The conditional nature of posttraumatic stress disorder (PTSD) is unusual among the more common psychiatric disorders. By definition, PTSD can only be diagnosed in those exposed to a DSM-qualifying trauma [1].g Traumas include profoundly stressful experiences, such as suffering violence to self or witnessing it in loved ones. Population-based prevalence statistics, then, can be considered the product of two probabilities: first, exposure to a DSM-qualifying trauma and second, development of PTSD given such exposure (conditional risk). While population-based prevalence statistics are critical for understanding overall mental health, investigations of conditional risk and associated demographic correlates help target prevention and treatment efforts more precisely by focusing, for instance, on those traumas most likely to lead to PTSD. Here, we investigated conditional risk for PTSD in two well-defined American Indian samples.
