Psychological Medicine

Original Articles

Prospective risk factors for new-onset post-traumatic stress disorder in National Guard soldiers deployed to Iraq

M. A. Polusnya1a2a3 c1, C. R. Erbesa1a3, M. Murdocha1a2a4, P. A. Arbisia1a3, P. Thurasa1a3 and M. B. Ratha5

a1 Minneapolis VA Health Care System, Minneapolis, MN, USA

a2 Center for Chronic Disease Outcomes Research, Minneapolis, MN, USA

a3 Department of Psychiatry, University of Minnesota Medical School, Minneapolis, MN, USA

a4 Department of Medicine, University of Minnesota Medical School, Minneapolis, MN, USA

a5 Minnesota Army National Guard, St Paul, MN, USA


Background National Guard troops are at increased risk for post-traumatic stress disorder (PTSD); however, little is known about risk and resilience in this population.

Method The Readiness and Resilience in National Guard Soldiers Study is a prospective, longitudinal investigation of 522 Army National Guard troops deployed to Iraq from March 2006 to July 2007. Participants completed measures of PTSD symptoms and potential risk/protective factors 1 month before deployment. Of these, 81% (n=424) completed measures of PTSD, deployment stressor exposure and post-deployment outcomes 2–3 months after returning from Iraq. New onset of probable PTSD ‘diagnosis’ was measured by the PTSD Checklist – Military (PCL-M). Independent predictors of new-onset probable PTSD were identified using hierarchical logistic regression analyses.

Results At baseline prior to deployment, 3.7% had probable PTSD. Among soldiers without PTSD symptoms at baseline, 13.8% reported post-deployment new-onset probable PTSD. Hierarchical logistic regression adjusted for gender, age, race/ethnicity and military rank showed that reporting more stressors prior to deployment predicted new-onset probable PTSD [odds ratio (OR) 2.20] as did feeling less prepared for deployment (OR 0.58). After accounting for pre-deployment factors, new-onset probable PTSD was predicted by exposure to combat (OR 2.19) and to combat's aftermath (OR 1.62). Reporting more stressful life events after deployment (OR 1.96) was associated with increased odds of new-onset probable PTSD, while post-deployment social support (OR 0.31) was a significant protective factor in the etiology of PTSD.

Conclusions Combat exposure may be unavoidable in military service members, but other vulnerability and protective factors also predict PTSD and could be targets for prevention strategies.

(Received February 03 2010)

(Revised September 14 2010)

(Accepted September 17 2010)

(Online publication December 10 2010)


c1 Address for correspondence: M. A. Polusny, Ph.D., Minneapolis VA Health Care System (116A9), One Veterans Drive, Minneapolis, MN 55417, USA. (Email: