Five principal limitations need to be noted. First, mental disorders were estimated with screening scales rather than clinical interviews. Despite the fact that the K6 screening scale has been used in national surveys20,29
and has been previously validated19,21,22
and the fact that the modified TSQ was found to be valid in our clinical reappraisal study, screening scales are inevitably less precise than clinical interviews. This imprecision will generate attenuated associations, leading the results reported here on predictors to be conservative. Second, the survey response rate was low and the sampling frame excluded people who were unreachable by telephone, resulting in underrepresentation of the most marginalized and perhaps the most seriously ill people in the population. These sample limitations are likely to make the estimates of disorder and stressor prevalence conservative. Third, even though we interpreted the associations between stressors and disorders in causal terms, it is possible that unmeasured common causes (eg, prehurricane history of psychopathology that influenced both stressor exposure and posthurricane mental illness) influenced the observed associations. Caution is consequently needed in interpreting these associations. Fourth, the assessment of disaster-related stressors was necessarily retrospective, raising concerns about recall bias related to current mental illness. However, this concern is mitigated by evidence from longitudinal studies that reports of acute stress exposure have good test-retest reliability and are relatively free from recall bias.30
In addition, because our assessment was conducted only 5 to 7 months after the hurricane, many of the hurricane-related stressors were still directly and immediately relevant to respondents at the time of their interviews. Fifth, no attempt was made to tease apart the effects of exposure to stressors related to Hurricane Katrina vs Hurricane Rita even though some of the respondents were exposed to Rita in the wake of Katrina. As noted in the section on measures, we asked respondents to include information about stressors related to Rita in their reports. The effects of Rita are consequently included in the results reported here.
Within the context of these limitations, the estimated prevalence of DSM-IV
anxiety and mood disorders in the New Orleans metro was substantially higher than typically found in US population-based surveys of mental illness after natural disasters, while the estimated prevalence in the remainder of the sample was comparable with that in previous studies.9,31
Previous reviews have noted that making comparisons of prevalence estimates across disasters is challenging because of the wide rangeof disaster experiences to which people in disasters are exposed. However, broadly speaking, the high estimated prevalence of anxiety-mood disorders in the New Orleans metro is consistent with the results of studies that considered persons in highly disaster affected areas,1,10
while the lower estimated prevalence in the remainder of the sample is consistent with the results of previous studies in areas with lower disaster impact.3,5
We found that the vast majority of respondents estimated to have SMI (98.1% in the New Orleans metro and 85.8% in the remainder of the sample) also screened positive for PTSD, reinforcing the notion that PTSD is the central form of psychopathology associated with natural disasters.32
Nearly one-fourth of New Orleans metro respondents and one-sixth of other respondents were exposed to traumatic hurricane-related stressors, while the vast majority of respondents (79%-90%) were exposed to other hurricane-related stressors. Comparing these estimates with other postdisaster samples is challenging because few previous studies either attempted to sample complete populations affected by large disasters or comprehensively assessed disaster-related stressors. However, to the extent that comparisons allow, it appears that the proportion of people experiencing hurricane-related stressors after Katrina was substantially higher than after other recent hurricanes, such as Hurricane Andrew in 199333
and Hurricanes Charley/Frances/Ivan/Jeanne in 2004.34
Although the hurricane-related stressors assessed here were significant predictors of estimated anxiety-mood disorders, the stressors with the highest ORs were different in the New Orleans metro (physical illness/injury and physical adversity) than the remainder of the sample (property loss). It is especially striking that the impact of property loss was less in the New Orleans metro than the remainder of the hurricane area even though property loss was much more commonly experienced in the New Orleans metro than the remainder of the hurricane area. One possible explanation for this difference is that personal property loss might have been experienced as less stressful in a situation where, as in the New Orleans metro, property loss was the norm in the population. Or it might be that evacuation and physical displacement, which occurred to the vast majority of prehurricane residents of the New Orleans metro, created a context in which property loss had much less of an emotional effect than in the rest of the hurricane area. It is also possible that the subjective stressfulness of property loss was lessened in the context of the situation in the New Orleans metro, where many people were exposed to even worse stressors, such as death and injury and extreme physical adversity. But these are merely speculations. The only certain conclusion that can be drawn from the results regarding variation in the relative effects of specific stressors in New Orleans and the remainder of the hurricane area is that we have much more to learn about the ways in which multiple exposures and disaster context influence the effects of individual disaster-related stressors.
The findings that women, young people, and people with low socioeconomic status were at comparatively high risk of anxiety-mood disorders are consistent with previously documented correlates of mental illness after disasters9,31
and other traumas.35
Importantly, though, these same associations are found in community epidemiological surveys in the absence of disasters, suggesting that these associations might be related to preexisting mental disorders.14
Consistent with this possibility, these sociodemographic associations were not explained by exposure to hurricane-related stressors. Nor did we find evidence that the associations of hurricane-related stressors with estimated anxiety-mood disorders differ meaningfully in subsamples defined by these sociodemographic factors.
The finding that Hispanic individuals and people of other minorities exclusive of non-Hispanic black had significantly lower estimated prevalence of anxiety-mood disorders than non-Hispanic white individuals is difficult to interpret. Previous research has found elevated prevalence of postdisaster mental illness among Hispanic people,36
although this was largely Puerto Rican and Dominican individuals whereas the prehurricane Hispanic people in the Katrina area were largely Mexican-American. However, caution is needed in interpreting this finding, because the number of respondents in our minority subsample is quite small (35 respondents) and includes Asian as well as Hispanic individuals. Future research will need much larger samples to investigate ethnic differences in disaster response, noting that elevated prevalence among Hispanic people could well vary substantially among Mexican-American people compared with other segments of the Hispanic population.
The results lead to 4 conclusions. First, the stressors considered here appear to have played a critical role in the high prevalence of hurricane-related anxiety-mood disorders. Second, the fact that the associations between hurricane-related stressors and estimated anxiety-mood disorders were stronger in the New Orleans metro than the remainder of the hurricane area suggests that undetermined vulnerability or contextual factors were present in the New Orleans metro that remain understood. Third, the observation that hurricane-related stressor exposure was widespread and comparable across sociodemographic subsamples means that the impact of the hurricane on mental health was widespread rather than concentrated in any one particular segment of the population. This, in turn, suggests that efforts to address the problem of increased mental illness in the wake of the hurricane must address the needs of persons in all segments of society rather than target specific population segments. This may be particularly challenging for prehurricane residents of the New Orleans metro, many of whom are now living throughout the country. Fourth, evidence that avoidable stressors associated with the slow government response to Hurricane Katrina (eg, physical adversity) had important implications for the mental health of people who lived through Katrina argues strongly for the importance of efficient provision of practical and logistical assistance in future disasters, not only on humanitarian grounds, but also as a way to minimize the adverse mental health effects of disasters.