Former Miami Dolphins wide receiver Mark Duper revealed to ESPN's "Outside The Lines" that he has been diagnosed with signs of chronic traumatic encephalopathy.
CTE is a degenerative brain disease that scientists believe is caused by head trauma and linked to depression and dementia.
Duper is the ninth known living former NFL player diagnosed with CTE.
"It was shocking," he said. "I hoped nothing was wrong. I've had memory things where I would go to the store and forget what I went for. And I have emotional swings and panic attacks."
Duper is one of four former stars -- the others are Tony Dorsett, Joe DeLamielleure and Leonard Marshall -- who were tested at UCLA over the past three months and diagnosed with signs of CTE. UCLA announced in January that five other former NFL players were tested and diagnosed.
Prior to the recent findings, CTE had only been diagnosed posthumously. Autopsies performed on more than 50 former NFL players -- including Junior Seau, who committed suicide in 2012, and Mike Webster -- found signs indicative of CTE.
ESPN reported Wednesday that Dorsett, DeLamielleure and Marshall each described having memory loss, depression and suicidal thoughts.
"Once upon a time, everybody has thought about suicide, but I am not going to do it," Duper said.
Duper, 54, hopes CTE will receive more public awareness.
"I think this test will show the damage we are doing to our bodies and how to prevent it," he said. "People have to speak up about CTE. I hope me speaking out will show that people should be tested."
There is no known cure for CTE.
Duper played all 11 of his NFL seasons with the Dolphins, which included four 1,000-yard seasons.