Trauma and conditional risk of posttraumatic stress disorder in two American Indian reservation communities.

Purpose: To determine conditional risk of posttraumatic stress disorder (PTSD) in two culturally distinct American Indian reservation communities.

Method: Data derived from the American Indian Service Utilization, Psychiatric Epidemiology, Risk and Protective Factors Project, a cross-sectional population-based survey that was completed between 1997 and 2000. This study focused on 1,967 participants meeting the DSM-IV criteria for trauma exposure. Traumas were grouped into interpersonal, non-interpersonal, witnessed, and "trauma to close others" categories. Analyses examined distribution of worst traumas, conditional rates of PTSD following exposure, and distributions of PTSD cases deriving from these events. Bivariate and multivariate logistic regressions estimated associations of lifetime PTSD with trauma type.

Results: Overall, 15.9 % of those exposed to DSM-IV trauma qualified for lifetime PTSD, a rate comparable to similar US studies. Women were more likely to develop PTSD than were men. The majority (60 %) of cases of PTSD among women derived from interpersonal trauma exposure (in particular, sexual and physical abuse); among men, cases were more evenly distributed across trauma categories.

Conclusions: Previous research has demonstrated higher rates of both trauma exposure and PTSD in American Indian samples compared to other Americans. This study shows that conditional rates of PTSD are similar to those reported elsewhere, suggesting that the elevated prevalence of this disorder in American Indian populations is largely due to higher rates of trauma exposure.