Official URL: https://doi.org/10.1037/tra0000596

Objective: Distinct models of posttraumatic stress disorder (PTSD) are outlined in the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM–5) and the 11th version of the International Classification of Diseases (ICD-11). Limited data exists about the validity of these models among older adults. This study examines the probable prevalence rates of PTSD in older adults; the factorial validity of both models; and symptom-endorsement bias across sex. Method: Using a nationally representative (United States) sample (n = 5,366) of older adults aged 60 years and older, alternative PTSD factor models were tested using confirmatory factor analysis (CFA), and item bias was assessed using differential item functioning (DIF) analysis. PTSD was measured without the functional impairment criterion, likely resulting in inflated prevalence rates. Results: DSM–5 (9.5%) PTSD prevalence was significantly higher than ICD-11 (8.7%). Women were more likely to meet criteria for DSM–5 (OR = 1.79) and ICD-11 (OR = 1.38) PTSD. CFA results showed that both models of PTSD had excellent fit. Four DSM–5 symptoms demonstrated DIF, with females more likely to endorse three symptoms (B1: “unwanted memories”; B4: “feeling upset”; and E6: “sleep problems”) and males more likely to endorse one symptom (E2: “reckless or self-destructive behavior”). No DIF was present for the 6 ICD-11 symptoms. Conclusion: Both PTSD models perform well among older adults, although there is evidence of DIF in the DSM–5 model. A considerable proportion of older adults met diagnostic requirements for PTSD, thus highlighting the importance of trauma-related research among older adult populations.