Sex differences in post-traumatic stress symptom expression: an analysis of measurement invariance

Numerous studies have delineated a relationship between female sex and increased rates of posttraumatic stress disorder (PTSD) diagnosis. Some have investigated the role of the factor structure in the diagnostic gap between males and females. However, many of these studies have limitations around obtaining a large, representative sample of adults that can appropriately provide the power necessary to examine possible bias inherent to the item and factor structure. To determine how symptoms and factor structure vary by sex and may contribute to this sex-based diagnostic gap, we systematically reviewed relevant papers that have conducted factor and item analysis to comprehensively target the role of biological sex on factors as well as symptom level differences between females and males. We then conducted factor and item level analysis using responses on the PTSD Checklist – specific type collected from the Detroit Neighborhood Health Study data. Factor analysis showed invariance at the strict factorial level. Differential item functioning (DIF) was found in four items: anhedonia, emotionally numbing, difficulty concentrating, and difficulty sleeping. On these four items, females systematically endorsed higher rates of PTSD severity. However, the effect sizes were small. Overall, this study shows modest sex-based bias operating at the item level that does not translate to the factor level.