Efforts to understand the mental health effects of disasters in the U.S. have been hindered because large-scale events have thankfully been sparse. As the one-year anniversary of the terror attacks on the World Trade Center and the Pentagon nears, the nation is still coming to terms with life in a changed world, but scientists are beginning to quantify the psychological damage the terrorism caused. According to a study published today in the Journal of the American Medical Association, New Yorkers who experienced direct exposure to the events of September 11 had higher psychological stress levels following the attacks than other Americans did.

William E. Schlenger of the Research Triangle Park Institute and his colleagues surveyed 2,273 randomly selected adults between one and two months after the attacks. The sample included respondents from seven specific metropolitan areas, including Washington, D.C., and New York City, as well as a group representative of the rest of the country. Subjects were asked questions regarding their exposure to the terrorist attacks, both direct and indirect, and their experience of symptoms indicative of psychological anxiety and post-traumatic stress disorder (PTSD). Because the survey relied on self-reporting instead of a physician's diagnosis, an accurate count of PTSD cases was impossible. Instead, the scientists assessed the likelihood of "probable PTSD." They determined that the prevalence of probable PTSD among people who were in New York City on September 11 was 11.2 percent, compared to 4.3 percent for the nation as a whole. The rate among people in Washington, D.C., the team reports, was not statistically different than the national rate. In addition, the researchers found that the prevalence of probable PTSD was significantly associated with the number of hours of TV coverage of the attacks that participants reported watching, and with the number of different kinds of potentially traumatic events they reported seeing.

The results provide an excellent example of data collected soon after a major disaster, write Carol S. North of Washington University and Betty Pfefferbaum of the University of Oklahoma in an accompanying editorial. But they also caution that the findings cannot tell the whole story. "Although early postdisaster research findings provide a valuable glance at the nation's mental health shortly after the September 11 attacks," they note, "these data do not necessarily predict what might be expected over time."