A brain autopsy of former baseball player Ryan Freel showed signs of chronic traumatic encephalitis (CTE), making him the first Major League Baseball player to receive the diagnosis that is more closely associated with the brutal sport of football. Freel committed suicide last December at age 36, a common fate for sufferers of the disease that can lead to dementia and depression.

Researchers at the Boston University Center for the Study of Traumatic Encephalopathy and Sports Legacy Institute found evidence of CTE, which is believed to be caused by frequent and repeated concussions. The recent book and Frontline documentary League of Denial, by ESPN reporters Mark Fainaru-Wada and Steve Fainaru, examined the relationship between the disease and professional football. League of Denial showed the devastating impact of repeated head injuries on former football players as the degenerative disease led to poor health and early deaths.

But while that story dealt almost exclusively with veteran football players (and some boxers and hockey players), Freel's diagnosis shows that the danger of concussions isn't limited to football's realm. “I think this will educate a new group of people who may never have heard of the football findings, the hockey findings,” Chris Nowinski, the co-founder of the Sports Legacy Institute, told the Times-Union. “CTE can be caused by any brain trauma.”

Freel had a history of head injuries on the field, and claimed that he had "nine or 10 concussions" in his eight-year big-league career. In 2006, Freel told the Dayton Daily News that he heard voices in his head, one of whom he named Farney. "He's a little guy who lives in my head who talks to me and I talk to him," Freel said. "Everybody thinks I talk to myself, so I tell 'em I'm talking to Farney." In 2007, Freel took an elbow to the head and was taken off the field in an ambulance to a nearby hospital.

On the same day as Freel's medical report was given to his family last week, baseball's leadership agreed to eliminate the home-plate collision, a source of several such head injuries. Though baseball has fewer collisions and head injuries than hockey, football, or boxing, athletes in most sports must now be more mindful of the dangers concussions can pose.