Football is a dangerous sport, and the risks that come along with smashing into giant grown men on a regular basis are increasingly clear — and worrisome. Last month, Jordan Reed, the tight end for the Washington Redskins, suffered his sixth concussion. The 26-year-old told The New York Times that the string of traumatic brain injuries — for that’s what concussions are — was making him wonder if he should leave the sport he loves for the sake of his health. Why is he so concerned? Well, chances are, this won’t be Reed’s last injury.

“If you’ve had a concussion in the past, it will not take as much force to generate the next concussion,” explains Dr. Viet Nguyen, neurophysiologist at Stanford Health Care who spoke to Inverse on Tuesday. Although researchers don’t know exactly how much the effect “stacks,” it’s clear that each concussion makes it a little bit easier to get the next one.

“People will say ‘oh, well this time he didn’t get hit that hard,’ but that doesn’t matter,” Nguyen says. “The fact is they’ve been hit before, so it won’t take as much force to generate the next concussion.”

The severity of the symptoms — which include memory and concentration problems, irritability, anxiety, and depression — can vary wildly depending on the person and whatever particular hit they took. A sixth concussion doesn’t necessarily feel worse than the first one — but it will probably last longer, and that’s the main concern for Nguyen.

“There are people that have had multiple concussions, and with their first one they’ll say ‘oh I didn’t really have any symptoms other than what I felt that day,’” he explains. But, as players rack up more and more concussions, things get worse, with symptoms lasting weeks or even months.

The dark cloud hovering over football is chronic traumatic encephalopathy (CTE), a degenerative brain disease that’s usually found in athletes with a history of repetitive brain trauma. Nguyen says the line between concussions and CTE isn’t as straight as you might assume. “I think that in the grand scheme of things it is rare to develop CTE with a history of multiple concussions, but it is a possibility, and it is one that we don’t have a cure for at this point,” he says, adding that scientists haven’t yet been able to exactly pin down what makes someone have a higher risk of suffering from the disease.

David Bruton of the Denver Broncos suffered a concussion in 2014.
David Bruton of the Denver Broncos suffered a concussion in 2014.

How concerned, then, should Reed be given his history? “I think there is reason for concern if somebody has had six documented cases of concussions and their recovery periods seem to be getting longer and longer,” Nguyen says of Reed. “When they should leave the sport and if they should leave the sport are valid parts of the discussion that need to happen between Mr. Reed and his physician team.”

It might not be bad news, though. Depending on the methods that Reed’s doctors are treating his concussion with — and how well he responds to that treatment — he could very well continue to play in the NFL. However, Nguyen says Reed likely faces greater odds of getting a seventh concussion when he returns to the field due to his past injuries.

More than anything, though, Nguyen cautions fans and members of the media not to make assumptions. “Care for concussions is very individualized and it’s very hard to determine what people should do if you’re not part of the medical team taking care of them,” he says.

Photos via Getty Images / Doug Pensinger, Getty Images / Jonathan Daniel

James Grebey is a writer, reporter, and fairly decent cartoonist living in Brooklyn. He's written for SPIN Magazine, BuzzFeed, MAD Magazine, and more. He thinks Double Stuf Oreos are bad and he's ready to die on this hill. James is the weeknights editor at Inverse because content doesn't sleep.