've had a history of many, many hits," said Dr. Neil Martin with the Ronald Reagan UCLA Medical Center.
UCLA researchers have used a new scanning tool to identify the abnormal brain proteins associated with this type of repetitive injury in five retired professional football players who are still living.
Dr. Andrew Russman, who didn't take part in the studies, says the new findings could help future athletes get the care they need before it's too late.
"So we can identify what their future risk is and offer them services, offer them care, rehabilitation that can help them to function better later in life," said Russman.
The complete study on early mood and memory changes associated with CTE can be found in the online issue of "Neurology."