WASHINGTON - A veteran of the wars in Iraq and Afghanistan, former Marine Capt. Timothy Kudo thinks of himself as a killer - and he carries the guilt every day.
"I can't forgive myself," he says. "And the people who can forgive me are dead."
Clinicians suspect some troops are suffering from what they call "moral injuries" - wounds from having done something, or failed to stop something, that violates their moral code.
Though there may be some overlap in symptoms, moral injuries aren't what most people think of as PTSD, the nightmares and flashbacks of terrifying, life-threatening combat events. A moral injury tortures the conscience; symptoms include deep shame, guilt and rage. It's not a medical problem, and it's unclear how to treat it, says retired Col. Elspeth Ritchie, former psychiatry consultant to the Army surgeon general.
The Marines, who prefer to call moral injuries "inner conflict," started a few years ago teaching unit leaders to identify the problem. And the Defense Department has approved funding for a study among Marines at California's Camp Pendleton to test a therapy that doctors hope will ease guilt.
But a solution could be a long time off.
"PTSD is a complex issue," says Navy Cmdr. Leslie Hull-Ryde, a Pentagon spokeswoman.
Killing in war is the issue for some troops who believe they have a moral injury, but Ritchie says it also can come from a range of experiences, such as guarding prisoners or watching Iraqis kill Iraqis as they did during the sectarian violence in 2006-2007.
"You may not have actually done something wrong by the law of war, but by your own humanity you feel that it's wrong," says Ritchie, now chief clinical officer at the District of Columbia's Department of Mental Health.
Kudo's remorse stems in part from the 2010 accidental killing of two Afghan teenagers on a motorcycle. His unit was fighting insurgents when the pair approached from a distance and appeared to be shooting. What Marines mistook for guns were actually "sticks and bindles, like you'd seen in old cartoons with hobos," he says.
"There's no day - whether it's in the shower or whether it's walking down the street ... that I don't think about things that happened over there," says Kudo, now a graduate student at New York University.
"Human beings aren't just turn-on, turn-off switches," Veterans of Foreign Wars spokesman Joe Davis says. "You're raised on 'Thou shalt not kill,' but you do it for self-preservation or for your buddies."
The raw number of people who have moral injuries also isn't known. It's not an official diagnosis for purposes of getting veteran benefits, though it's believed by some doctors that many vets with moral injuries are getting care on a diagnosis of PTSD.