By Jonathan Fildes
Science and technology reporter, BBC News, San Francisco
Virtual reality is being used to treat soldiers returning from Iraq with post-traumatic stress disorder.
Patients saw immediate post treatment gains, researchers said
The immersive system combines realistic street scenes, sounds and odours to allow patients to relive traumatic events in a controlled environment.
During the "exposure therapy", a clinician determines the intensity of the events the soldier experiences.
The prototype system is currently being trialled in the US but has already successfully treated four volunteers.
"We see immediate post treatment gains," said Dr Skip Rezzo of the University of Southern California and one of the team that developed the system.
In particular, the system seems to help with symptoms such as nightmares and flashbacks.
"Those are the cold clinical symptoms but this translates into being able to leave the house, being able to go to work or being able to continue your relationship with your wife or loved ones," said Dr Rezzo.
Post traumatic stress disorder (PTSD) is a condition suffered by many who have been on active service with the Armed Forces.
The term is used to describe a range of psychological symptoms people may experience following a traumatic, usually life-threatening, event.
Symptoms can manifest themselves in different ways but can include reliving the trauma through flashbacks or nightmares, increased irritability and self-isolation.
The system attempts to recreate the reality of war
A study in 2004 by researchers at the Walter Reed Army Institute of Research found that nearly one in eight soldiers returning from Iraq and Afghanistan reported some symptom of PTSD.
The disorder is traditionally treated with psychotherapy and medicines such as antidepressants.
The new technique offers a complementary approach.
Psychotherapists already use exposure therapy to treat stress related disorders
This typically involves the patient being asked to imagine a series of increasingly traumatic events.
It is particularly common for treating phobias such as fear of flying or fear of flights.
However, it is difficult to use on people suffering from PTSD.
"The problem with applying it to PTSD is that one of the symptoms is the avoidance of cues and reminders of the trauma of the event," said Dr Rezzo.
"So what we do in virtual reality is put a person in virtual Iraq, but initially at a level where they only experience minimal anxiety."
To recreate scenes the system uses a headset that can show video-game quality images of one of two scenarios: a street scene and a desert.
These are controlled by a clinician, who can introduce different elements into the scenarios, from playing children to unexpected explosions. The time of day and conditions such as sand storms can also be manipulated.
To make it even more realistic, the system pumps in smells such as gunpowder, burning rubber and body odour. Speakers provide the sound, whilst off-the-shelf sub-woofers placed under the chair recreate movements.
Other researchers at Emory University and Cornell University in the US have created similar systems to treat Vietnam veterans and people caught up in the World Trade Centre attacks in 2001.
Using the University of Southern California system, a typical treatment for a soldier who survived an attack on their vehicle may start with them just standing next to an armoured car in the desert.
"Then you raise the level," explained Dr Rezzo.
"You put them in the humvee (military vehicle), then you put them in it and you add the sounds of the engine, then you ask them to drive down a desert road.
"Over the course of the therapy, significant trauma events would be delivered at the hands of the clinician."
Typical treatment involves two one-hour sessions over five weeks.
Dr Rezzo and his team have already treated four people successfully. The first was a 21-year old female in the US military who had witnessed a number of suicide bombing scenes.
Others involved in the initial trial dropped out after one or two sessions.
Despite this, the team have started a larger trial with other soldiers returning from Iraq. The number involved is undisclosed.
However, Dr Rezzo is keen to point out that the trials are still in their infancy and many more follow up studies need to be done.
"I don't want to sell this as a panacea but the results are encouraging," he said.
The research was presented at the American Association for the Advancement of Science (AAAS) annual meeting in San Francisco, US.