The findings are published in the journal Psychological Trauma: Theory, Research, Practice, and Policy.
The study identified three distinct phases of the Iraq War, based on previous reports. The researchers analyzed whether veterans who fought during the insurgency phase — a time in which more guerilla-style tactics were used — were more likely to develop PTSD than those who deployed during the initial invasion phase of the war, or the more recent surge phase.
The study involved 738 men and women who served in Iraq. The researchers found that among the men (about half of the group), the insurgency-phase veterans were more than twice as likely to have a diagnosis of PTSD, compared with those who served in either of the other two phases.
The results remained strong even after the researchers adjusted for a range of other demographic and deployment-related risk factors.
The findings did not apply to the women in the study, although the reasons for this are unclear. Referring to other studies, the researchers say there may be a somewhat different mix of factors that contribute to PTSD in female service members and veterans.
The team, led by Dr. Jonathan Green, is with the Behavioral Science Division of the National Center for PTSD, based at the VA Boston Healthcare System, and with Boston University School of Medicine. In the study, they write that overall the findings suggest that specific enemy combat tactics may be undervalued in understanding what drives PTSD.
“Assessment of the nature of combat may be useful in research and in clinical settings,” the stated.
The researchers also asserted that the comparatively high rates of PTSD among Vietnam War veterans may be explained, at least in part, by taking into account the type of enemy tactics those troops experienced. The researchers compare that war, on the whole, to the insurgency phase of the Iraq conflict.
Prior research aimed at comparing PTSD rates between different wars didn’t allow researchers to control for shifting generational norms and differing social and political climates. Because of this, the researchers chose to focus their analysis only on the Iraq War.
Still, they acknowledge there are other factors not included in the study that could affect PTSD rates, such as the intensity of combat or social or political factors that changed even during the course of the Iraq War.