Army Col. Michael J. Roy, left, who oversees the exposure therapy at Walter Reed Army Medical Center, conducts a demonstration of a simulator that represents a new form of Post Traumatic Stress Disorder treatment with Army Sgt. Lenearo Ashford, on Sept. 16, 2008, in Washington, D.C. US Dept. of Defense/John J. Kruzel

The fog of war can change men and women for life, with dire consequences. Post-traumatic stress disorder is a wound left behind after all others have been stitched up and healed. But what if soldiers could experience the trauma of the battlefield in a controlled setting before they were deployed -- in an attempt to perform a kind of psychological vaccination?

PTSD has proved to be a more persistent foe than some insurgent groups. One 2011 study estimates that between 4 and 17 percent of U.S. Veterans of the Iraq War suffer from combat-related PTSD. Meanwhile, 2012 has been the worst year for suicides in the military since 2001, with a rate of more than one per day.

USC researcher Albert “Skip” Rizzo and his colleagues have been developing a form of exposure-based therapy that could help both returning veterans already afflicted with PTSD and new recruits about to head out to the front. It's based on the decades-old tradition of exposure-based therapy, in which a therapist walks the patient through the situation that triggered his or her PTSD, but with a twenty-first century twist: virtual reality.

“The traditional form of exposure therapy is done exclusively with guided imagery and discussion of traumatic experiences,” Rizzo says. “It's going on in the hidden world of the imagination. And one of the symptoms of PTSD is avoidance of trauma.”

A virtual battlefield, on the other hand, can be controlled by the therapist to ensure that a patient is actually confronting distressing imagery. And the model that Rizzo and his team use isn't just watching a screen; in addition to computer-generated imagery, they use immersive sound, along with a chair that shakes with vibrations to simulate anything from the vibration of a Humvee to the concussive force of an IED. They even have a machine to reproduce the smells of war -- rotting garbage, diesel fuel, gunpowder and other scents that can call up traumatic memories.

Traditional talk therapy also carries a stigma with it in the military, with some soldiers seeing entering therapy as a sign of weakness.

“This is one of the big problems with treating PTSD. We're trying to make the process of therapy more palatable, and we're trying to do it in a more systematic fashion,” Rizzo says.

Initial clinical trials seem to show that the virtual reality system helps. In one study of 20 active-duty soldiers who went through the treatment for an average of 11 sessions, 16 of the participants no longer met military clinical standards for PTSD after finishing the program -- on average, the participants' scores on an anxiety exam dropped by a third, and their depression scores decreased by nearly half.

While Rizzo and his colleagues acknowledge that these small uncontrolled trials can't be used to make excessive claims, they noted that in addition to clinical improvements, anecdotal evidence from patient reports shows that they saw improvements in their daily life, which persisted at a follow-up session three months after treatment.

Virtual reality-based therapy can help other kinds of patients, too. Doctors have used it to reduce fear in people with certain phobias, to manage stress in cancer patients, to reduce pain during physical therapy, and for wound care for burn patients. Virtual worlds can assist people with eating disorders and help train children and adults with impaired motor function.

But for soldiers, virtual reality therapy could also have a preventative aspect. Rizzo's team is working on a program called STRIVE, which stands for Stress Resilience In Virtual Environments. With this technology, a soldier becomes virtually immersed in missions that will force him or her to confront emotionally challenging experiences: the deaths or injuries of civilian children, the deaths of fellow soldiers, and handling human remains. A virtual “mentor” then appears in the midst of the digital chaos to offer advice on how to cope and process the experience.

“STRIVE provides a digital 'emotional obstacle course' that can be used as a tool for providing more realistic and context-relevant learning of emotional coping strategies under very tightly controlled and scripted simulated conditions,” Rizzo and his colleagues wrote in a 2012 paper in the journal Medicine Meets Virtual Reality.

Many young soldiers may be drawn to virtual therapy because they've grown up playing video games, but being immersed in a distressing battlefield experience is not exactly the same as wasting enemies in "Call of Duty."

“This is fundamentally different from a game where the mission is to blow up stuff and kill,” Rizzo says. “This is about putting people back in certain situations. It's designed to help.”