For the first time, the degenerative brain disease C.T.E. has been diagnosed in a female professional athlete, researchers reported.

Heather Anderson, an Australian rules football player who died last year, was found to have had C.T.E., researchers said in a paper published in Acta Neuropathologica.

“As the representation of women in professional contact sports is growing, it seems likely that more C.T.E. cases will be identified in female athletes,” the report said. “Given females’ greater susceptibility to concussion, there is an urgent need to recognize the risks, and to institute strategies and policies to minimize traumatic brain injuries in increasingly popular female contact sports.”

Anderson started playing Australian rules football when she was 5 years old, eventually competing in the top women’s league for the Adelaide Crows. She retired at 23 in 2017 after a shoulder injury. She died by suicide, her family said, at 28. She had one confirmed concussion in her career, and as many as four more suspected by her family but not formally diagnosed.

“It was a surprise, but not a surprise,” her father, Brian, told the Australian Broadcasting Corporation program 7.30 of the diagnosis. “And I think now that this report has been published, I’m sort of trying to think about how it might play out for female sportspeople everywhere.”

C.T.E. can eventually lead to depression, memory loss and changes in personality, including aggressive behavior. It is worsened the longer an athlete competes in contact sports. The condition can only be diagnosed posthumously; Anderson’s family donated her brain to the Australian Sports Brain Bank for research.

Researchers found three lesions on Anderson’s brain. They indicated early stage C.T.E., which would be expected given her young age.

The vast majority of C.T.E. cases have come in men, especially those who participated in contact sports for many years. including the American football players Junior Seau, Ken Stabler, Frank Gifford, Mike Webster and Andre Waters. as well as boxers and Australian football and rugby players. Aaron Hernandez, the N.F.L. player who was convicted of murder in 2015 and who died by suicide at 27, was found to have severe C.T.E. damage like that of a player in his 60s.

The researchers said only a handful of cases had been previously found in women, and none before in a professional athlete.

Contact sports for women, notably rugby, are booming in many regions. A women’s top-flight Australian rules league started in 2017; Anderson played in the league’s first grand final.