Its findings show "a significant risk of mental health problems" among soldiers on the front-line, according to researchers led by Charles Hoge at the US Army's Walter Reed Army Institute of Research in Maryland.

Researchers canvassed soldiers in four combat infantry units, three army units and one Marine Corps unit, deployed in Iraq and Afghanistan, including troops of the 82nd Airborne Division and the 3rd Infantry Division.

Anonymous questionaires were filled in by the soldiers before their postings to Iraq and three to four months after returning from duty in Iraq and Afghanistan. The study didn't poll wounded soldiers or those charged with bad conduct.

Researchers found depression, anxiety and stress disorders rose sharply among troops sent to Iraq and Afghanistan, ranging between 11.2 and 17.1 percent, compared with their mental state of mind before deploymentpercent).

The difference was most apparent for PTSD, particularly in Iraq where fighting and almost daily attacks against US forces since the fall of Baghdad has been fiercer.

"There was a strong reported relation between combat experiences, such as being shot at, handling dead bodies, knowing someone who was killed, or killing enemy combatants, and the prevelance of PTSD," the study found.

PTSD increased among soldiers depending on the number of fire fights they had experienced, higher rates of PTSD were found among troops involved in more frequent skirmishes.

The study is in Thursday's New England Journal of Medicine.

WAR.WIRE