Since the former National Football League player Andre Waters killed himself in November, an explanation for his suicide has remained a mystery. But after examining remains of Mr. Waters's brain, a neuropathologist in Pittsburgh is claiming that Mr. Waters had sustained brain damage from playing football and he says that led to his depression and ultimate death.
The neuropathologist, Dr. Bennet Omalu of the University of Pittsburgh, a leading expert in forensic pathology, determined that Mr. Waters's brain tissue had degenerated into that of an 85-year-old man with similar characteristics as those of early-stage Alzheimer's victims. Dr. Omalu said he believed that the damage was either caused or drastically expedited by successive concussions Mr. Waters, 44, had sustained playing football.
In a telephone interview, Dr. Omalu said that brain trauma ''is the significant contributory factor'' to Mr. Waters's brain damage, ''no matter how you look at it, distort it, bend it. It's the significant forensic factor given the global scenario.''
He added that although he planned further investigation, the depression that family members recalled Mr. Waters exhibiting in his final years was almost certainly exacerbated, if not caused, by the state of his brain -- and that if he had lived, within 10 or 15 years ''Andre Waters would have been fully incapacitated.''
Dr. Omalu's claims of Mr. Waters's brain deterioration -- which have not been corroborated or reviewed -- add to the mounting scientific debate over whether victims of multiple concussions, and specifically longtime N.F.L. players who may or may not know their full history of brain trauma, are at heightened risk of depression, dementia and suicide as early as midlife.
The N.F.L. declined to comment on Mr. Waters's case specifically. A member of the league's mild traumatic brain injury committee, Dr. Andrew Tucker, said that the N.F.L. was beginning a study of retired players later this year to examine the more general issue of football concussions and subsequent depression.
''The picture is not really complete until we have the opportunity to look at the same group of people over time,'' said Dr. Tucker, also team physician of the Baltimore Ravens.
The Waters discovery began solely on the hunch of Chris Nowinski, a former Harvard football player and professional wrestler whose repeated concussions ended his career, left him with severe migraines and depression, and compelled him to expose the effects of contact-sport brain trauma. After hearing of the suicide, Mr. Nowinski phoned Mr. Waters's sister Sandra Pinkney with a ghoulish request: to borrow the remains of her brother's brain.
The condition that Mr. Nowinski suspected might be found in Mr. Waters's brain cannot be revealed by a scan of a living person; brain tissue must be examined under a microscope. ''You don't usually get brains to examine of 44-year-old ex-football players who likely had depression and who have committed suicide,'' Mr. Nowinski said. ''It's extremely rare.''
As Ms. Pinkney listened to Mr. Nowinski explain his rationale, she realized that the request was less creepy than credible. Her family wondered why Mr. Waters, a hard-hitting N.F.L. safety from 1984 to 1995 known as a generally gregarious and giving man, spiraled down to the point of killing himself.
Ms. Pinkney signed the release forms in mid-December, allowing Mr. Nowinski to have four pieces of Mr. Waters's brain shipped overnight in formaldehyde from the Hillsborough County, Fla., medical examiner's office to Dr. Omalu in Pittsburgh for examination.
He chose Dr. Omalu both for his expertise in the field of neuropathology and for his rare experience in the football industry. Because he was coincidentally situated in Pittsburgh, he had examined the brains of two former Pittsburgh Steelers players who were discovered to have had postconcussive brain dysfunction: Mike Webster, who became homeless and cognitively impaired before dying of heart failure in 2002; and Terry Long, who committed suicide in 2005.
