On the eve of Veterans' Day, Americans are preparing to honor the 21.8 million men and women who have served in the armed forces: roughly 7 percent of Americans. But nearly 300 of those vets are currently on death row, a number that the Death Penalty Information Center (DPIC) warns is too high, and may be due to ignored post-traumatic stress disorder (PTSD).

In "Battle Scars," a report released Tuesday morning, the DPIC estimates that roughly one in ten death-row inmates has served in the armed forces. The exact number is hard to pin down, thanks to the inconsistency with which courts and agencies record vets' status, and precise figures for PTSD are equally hard to come by.

But between the numerous cases of inmates who have demonstrated symptoms of PTSD, whether diagnosed or not, and statistics that say one million vets from Vietnam, Afghanistan, and Iraq suffer from the disorder, the center says it is high time to bring veterans' trauma into national conversations about mental illness and the death penalty.

"At a time in which the death penalty is being imposed less and less, it is disturbing that so many veterans who were mentally and emotionally scarred while serving their country are now facing execution," Robert Dunham, DPIC's Executive Director, said in a statement.

According to the National Alliance on Mental Illness, PTSD is caused when the body's responses to an emergency situation harm the brain's response system. Symptoms can include flashbacks, hypervigilance, and out-of-body experiences.

The Alliance says 5 percent of men and 10 percent of women will be diagnosed with PTSD at some point in their lifetimes; traumatic events like natural disasters can also prompt it, as Hurricane Katrina did for many New Orleans children.

Societies have long known that damage caused by fighting in wars can be more than physical, even if the modern PTSD diagnosis was not created until 1980 – in part, a response to the experience of Vietnam veterans, who at one point made up 20 percent of the nation's prison population. More than a decade after returning home, 15 percent were still battling PTSD. Nearly half had been jailed, and over one-third arrested multiple times.

According to "Battle Scars," more than 300,000 the most recent vets have PTSD, although only half had received treatment in the year before the study.

"You are unleashing certain things in a human being we don’t allow in civic society, and getting it all back in the box can be difficult for some people,” veteran and prosecutor William C. Gentry told The New York Times for a 2008 story on an uptick in violent crime committed by current or previous soldiers, particularly those with no prior criminal record.

But the war on terrorism, in which enemies aren't always obvious, soldiers are interacting with cultures they've rarely encountered before, and the concept of a 'front line' has largely disappeared, may be especially likely to lead to PTSD, the Times suggested.

As DPIC documents, a fifth of soldiers believed they had killed a civilian, and 12.8 percent considered themselves directly responsible for a child's death — on top of the usual trauma of wartime casualties and carnage.

"PTSD is not an excuse for all criminal acts, but it is a serious mental and emotional disorder that should be a strong mitigating factor against imposing the death penalty,” says Richard Dieter, the DPIC study's author, who alleges that lawyers, judges and juries fail to discuss veteran inmates' mental health. "The mental scars of war can be just as debilitating as physical injuries.”

Mental illness should not be enough to outweigh a heinous crime unless it is "very severe," argued the Criminal Justice Legal Foundation's Kent Scheidigger when interviewed by NBC. Mr. Scheidigger, the Foundation's legal director, pointed out that most PTSD sufferers are not driven to violence.

According to Public Policy Research, Americans from all regions and political affiliations are against executing the mentally ill by a roughly 2-to-1 margin. Yet, an estimated five to 10 percent of death-row inmates suffer from a mental illness, according to the Death Penalty Information Center.

Mr. Dieter believes that mental trauma should at least be discussed in the courtroom – and better treated.

Thanks to stigma and the military's backlog of veterans requesting medical care, many who suffer from PTSD-like symptoms don't receive, or even seek, a diagnosis; some inmates aren't diagnosed until they're in prison.

It may help for the justice system to better document and discuss inmates' veteran status. But other programs have begun focusing on how to help veterans open up about their adjustment back to civilian life, and treat disorders, before it comes to that.

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Increasingly, the Veterans Administration, and smaller veterans' groups, find that vets respond better to peer specialists, who can help them overcome perceived stigma around mental illness to seek the help they need.

"There’s mutual understanding because of our parallel experiences,” as former Air Force sergeant Todd Kuikka told The Christian Science Monitor. Among other vets, he says, "We share things that we won’t share with anybody else – not family, not therapists. It comes down to one simple term: trust."