The Baltimore Sun and ESPN, citing anonymous sources with the Ravens, said his retirement was related to the study.
Urschel, who had spoken about balancing concerns about the safety of the game and his love for it, left before the team’s first full practice of the coming season.
“We respect John and respect his decision,” Coach John Harbaugh said in a statement. “We appreciate his efforts over the past three years and wish him all the best in his future endeavors.”
Urschel became the latest high-profile N.F.L. player to retire after just a few years in the league. A. J. Tarpley, a linebacker on the Buffalo Bills who played at Stanford University, retired last year after sustaining several concussions. The year before, San Francisco 49ers linebacker Chris Borland left the N.F.L. after one season, citing a fear of long-term cognitive damage.
Last week, the Carolina Panthers released Michael Oher, the lineman made famous in “The Blind Side,” the movie that told the story of his growing up with foster parents. Oher, who has been in the N.F.L. concussion protocol since September, was released after failing a physical.
“The Brain is a scary thing,” Oher said on…