April 28, 2003 — Having one or more concussions sometime in your life may boost the risk of later developing depression — at least if you’ve played professional football. And the more the head injures, the higher the risk, suggests new research.

In surveying nearly 2,500 retired professional football players, researchers found clinical depression was twice as likely to occur in those who sustained at least three concussions during their career and was three times as likely in those with at least five, compared with former players without a history of concussions.

The survey indicated that two in three players reported one concussion during their professional career, and one in four had at least three. Those surveyed played nearly seven seasons professionally and at least 70% of those who had concussions returned to play that same game. Statistics show the typical player has two concussions while in the NFL.

While depression often occurs immediately following a concussion, it often improves along with the injury. Yet these findings — presented Monday at the annual meeting of the American Association of Neurological Surgeons — suggest a longer-lasting effect, since the average respondent was 58 years and long retired when the data were collected.

However, researchers at the Center for the Study of Retired Athletes at the University of North Carolina, who conducted the survey, say it’s unclear why repeated concussions appear to raise the risk of later depression.

Up to 20% of the more than 1 million Americans who play organized football — from youth leagues to professional levels — sustain at least one concussion each year, including some 64,000 high school athletes.

Last November, the University of Pittsburgh School of Medicine Sports Medicine Concussion Program reported that concussions among high school football players and other athletes appear to have a cumulative effect, and with each head blow, their brains are more vulnerable to damage from even mild future hits. That study showed athletes were up to nine times more likely to lose consciousness or have amnesia after three concussions compared with those suffering an even harder concussion-causing first injury.

However, the lead researcher of that study tells WebMD it’s too early to suggest that depression can result from repeated concussions based on survey results.

“This finding is certainly an interesting first step in helping to learn more about the long-term effects of concussion, but I don’t think it can be considered conclusive,” says neuropsychologist Micky Collins, PhD, a specialist in concussion injuries. “There are a myriad of factors that can’t be accounted for in any type of survey study.”

For instance, retired football players are more likely to have other pain-causing injuries that could contribute to higher rates of depression — and those who are afflicted with numerous concussions, one might reason, are more likely to endure other types of serious or chronic injuries.

“The medical issues in this population or anyone who played contact sports for years is higher than what you’d find in the general population,” Collins tells WebMD. “And rates of depression are higher in older folks, regardless of whether they’re athletes or not. I’m certainly not discounting these findings, but to better determine the role concussion may later have on depression, what is needed is more longitudinal studies — those that follow the same group of athletes for a long period and take into account other factors that may better explain an association.”