Nearly 30% of adults exposed to Hurricane Katrina were estimated to have had PTSD at some point after the hurricane. As previously reported,
[19] this estimate is high relative to estimates of PTSD prevalence following other natural disasters in the U.S.
[28] The estimated prevalence of PTSD at baseline was slightly higher and at follow-up slightly lower than in previous reports of the CAG
[2,19] because we excluded the first sub-sample of baseline respondents because of incomplete information on course. Among respondents estimated to have PTSD, approximately 40% had recovered by the time of follow-up. Only about 10% of cases were estimated to have had the disorder for one year or less. This pattern of recovery contrasts with epidemiological evidence on PTSD associated with a wider range of traumas showing that 30-40% of cases recover within the first year.
[7,8] Average duration of estimated PTSD among those who recovered was sixteen-and-a-half months while median duration of estimated PTSD among all cases was more than 27 months. These findings suggest a more persistent course of PTSD associated with Hurricane Katrina than previous US disasters,
[4,29,30] although caution is needed here because prior studies generally defined remission as the absence of full diagnostic at follow-up,
[4,29,30] whereas we defined offset as having no significant PTSD symptoms. Of note, we found high rates of delayed-onset estimated PTSD, which may have resulted from prolonged exposure to traumatic events and stressors following the hurricane, although this possibility remains to be examined in future research.
Of the pre-hurricane characteristics examined here, only family income was associated with course of illness. The finding of a negative association between income and persistence is surprising given that hurricane damage was most pronounced in lower-income areas
[31] and resulted in higher rates of forced migration and stress exposure among individuals with fewer economic resources. Because greater vulnerability to stressful events among low-SES individuals is well-documented,
[32] this finding warrants further investigation in future research. However, such a result is not unprecedented, as some previous research suggests that unexpected traumas might be less able to shatter world views of fairness and safety among low-income compared to middle-income people due to the fact that low-income people are less likely to hold such views in the first place, leading to lower risk of psychopathology after some extreme stressors.
[33,34] Also surprising was the lack of association between pre-hurricane psychopathology and PTSD course, which contradicts prior findings regarding predictors of recovery from PTSD associated with other stressors in community samples.
[13,14]Exposure to hurricane-related stressors was the only other factor associated with recovery. No one with estimated PTSD who experienced a life-threatening event recovered, consistent with evidence that exposure to life-threatening situations during natural disasters is associated with long-term elevations in psychiatric symptoms.
[35] Trauma severity has also been found to predict course of combat-related PTSD
[16] as well as PTSD after Hurricane Katrina in a cross-sectional survey of Mississippi residents.
[6] We also found lower odds of recovery among respondents with hurricane-related difficulties in housing. Housing-related stressors were often ongoing following the hurricane and may be markers of chronic strain associated with repeated relocation and poor quality housing.
Other post-hurricane stressors were unrelated to recovery, with the exception of perceived stress related to physical health problems. Previous studies have shown stress exposure following natural disasters to predict prolonged psychological distress,
[30,36] PTSD onset,
[37,38] and PTSD persistence after Katrina.
[6] Our failure to find such associations should be interpreted with caution because we did not have information about the timing of stressors relative to either onsets or offsets of estimated PTSD and therefore were unable to evaluate temporal sequencing. Other studies have been similarly limited.
[6,30] Although our finding of few predictors of recovery may have been related to relatively better measurement of exposures that occurred during the hurricane than of post-hurricane stressors, these results are broadly consistent with prior research that finds numerous predictors of PTSD onset but few predictors of course.
[16,28]None of the social resources examined was associated with recovery. Prior research found that social support is associated with PTSD recovery among combat veterans,
[15,16,38] and with low distress following natural disasters.
[39,40] Personality characteristics reflecting competence also have been found to protect against PTSD and distress following extreme stressors.
[38,41] The lack of association between these factors and recovery in our study mirrors a number of previous findings in the CAG that factors typically associated with psychopathology following trauma and disaster did not predict mental health after Hurricane Katrina.
[19,42,43] Taken together, these findings suggest that the devastation caused by Hurricane Katrina was so severe and persistent that it overwhelmed the influence of factors that typically promote resilience and recovery.
Study findings should be interpreted in light of several important limitations. First, PTSD was estimated using a screening scale rather than diagnostic interview. Although the TSQ demonstrated excellent psychometric properties in a CAG clinical reappraisal study, screening scales are less precise than clinical interviews, potentially resulting in misclassification. Because misclassification was likely non-differential, it would have resulted in attenuated associations. Second, the CAG response rate was low and the sampling frame excluded individuals who were unreachable by telephone, which likely resulted in under-representation of those with the highest levels of stress exposure and mental illness. This likely resulted in conservative estimates of PTSD prevalence and inflated estimates of recovery. Third, assessment of hurricane-related and post-hurricane stressors was retrospective and subject to recall bias, although available evidence suggests that reports of acute traumatic events are reliable and largely free of recall bias.
[44,45] Assessment of post-hurricane stressors might have been most susceptible to such biases. Findings related to post-hurricane stressors should therefore be interpreted with special caution. Fourth, some individuals estimated to have PTSD may have remitted and relapsed between surveys, which would not have been detected in our assessment. Finally, although the TSQ was only validated as a screen for current PTSD symptoms,
[21] we also used it to estimate PTSD retrospectively during the week when symptoms were the worst. It is unknown whether the psychometric properties of such a retrospective assessment are equivalent to those associated with screening for current symptoms.
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