Lifetime prevalence of posttraumatic stress disorder in two American Indian reservation populations.

Posttraumatic stress disorder (PTSD) has been found to be more common among American Indian populations than among other Americans. A complex diagnosis, the assessment methods for PTSD have varied across epidemiological studies, especially in terms of the trauma criteria. Here, we examined data from the American Indian Service Utilization, Psychiatric Epidemiology, Risk and Protective Factors Project (AI-SUPERPFP) to estimate the lifetime prevalence of PTSD in two culturally distinct American Indian reservation communities, using two formulas for calculating PTSD prevalence. The AI-SUPERPFP was a cross-sectional probability sample survey conducted between 1997 and 2000. Southwest (n = 1,446) and Northern Plains (n = 1,638) tribal members living on or near their reservations, aged 15-57 years at time of interview, were randomly sampled from tribal rolls. PTSD estimates were derived based on both the single worst and 3 worst traumas. Prevalence estimates varied by ascertainment method: single worst trauma (lifetime: 5.9% to 14.8%) versus 3 worst traumas (lifetime, 8.9% to 19.5%). Use of the 3-worst-event approach increased prevalence by 28.3% over the single-event method. PTSD was prevalent in these tribal communities. These results also serve to underscore the need to better understand the implications for PTSD prevalence with the current focus on a single worst event.