The structure of co-occurring PTSD and depression symptoms in a cohort of Marines pre- and post-deployment

Symptoms of posttraumatic stress disorder (PTSD) and major depressive disorder are the most frequently co-occurring problems following potentially traumatic events. It is unclear whether these comorbidities represent two correlated but distinct disorders or a common post-event response. We sought to inform this question by examining the distinctiveness of PTSD and depression symptoms at four cross-sectional time points, using data from a parent prospective longitudinal study of 858 Marines evaluated before deployment and approximately 1, 5, and 8 months after returning from the Afghanistan war. We conducted a series of cross-sectional confirmatory factor analyses of PTSD and depression symptoms at each time point, using the Posttraumatic Stress Disorder Checklist IV and the Beck Depression Inventory II. Analyses indicated that across all four assessments, self-reported symptoms on the measures were best explained by distinct but correlated subclusters of symptoms within each measure. This structure was supported by the data both before and after deployment, even with increases in average PTSD symptoms after deployment. These findings suggest that despite shared method variance and some symptom overlap, self-reports of PTSD and depression symptoms across a stressful combat deployment show distinct symptom subclusters rather than a general common trauma reaction in this sample of Marines.