Trauma exposure is a precursor to a diagnosis of posttraumatic stress disorder (PTSD). A dearth of empirical evidence exists on the impact of different measurement practices on estimates of trauma exposure and PTSD within representative epidemiological samples. In the present study, we examined differences in reported trauma exposure and rates of PTSD using single, open-ended question versus list-based trauma assessments in a general community sample. Using data from the third wave of the Montreal epidemiological catchment area study (N = 1029), participants were interviewed in person by a lay interviewer about lifetime history of trauma exposure and PTSD. Prevalence rates of trauma exposure and PTSD diagnosis using single, open-ended question and list-based assessment were compared using a within-subject design. A single, open-ended question versus list-based trauma assessment yielded trauma-exposure rates of 61%, 95% CI [57.8, 63.8] and 78%, 95% CI [75.2, 80.3], respectively. Conditional rates of lifetime PTSD decreased from 6.7%, 95% CI [5.8, 9.4] to 6%, 95% CI [4.4, 7.7], respectively. Increases in trauma exposure were more pronounced in women (33.7%) than men (21.5%), as well as in the younger stratum of study participants (15-24 years old; 36.1%). Underestimation of PTSD using a single, open-ended question assessment was minimal, although all missing cases were women. Our results lend support to the importance of using comprehensive assessments of exposure to potentially traumatic events when conducting epidemiological research, especially when reporting conditional rates of PTSD. Previous research may have underestimated the prevalence of trauma exposure, particularly among young women. (PsycINFO Database Record
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