In our survey of a representative sample of adults living south of 110th Street in Manhattan, conducted five to eight weeks after the September 11 attacks, 7.5 percent of the respondents reported symptoms consistent with the diagnosis of current PTSD, and 9.7 percent reported symptoms consistent with the diagnosis of current depression. These prevalences suggest that in the area below 110th Street approximately 67,000 persons had PTSD and approximately 87,000 had depression during the time of the study.9 Although the estimated prevalences of current psychopathology vary according to the population studied, in a benchmark national study, the prevalence of PTSD within the previous year was 3.6 percent,10 and the prevalence of depression within the previous 30 days was 4.9 percent,11 suggesting that the prevalences in our survey were approximately twice the base-line values.

The prevalence of psychological sequelae of disasters has been documented in only a few community-based samples, and comparison of the findings is limited by differences in sampling frames and the interval between the event and the assessment. Using outcome measures that were similar to ours, Hanson et al. reported that the overall prevalence of PTSD was 4.1 percent six months after the 1992 civil disturbances in Los Angeles County.12 The prevalence of depression in our study is similar to that reported after floods (9.5 percent).13

Persons directly affected by disasters have higher rates of post-event psychiatric disorders than persons indirectly affected.14,15 Our survey showed that the prevalence of PTSD was higher among the persons who were most directly exposed to the attacks or their consequences (e.g., those living south of Canal Street, the area closest to the attacks, and those who lost possessions) than among persons with less direct exposure. Factors associated with grief (e.g., loss of a family member) increased the likelihood of depression, a finding that is consistent with the results of previous studies.16,17

We found bivariate associations between female sex and both PTSD and depression, a finding that is consistent with the results of most studies.3,16,18 However, our adjusted models suggested that other factors may have been important mediators of the association between sex and psychopathology after this disaster. For example, the level of social support may have influenced the association between sex and depression.

Hispanic ethnicity was associated with both PTSD and depression, and the association was independent of other covariates. Although the relation between membership in a minority group and psychopathology after a disaster has been suggested in previous studies,19 few have specifically examined the role of Hispanic ethnicity.20 Research with veterans of the Vietnam War has shown that Hispanics may have a higher prevalence of PTSD than persons of other racial or ethnic backgrounds.21 Sociocultural influences have been proposed as mediators of this relation.22

We also found a relation between a low level of social support and both PTSD and depression in bivariate analyses and between a low level of social support and depression in adjusted analyses. Social ties have a positive role in mental health.23 After a disaster, a low level of social support has been shown to be related to PTSD and depressive symptoms.24,25

Our study provides strong evidence of an association between initial panic symptoms and subsequent psychopathology. Although the prognostic role of panic symptoms in determining the risk of PTSD or depression cannot be determined from a cross-sectional survey, this finding is consistent with previous research documenting associations between initial emotional responses to trauma and the development of PTSD.26,27 These findings suggest that interventions addressing such initial reactions to a disaster may help prevent the development of long-lasting psychological sequelae.28

Prospective evaluations of PTSD in trauma victims and in the general population suggest that the symptoms of PTSD decrease substantially within three months after a traumatic experience29 but that up to a third of cases of PTSD may not fully remit.3,30 How long the psychological sequelae of the September 11 attacks will last remains to be seen, and it is possible that the prevalence of symptoms in our study reflects transient stress reactions to some degree. However, the ongoing threat of terrorist attacks may affect both the severity and the duration of these psychological symptoms.31 More than 100,000 persons in New York City may lose their jobs as a result of the September 11 attacks,32 and the cleanup efforts and disruption of services throughout the city will continue for a long time. In this context, the high prevalence of psychopathology that we documented among the residents of Manhattan is not surprising. Future research in New York City should determine the prognostic role of the factors that were associated with PTSD and depression in our study.