Gender differences in posttraumatic stress symptoms among OEF/OIF veterans: an item response theory analysis.

Establishing whether men and women tend to express different symptoms of posttraumatic stress in reaction to trauma is important for both etiological research and the design of assessment instruments. Use of item response theory (IRT) can reveal how symptom reporting varies by gender and help determine if estimates of symptom severity for men and women are equally reliable. We analyzed responses to the PTSD Checklist (PCL) from 2,341 U.S. military veterans (51% female) who completed deployments in support of operations in Afghanistan and Iraq (Operation Enduring Freedom/Operation Iraqi Freedom [OEF/OIF]), and tested for differential item functioning by gender with an IRT-based approach. Among men and women with the same overall posttraumatic stress severity, women tended to report more frequent concentration difficulties and distress from reminders whereas men tended to report more frequent nightmares, emotional numbing, and hypervigilance. These item-level gender differences were small (on average d = 0.05), however, and had little impact on PCL measurement precision or expected total scores. For practical purposes, men's and women's severity estimates had similar reliability. This provides evidence that men and women veterans demonstrate largely similar profiles of posttraumatic stress symptoms following exposure to military-related stressors, and some theoretical perspectives suggest this may hold in other traumatized populations.