Cumulative trauma and posttraumatic stress disorder among children exposed to the 9/11 World Trade Center attack.

Two and one-half years after the September 11, 2001 World Trade Center attack, 204 middle school students in an immigrant community located near Ground Zero were assessed for posttraumatic stress disorder (PTSD) symptoms as influenced by "dose" of exposure to the attack and accumulated lifetime traumas. Ninety percent of students reported at least one traumatic event other than 9/11 (e.g., community violence) with an average of 4 lifetime events reported. An interaction was obtained such that the dose-response effect depended on presence of other traumas. Among students with the lowest number of additional traumas, the usual dose-response pattern of increasing PTSD symptoms with increasing 9/11 exposure was observed; among those with medium to high cumulative life trauma, PTSD symptoms were substantially higher and uniformly so regardless of 9/11 exposure dose. Results suggest that traumas that precede or follow mass violence often have as much as if not greater impact on long-term symptom severity than high-dose exposure to the event. Implications regarding the presence of continuing or previous trauma exposure for postdisaster and early intervention policies are discussed.