Traumatology, Vol 31(2), Jun 2025, 227-236; doi:10.1037/trm0000508
The posttraumatic stress disorder (PTSD) checklist (PCL) is the most commonly used measure of PTSD. Extensive confirmatory factor analytical research has been undertaken with the instrument, resulting in a proliferation of PTSD factor structures. However, these studies have largely ignored the total scale and instead focused on the symptom clusters of PTSD, despite the original authors indicating that a total score provides a measure of PTSD-symptom severity. To further reinforce the importance of the total score, various cut scores have been provided for the total score to indicate diagnostic PTSD status. Through the use of both classical test theory and nonparametric item response theory, this study examined the dimensionality of the posttraumatic stress disorder checklist (PCL-5). Mokken analysis confirmed the unidimensionality of the PCL-5, with the H coefficients for individual items consistently demonstrating that each item contributes to the measurement of the underlying latent variable. Confirmatory factor analysis substantiated this finding, indicating that the bifactor Diagnostic and Statistical Manual of Mental Disorders—fifth edition model provided the best-fit indices for the data. Together with ancillary bifactor indices, these results support the essential unidimensionality of the PCL-5. Through the combined application of Mokken scale analysis and bifactor indices, this study offers robust and compelling evidence supporting the unidimensionality of the scale and strengthens the evidence for its primary measurement of a single PTSD construct. (PsycInfo Database Record (c) 2025 APA, all rights reserved)