Posttraumatic stress disorder associated with combat service in Iraq or Afghanistan: reconciling prevalence differences between studies.

Studies of posttraumatic stress disorder (PTSD) prevalence associated with deployment to Iraq or Afghanistan report wide variability, making interpretation and projection for research and public health purposes difficult. This article placed this literature within a military context. Studies were categorized according to deployment time-frame, screening case definition, and study group (operational infantry units exposed to direct combat versus population samples with a high proportion of support personnel). Precision weighted averages were calculated using a fixed-effects meta-analysis. Using a specific case definition, the weighted postdeployment PTSD prevalence was 5.5% (95% CI, 5.4-5.6) in population samples and 13.2% (12.8-13.7) in operational infantry units. Both population-level and unit-specific studies provided valuable and unique information for public health purposes; understanding the military context is essential for interpreting prevalence studies.