In a previous article, we explored the definition of trauma, and reviewed the DSM-V diagnostic criteria for two trauma-related mental health disorders: acute stress disorder (ASD) and posttraumatic stress disorder (PTSD). The answer to how many people in a given population have AST or PTSD is not straightforward, as it should be considered in the context of how many potentially traumatic events (PTEs) people are exposed to in the general community. Countries in prolonged conflict or who are prone to natural disasters (flooding or hurricanes, for example) may have higher exposure rates to potentially traumatic events and thus a higher per-capita ratio of PTSD in the general population than countries with fewer PTEs occurring. The ratio of PTSD-to-PTE may not be higher, however, than countri... »