John Urschel, a Baltimore Ravens’ offensive lineman and PhD candidate in applied mathematics at MIT, has announced his retirement from football at the age of 26. The announcement comes just days after publication of a case study that found widespread signs of a degenerative brain disease among football players who donated their brains to research.

"This morning John Urschel informed me of his decision to retire from football," Ravens’ coach John Harbaugh said in a statement. "We respect John and respect his decision. We appreciate his efforts over the past three years and wish him all the best in his future endeavors."

Urschel played with the Ravens for three seasons and was competing for the starting center job. Thus far, he has not publicly discussed his reasoning for the early and abrupt retirement, which was announced just before the first full-team practice. However, a team source told ESPN that his decision was linked to the new brain study.

The study, published in the Journal of the American Medical Association, found widespread signs of the degenerative brain disease Chronic traumatic encephalopathy (CTE) among the donated brains of 202 former football players. In particular, 99 percent—110 of 111—of brains from former National Football League players had signs of the disease, and many had severe cases. CTE is diagnosed by postmortem examination of brain tissue, but it manifests in life as explosive aggression, progressive memory problems, depression, and dementia.

CTE is thought to be caused by repeated concussive and sub-concussive blows to the head. Its prevalence among football players and disease progression are not yet known, however.

ESPN notes that in January, Urschel told HBO's Real Sports With Bryant Gumbel that his passion for playing football outweighed his concern for head trauma or developing CTE. That’s despite an August 2015 concussion during play that knocked him unconscious and out of the game for a short period.

"I think it hurt my ability to think well mathematically," Urschel said. "It took me about three weeks before I was football-ready. It took me a little bit longer before my high-level visualizations ability came back."

At MIT, he’s already working on nine mathematics research papers published or in process. The Washington Post notes that Urschel's specialties include discrete Schrödinger operators, high dimensional data compression, algebraic multigrid, and Voronoi diagrams. Post retirement, Urschel plans to continue pursuing his doctorate and math career.

Urschel is yet another young football player to bow out of the game early, ESPN notes, suggesting a possible trend in light of concern for long-term health. The Post notes that on Tuesday, New England Patriots’ wide receiver Andrew Hawkins decided to end his career at 31. He also pledged to donate his brain to CTE research.