The concussive effects of a single blast from one of the roadside bombs common in the Iraq and Afghanistan wars is enough to cause the same brain injury linked to a recent rash of suicides in professional and amateur football players, according to a new study.

Investigators from Boston University and the Department of Veterans Affairs found chronic traumatic encephalopathy, or CTE, a serious brain injury associated with the repeated blows to the head sustained by football players, boxers, and hockey players, in four deceased veterans exposed to such blasts.

Ann McKee, director of neuropathology service for the VA New England Healthcare System, says the brain damage sustained from blast exposure in those four soldiers was "virtually indistinguishable" from that in athletes who sustained multiple concussions.

The researchers were then able to prove in mice tests that just a single exposure was enough to cause the brain damage, which can only be diagnosed postmortem.

Improvised explosive devices, or IEDs, have been estimated to have caused about two thirds of the more than 6,000 soldier deaths in the Iraq and Afghanistan wars, and to have injured a significant number of the more than 45,000 wounded. The Boston University report suggests that soldiers who weren't immediately wounded from an IED may still have suffered brain damage.

According to Lee Goldstein, lead researcher and author of the study, an IED fashioned from a 120mm artillery round creates blast winds of up to 330 mph, nearly 100 mph faster than the highest natural wind speed ever recorded. Goldstein believes these winds reverberate and cause a whiplash "bobblehead effect" on soldiers.

"The head is being whipped about very quickly over a short period of time—it's not exactly equivalent, but you could say it's like having multiple hits occurring in a short period of time," Goldstein says. "One happens on the ballfield, one happens on the battlefield, but the physics are strikingly similar."

Unless new equipment can keep soldiers' heads stable while experiencing these blast winds, there's little that can be done to prevent the whiplash effect, and most, if not all, soldiers would be equally vulnerable.

Most strikingly, all of the mice who were exposed to lab blasts seemed to experience the same brain damage, which means all soldiers who have been exposed to a blast may be at risk of developing the disease, which causes irritability, memory and attention-span problems, and can lead, in later stages, to dementia and suicidal thoughts.

"There's nothing special about a mouse here. This is physics in action," he says. "The pathology was robustly uniform, strikingly so."

Like many soldiers exposed to IEDs, all of the mice survived the blast winds, but within a month, they were experiencing neurological deficiencies.

"None of the animals perished. They survived, they gained weight, they looked fine," Goldstein says. "But they were quite impaired. They had deficits that correspond to some of the deficits we see in humans."

McKee says that besides blast winds, soldiers are exposed to a host of other possible head injuries, not to mention any previous head injuries they have sustained prior to war.

"Often, soldiers are thrown against a wall or out of a vehicle. It's hard to dissect what's a pure blast-injury," she says.

Researchers have long known that many soldiers experience head injuries and multiple concussions in battle—some believe as many at 20 percent of soldiers may have had a traumatic brain injury, which causes dizziness, lightheadedness, mood changes, and, in severe cases, convulsions, seizures, and nausea.

"What we've gotten very good at is keeping soldiers alive, helping them survive combat. But they're coming back with very important invisible injuries," says William Milberg, associate professor of psychology at Harvard Medical School.

Secretary of Veterans Affairs Eric Shinseki said in a statement that this discovery will hopefully "improve patient care and Veterans' quality of life."

That may be tough in the short term because, so far, CTE can be diagnosed only after death—it appears to be the reason Pro Bowl football players Dave Duerson and Junior Seau shot themselves in the chest, so their brains could be studied by researchers—and so far, the damage appears irreversible. Goldstein says that future studies will be focused on preventing blast damage and potentially reducing brain swelling in the immediate aftermath of a blast.

"If we understand the mechanism, we can start to intervene at every stage," he says.

Milberg and his colleague, Regina McGlinchey, say that the Departments of Defense and Veterans Affairs are increasingly studying brain damage, but many researchers—and injured soldiers—are in uncharted waters. Soldiers have undergone conditions that are psychological traumatic that athletes may have not, McGlinchey says.

"People are treating the PTSD aspects only or the [brain damage] aspects separately," she says. "But to look at it separately gives you an incomplete picture of what's happening. These blast exposures that are so common are both physically and psychologically traumatic."