Long-term Posttraumatic Stress Symptoms among 3,271 Civilian Survivors of the September 11, 2001, Terrorist Attacks on the World Trade Center

Laura DiGrande; Yuval Neria; Robert M. Brackbill; Paul Pulliam; Sandro Galea


Am J Epidemiol. 2011;173(3):271-281. 

In This Article

Abstract and Introduction


Although the September 11, 2001, terrorist attacks were the largest human-made disaster in US history, there is little extant research documenting the attacks' consequences among those most directly affected, that is, persons who were in the World Trade Center towers. Data from a cross-sectional survey conducted 2–3 years after the attacks ascertained the prevalence of long-term, disaster-related posttraumatic stress symptoms and probable posttraumatic stress disorder (PTSD) in 3,271 civilians who evacuated World Trade Center towers 1 and 2. Overall, 95.6% of survivors reported at least 1 current posttraumatic stress symptom. The authors estimated the probable rate of PTSD at 15.0% by using the PTSD Checklist. Women and minorities were at an increased risk of PTSD. A strong inverse relation with annual income was observed. Five characteristics of direct exposure to the terrorist attacks independently predicted PTSD: being on a high floor in the towers, initiating evacuation late, being caught in the dust cloud that resulted from the tower collapses, personally witnessing horror, and sustaining an injury. Working for an employer that sustained fatalities also increased risk. Each addition of an experience of direct exposure resulted in a 2-fold increase in the risk of PTSD (odds ratio = 2.09, 95% confidence interval: 1.84, 2.36). Identification of these risk factors may be useful when screening survivors of large-scale terrorist events for long-term psychological sequelae.


Posttraumatic stress disorder (PTSD) is a psychiatric disorder that occurs after experiencing or witnessing events that threaten death or serious injury and that involves intense feelings of fear, helplessness, or horror.[1] National studies have demonstrated that 6.8% of adults develop PTSD in their lifetimes; 3.5% of adults have the condition in any given year, making PTSD the third most common anxiety disorder in the United States.[2,3] Although trauma exposure is a necessary component of PTSD, the presence of a traumatic event by itself does not sufficiently explain why PTSD develops. Substantial variability in the likelihood of developing PTSD after different events exists. For example, the prevalence of PTSD after rape has been estimated to be 55%; in contrast, the prevalence of PTSD after accidents has been estimated to be 7.5%.[4]

Intentional disasters, particularly large-scale terrorist attacks, allow for the study of PTSD in unselected communities and circumvent confounding that can occur in community studies of the association of trauma with vulnerability to psychopathology.[5,6] It has been hypothesized that posttraumatic stress symptoms after such disasters may be long-lasting because of the high prevalence of factors known to contribute to the disaster-psychopathology relation (e.g., direct exposure, the witnessing of horror, experience or knowledge of extensive loss of life, relocation, and postdisaster financial strain).[7]

The magnitude and intensity of the attack on the World Trade Center (WTC) on September 11, 2001 (9/11), made it the worst human-made disaster in the history of the United States, with almost 3,000 fatalities, 71,000 jobs lost, and labor and capital losses reaching $36 billion in the months after the attacks.[8] Previous research documented a high prevalence of posttraumatic stress symptoms in national and New York City samples within 6 weeks of the attacks and attenuation of symptoms 5 months later.[9–13] However, we are unaware of studies devoted exclusively to the psychological consequences among those under direct attack on 9/11: persons who were in the WTC towers. We sought to fill this gap in knowledge by assessing long-term stress reactions among civilians who escaped the WTC towers on the morning of 9/11. Our objectives were to 1) measure the prevalence of posttraumatic stress symptoms and probable PTSD in a large cohort of tower survivors 2–3 years after 9/11; 2) describe the range of direct exposures reported; and 3) assess the independent and collective relations between these exposures and the risk of probable PTSD. Because this study targets those with the greatest exposure, we hypothesized that the burden of posttraumatic stress would be higher than that documented in previous 9/11 studies and that there would be a positive relation between the number of direct exposures reported and the number of cases of posttraumatic stress observed.


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