NFL players who endured at least three concussions are three times more likely to suffer from depression than a player who had none, according to the University of North Carolina's Center for the Study of Retired Athletes.
In a self-report survey of 2,552 retired NFL players over a period of four years, the center demonstrated a sharp increase in risk of depression with three concussions.
Twenty percent of the 595 players who remembered having at least three concussions were clinically diagnosed with depression later in life, compared with 10 percent who recalled one or two concussions. Almost 7 percent of those with no concussions were diagnosed with depression.
Three years ago, the center reported that retired NFL players who had suffered three concussions were five times more at risk for mild cognitive impairment.
To Dr. Julian Bailes, those studies suggest three concussions represent a threshold number.
"It appears that depression, just like MCI [mild cognitive impairment] is a sequelae, or aftereffect, of having multiple concussions while playing football," said Bailes, who heads the department of neurosurgery at West Virginia University's school of medicine and is the third author of the depression study. "So it appears to me there also may be a threshold number."
The study, published yesterday in the journal of the American College of Sports Medicine and first reported by The New York Times, raised anew the debate over the long-term effects of concussions.
The NFL's concussion committee has refuted the cumulative effect of repeated concussions and rejected the findings of the Center for the Study of Retired Athletes.
But Bruce Laird, who played safety for the Baltimore Colts in a 12-year NFL career, said he puts credence into the warnings in the Carolina study.
"I realize I'm no scientist, and I realize the study is in its infancy, but when you look at the likes of Mike Webster and Andre Waters and numerous other players ... then any intelligent person would have to give a sense of credence to those findings."
Webster suffered from mental impairment that resulted from brain trauma and contributed to his death. Earlier this year, a neuropathologist said that multiple concussions likely contributed to the suicide of Waters.
To address these issues, the NFL's concussion committee is embarking on a $2 million study of retired players.
"That's good," Bailes said. "I look forward to their findings. We will support and help them in any way we can. I hope the NFL can do a bigger, better study. They certainly can do a more well-funded study."