Julius Thomas is retiring from the NFL at the age of 30 to pursue a Ph.D. in psychology. 

Thomas said he will focus his doctorate on "investigating the effects of contact sports on brain trauma and neurobehavioral performance." He will also participate in research to "identify early warning signs of brain disease."

He said he felt particularly called to the study of CTE: "I knew I wanted to help and knew that this would be a great way to help football players, to be that person who could help them understand what we all are at risk of. I felt inside that this was stuff I needed to understand."

Thomas is a two-time Pro Bowler.