The results published in the New England Journal of Medicine represents the first large-scale study of the mental health of soldiers returning from the Iraq war.
The researchers also studied soldiers returning from Afghanistan and found that 11 percent showed signs of depression, severe anxiety or post-traumatic stress disorder
In general, the Afghanistan troops were less likely to see serious action while overseas.
Just 1 percent of the troops who had been in Afghanistan said they were responsible for the death of a civilian, versus 14 percent of Army soldiers in Iraq and 28 percent of Marines who served in Operation Iraqi Freedom.
Not surprisingly, the researchers discovered a link between the likelihood of post-traumatic stress and combat. The rate of illness was 4.5 percent for soldiers not involved in shooting and jumped to more than four times that level among soldiers involved in more than five firefights.
The study anonymously surveyed members of three Army units and one Marine unit. The surveys were all conducted in 2003, with some 2,500 troops surveyed before leaving for Iraq and about 3,700 soldiers surveyed after returning from Iraq and Afghanistan.
About 9 percent of soldiers heading to Iraq already showed signs of post-traumatic stress disorder (PTSD), severe anxiety or depression. That rate rose to 17 percent among those returning from Army service in Iraq and nearly 16 percent among those who served there in the Marines.
Studies of long-term PTSD among Vietnam War veterans years after their return showed that some 15 percent suffered from the disorder. Between 2 percent and 10 percent of Gulf War veterans suffered from PTSD. The prevalence of the disorder averages around 3 percent to 4 percent in the general population.
Of the soldiers with symptoms of a mental health problem, only 38 percent to 45 percent indicated they were interested in getting professional help and only 23 to 40 percent said they had received such help in the past year.
“Concern about stigma was disproportionately greatest among those most in need of help from mental health services,” the study’s authors said.
Among the reasons cited for not seeking help, 63 percent of those with signs of mental health problems agreed with the statement “my unit leadership might treat me differently” and 65 percent said that they would be seen as weak.