RESEARCH
Mental illness and suicidality after Hurricane Katrina
Troubles mentaux et tendances suicidaires après le passage du cyclone Katrina
Enfermedades mentales y tendencias suicidas tras el huracán Katrina
Ronald C. KesslerI,1; Sandro GaleaII; Russell T. JonesIII; Holly A. ParkerIV on behalf of the Hurricane Katrina Community Advisory Group
IDepartment of Health Care Policy, Harvard Medical School, 180 Longwood Avenue, Boston, MA 02115, USA
IIDepartment of Epidemiology, University of Michigan School of Public Health, Ann Arbor, MI, USA
IIIDepartment of Psychology, Virginia Tech University, Blacksburg, VA, USA
IVDepartment of Psychology, Harvard University, Boston, MA, USA
ABSTRACT
OBJECTIVE: To estimate the impact of Hurricane Katrina on mental illness and suicidality by comparing results of a post-Katrina survey with those of an earlier survey.
METHODS: The National Comorbidity Survey-Replication, conducted between February 2001 and February 2003, interviewed 826 adults in the Census Divisions later affected by Hurricane Katrina. The post-Katrina survey interviewed a new sample of 1043 adults who lived in the same area before the hurricane. Identical questions were asked about mental illness and suicidality. The post-Katrina survey also assessed several dimensions of personal growth that resulted from the trauma (for example, increased closeness to a loved one, increased religiosity). Outcome measures used were the K6 screening scale of serious mental illness and mild-moderate mental illness and questions about suicidal ideation, plans and attempts.
FINDINGS: Respondents to the post-Katrina survey had a significantly higher estimated prevalence of serious mental illness than respondents to the earlier survey (11.3% after Katrina versus 6.1% before; c²1= 10.9; P < 0.001) and mild-moderate mental illness (19.9% after Katrina versus 9.7% before; c²1 = 22.5; P < 0.001). Among respondents estimated to have mental illness, though, the prevalence of suicidal ideation and plans was significantly lower in the post-Katrina survey (suicidal ideation 0.7% after Katrina versus 8.4% before; c²1 = 13.1; P < 0.001; plans for suicide 0.4% after Katrina versus 3.6% before; c²1 = 6.0; P = 0.014). This lower conditional prevalence of suicidality was strongly related to two dimensions of personal growth after the trauma (faith in one's own ability to rebuild one's life, and realization of inner strength), without which between-survey differences in suicidality were insignificant.
CONCLUSION: Despite the estimated prevalence of mental illness doubling after Hurricane Katrina, the prevalence of suicidality was unexpectedly low. The role of post-traumatic personal growth in ameliorating the effects of trauma-related mental illness on suicidality warrants further investigation.
RÉSUMÉ
OBJECTIF: Estimer l'impact du cyclone Katrina sur la santé mentale et les tendances suicidaires par comparaison des résultats d'une enquête postérieure au passage de ce cyclone avec ceux d'une enquête réalisée auparavant.
MÉTHODES: Dans le cadre de l'enquête National Comorbidity-Survey Replication, réalisée de février 2001 à février 2003, les enquêteurs ont interrogé 826 adultes vivant dans les divisions de recensement ultérieurement touchées par le cyclone. Dans l'enquête effectuée après le passage de Katrina, des entretiens ont été menés avec 1043 adultes constituant un nouvel échantillon de personnes vivant dans la même zone avant le désastre. Ces entretiens comprenaient des questions identiques au sujet des troubles mentaux et des tendances suicidaires. L'enquête post-Katrina a aussi permis d'évaluer plusieurs évolutions de la personnalité consécutives au traumatisme lié au cyclone (rapprochement avec une personne aimée, religiosité accrue, par exemple). L'échelle d'évaluation du degré de souffrance morale K6, permettant de détecter les maladies mentales graves et les troubles mentaux légers à modérés, ainsi que des questionnaires portant sur les idées, les projets et les tentatives de suicide, ont servi à mesurer les résultats.
RÉSULTATS: Chez les personnes interrogées dans le cadre de l'enquête post-Katrina, la prévalence des troubles mentaux graves a été estimée à une valeur nettement plus élevée que chez les personnes interrogées dans l'enquête antérieure (11,3 % après Katrina contre 6,1 % avant le passage du cyclone; c²1 = 10,9 ; p < 0,001), tout comme celle des troubles mentaux légers à modérés (19,9 % après Katrina contre 9,7 % avant le passage du cyclone; c²1 = 22,5 ; p < 0,001). Néanmoins parmi les personnes évaluées comme atteintes d'un trouble mental, la prévalence des idées et des projets suicidaires s'est révélée notablement plus faible dans l'enquête post-Katrina que dans l'enquête antérieure (prévalence des idées suicidaires : 0,7 % après le passage de Katrina contre 8,4 % auparavant, c²1 = 13,1 ; p < 0,001 ; prévalence des projets de suicide : 0,4 % après Katrina contre 3,6 % auparavant ; c²1 = 6,0 ; p < 0,014). Une forte corrélation a été relevée entre cette baisse conjoncturelle de la prévalence des tendances suicidaires et deux facettes du développement personnel après le traumatisme (la foi en sa propre capacité à reconstruire sa vie et la prise de conscience de sa force interne), les différences relatives aux tendances suicidaires étant non significatives entre les deux enquêtes si l'on fait abstraction de l'influence de ces deux paramètres.
CONCLUSION: Bien que la prévalence estimée des troubles mentaux ait doublé après le passage du cyclone Katrina, celle des tendances suicidaires s'est avérée étonnamment faible. Le rôle du développement personnel post-traumatique dans l'amélioration de l'impact des troubles mentaux d'origine traumatique en termes de tendances suicidaires mérite une étude plus approfondie.
RESUMEN
OBJETIVO: Estimar el impacto del huracán Katrina en las enfermedades mentales y las tendencias suicidas comparando los resultados de dos encuestas realizadas antes y después del huracán.
MÉTODOS: En el marco del National Comorbidity Survey-Replication, realizado entre febrero de 2001 y febrero de 2003, se entrevistó a 826 adultos de las Divisiones del Censo que luego se verían afectadas por el Katrina. En la encuesta realizada tras el huracán se entrevistó a una nueva muestra de 1043 adultos que vivían en la misma zona afectada. Se formularon las mismas preguntas sobre las enfermedades mentales y las tendencias suicidas. En la encuesta realizada tras el Katrina se evaluaron también varias dimensiones del desarrollo personal relacionadas con el trauma sufrido (por ejemplo una relación más estrecha con un ser querido, o una mayor religiosidad). Los indicadores de resultados empleados fueron la escala de cribado K6 de enfermedades mentales graves y enfermedades mentales leves/moderadas y diversas preguntas sobre los pensamientos, planes e intentos de suicidio.
RESULTADOS: Entre las personas encuestadas tras el paso del Katrina se observó una prevalencia estimada significativamente mayor de enfermedades mentales graves (11,3% después del Katrina, frente a 6,1% antes de la catástrofe, c²1 = 10,9; P < 0,001) y enfermedades mentales leves/moderadas (19,9% después del huracán, frente al 9,7% anterior; c²1 = 22,5; P < 0,001). Entre los encuestados que se estimó que tenían enfermedades mentales, sin embargo, la prevalencia de ideas y planes suicidas fue significativamente menor en la encuesta realizada tras el Katrina (pensamientos suicidas: 0,7% después, frente a 8,4% antes; c²1 = 13,1; P < 0,001; planes de suicidio: 0,4% después, frente a 3,6% antes; c²1 = 6,0; P = 0,014). Esta menor prevalencia condicional de las tendencias suicidas estaba fuertemente relacionada con dos dimensiones del desarrollo personal tras el trauma: la confianza en la propia capacidad para reconstruir la vida, y una sensación de fortaleza interior; sin dichos factores las diferencias entre las dos encuestas serían desdeñables.
CONCLUSIÓN: Aunque la prevalencia estimada de enfermedades mentales se duplicó tras el huracán Katrina, la prevalencia de tendencias suicidas fue inesperadamente baja. La contribución del desarrollo personal postraumático a la mejora de los efectos de las enfermedades mentales relacionadas con el trauma en las tendencias suicidas debería ser objeto de nuevas investigaciones.
Introduction
Hurricane Katrina was the deadliest hurricane in the United States in seven decades and the most expensive natural disaster in American history. More than 500 000 people were evacuated. Nearly 90 000 square miles were declared a disaster area (roughly equal to the land mass of the United Kingdom).1 More than 1600 confirmed deaths occurred and more than 1000 people remain missing.2 The destruction caused by Hurricane Katrina has lingered much longer than that occurring after previous hurricanes.3
An extensive literature documents the adverse mental health effects of natural disasters.4,5 Although these effects vary greatly, the effects of catastrophic disasters are consistently large.6,7 For example, studies after Hurricane Andrew, which occurred in Louisiana in 1992, found that 25-50% of respondents were affected by disaster-related mental disorders.8,9 Based on these results, and given the extraordinary array of stressors that occurred in conjunction with Hurricane Katrina (for example, bereavement, exposure to the dead and dying, personal threats to life, and the massive destruction),10-12 we would expect Hurricane Katrina's effects on mental health to be at the upper end of the range of previous disasters.
Due to the wide geographical dispersion of the displaced population, a comprehensive assessment of the mental health of survivors of Hurricane Katrina is nonexistent. The Louisiana Department of Public Health documented substantial psychopathology among the 50 000 survivors cared for in evacuation centres shortly after the hurricane,13 but these individuals represented less than 1% of survivors. Seven weeks after the hurricane, the United States Centers for Disease Control and Prevention (CDC) carried out a survey to assess household needs and found that half of the adults surveyed who were still living in New Orleans had clinically significant psychological distress;14 no information was obtained on the much larger number of residents who had lived in New Orleans before the hurricane but who no longer live there. Two public opinion polls one carried out jointly by Gallup, CNN and USA Today in a sample of people who sought assistance from the American Red Cross15 and the other carried out by the New York Times among a sample from the American Red Cross' "safe list" (a list posted on the Internet with the names and contact information of survivors who were displaced by the hurricane and separated from relatives and friends )16 asked a handful of questions about mental health but did not attempt to assess clinical significance. A probability survey of families with children still residing in trailers (caravans) supplied by the United States Federal Emergency Management Agency (FEMA) or hotel rooms sponsored by FEMA in Louisiana as of mid-February 2006 found that 44% of adult caregivers had clinically significant psychological distress.17 As with the earlier CDC survey of evacuation centres, though, the sampling frame represented less than 1% of the pre-hurricane residents of the affected areas.
Public health decisions cannot be based on such a narrow empirical foundation. This report presents the initial results of an ongoing tracking survey designed to provide broader coverage of the population affected by Hurricane Katrina. The first phase of the study aimed to enrol and carry out a baseline survey of mental health needs among a representative sample of adults (aged > 18) who, before the hurricane, were resident in the FEMA-defined impact areas in Alabama, Louisiana and Mississippi.18-20 Subsequent phases of the study will monitor the evolving needs of this sample in follow-up surveys. The focus of this report is on the effects of the hurricane on the prevalence and correlates of mental illness and suicidality. Before and after comparisons are approximated by using baseline data from a 2001-03 national survey that included a probability sub-sample of respondents in the two Census Divisions subsequently affected by Katrina.21 The questions used to assess mental illness and suicidality were identical in the two surveys.
Methods
The samples
The baseline survey was the National Comorbidity Survey-Replication (NCS-R),21 a face-to-face survey of English-speaking adults aged > 18 administered between February 2001and February 2003. The NCS-R interviewed 826 people in the two Census Divisions later affected by Hurricane Katrina. The response rate in the total sample (n = 9282) was 70.9% but a response rate was not calculated separately for the subsample of respondents interviewed in the two Census Divisions subsequently affected by Hurricane Katrina. The NCS-R data were weighted to adjust for differential probabilities of selection and for residual discrepancies between the sample and the 2000 Census on a series of social, demographic and geographical variables. The NCS-R design is discussed in more detail elsewhere.22
The post-Katrina survey acted as the baseline data collection for the Hurricane Katrina Community Advisory Group. The advisory group is a representative sample of 1043 survivors of Hurricane Katrina who agreed to participate in a series of surveys over a period of several years; these surveys will track the speed and effectiveness of hurricane recovery efforts. The target population for the advisory group was English-speaking adults (aged > 18) who before the hurricane had lived in the areas subsequently defined by FEMA as having been affected by Hurricane Katrina (a total of 4 137 000 adult residents in the 2000 Census spread across parts of Alabama, Louisiana and Mississippi) in either of two sampling frames: a random-digit dial telephone frame that included telephone banks working in the eligible counties (in Alabama and Mississippi) and parishes (in Louisiana) in the affected areas before the hurricane and a frame that included the telephone numbers of the roughly 1.4 million families from these same areas who had applied to the American Red Cross for assistance after the hurricane. Pre-hurricane residents of the New Orleans metropolitan area were over-sampled in both frames. Many displaced people were traced in the random-digit dial sample because telephone calls were forwarded to new addresses. The American Red Cross sample also included cell phones (mobile phones). The small proportion of evacuees still living in hotels at the time of the survey was represented through a supplemental sample of hotels that housed evacuees supported by FEMA.
The overlap of the two sampling frames was handled in two ways: by confining numbers from the American Red Cross frame to those not in the random-digit dial frame (for example, cell phones and exchanges outside the hurricane area) and by down-weighting those respondents selected by the random-digit dial frame who reported receiving assistance from the American Red Cross and had additional phone numbers outside the random-digit dial frame. Respondents from the two frames were combined by weighting the participating households in the American Red Cross sample to their estimated population proportion based on estimates of the proportion of Red Cross numbers outside the random-digit dial frame and the proportion of random-digit dial respondents who asked for assistance from the American Red Cross. Respondents in the hotel sample were included without a household weight because they were selected proportionally.
The final sample of 1043 advisory group members was recruited from an initial sample that we estimate to have included 3835 eligible households living in the area before the hurricane and selected across the two frames. We were able to contact and determine to be eligible 2489 of these households. The estimate of 3835 eligible households in the sample is nothing more than an estimate because we were unable to contact a large proportion of this number even after many attempts, leading us to subsample hard-to-reach cases for especially intensive tracing efforts and to estimate rather than to confirm the proportion of eligible households. If the estimate of 3835 is correct, the 2489 households that we contacted and determined to be eligible represent a 64.9% screening response rate. This response rate is lower than that found in typical household surveys because of the geographical dislocation of the population after Hurricane Katrina and the attendant difficulties in tracing and contacting people in this population. For example, some of the phone numbers in the American Red Cross frame were for rooms in hotels where a family was living temporarily at the time they sought assistance. We were able to trace some of these households when they left forwarding information, but often it was not possible to trace households, and this led to a low screening response rate.
A short screening questionnaire was administered to a randomly selected respondent in each of the households contacted for the screening sample; this questionnaire was used to determine eligibility for the advisory group. It included questions about the location of the respondent's residence before the hurricane, the extent of the respondent's exposure to the hurricane, the respondent's current mental health status and basic demographic information. Once these screening questions were answered, respondents who were determined to be eligible to participate by virtue of the location of their residence before the hurricane were introduced to the purposes and goals of the advisory group. They were also informed that agreeing to join the advisory group required making a commitment to participate in a number of follow-up surveys over a period of several years and providing information that would allow us to contact them if they moved house during the study period. We asked respondents to consider these requirements carefully before agreeing to participate because we wanted the advisory group to include only those respondents who would continue to participate in the repeated tracking surveys.
The baseline advisory group survey was administered to the 1043 respondents who agreed to join the group: the results of the survey are presented in this report. These respondents represent 41.9% (1043/2489) of those who participated in the screening questionnaire survey. Although this is a relatively low response rate in comparison to typical one-shot telephone surveys, it is considerably higher than the response rates obtained in more conventional consumer panel surveys. It is noteworthy that responses to the screening questionnaire were quite similar among those who agreed to join the advisory group and those who declined. A weight was nonetheless applied to the advisory group sample. This was done to adjust for observed differences between advisory group participants and non-participants in responses made to the screening questionnaire: there was a somewhat higher level of trauma exposure and a somewhat higher prevalence of hurricane-related psychological distress among non-participants. In addition, a within-household probability-of-selection weight was applied to the advisory group sample to adjust for the fact that in each eligible household only one member was invited to join the advisory group. In addition, a post-stratification weight was applied to the data to adjust for residual discrepancies between the advisory group and the 2000 Census population in the affected areas on a range of social, demographic and pre-hurricane housing variables. Finally, the consolidated advisory group sample weight was trimmed to increase design efficiency based on evidence that trimming did not significantly affect prevalence estimates of outcome variables.
Measures
The K6 scale of non-specific psychological distress23,24 was used to screen for anxiety and mood disorders occurring within 30 days of the interview as defined by the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV). The K6 is the most widely used mental health screening scale in the United States.25,26 Scores on the scale range from 0 to 24. Based on previous K6 validation,24 scores in the range of 13-24 were classified probable serious mental illness, those in the range 8-12 were classified probable mild-moderate mental illness, and those in the range 0-7 were classified as probable non-cases. A small clinical reappraisal study was carried out with five respondents selected randomly from each of the three categories (serious mental illness, mild-moderate mental illness, non-case). A trained clinical interviewer administered the non-patient version of the Structured Clinical Interview for DSM-IV,27 blinded to the category of each of the 15 respondents. The syndromes assessed were DSM-IV major depressive episode, panic disorder, generalized anxiety disorder, post-traumatic stress disorder, agoraphobia, social phobia and specific phobia. Serious mental illness was defined as a DSM-IV diagnosis with a global assessment of functioning28 score of 0-60 and mild-moderate mental illness as a DSM-IV diagnosis with a global assessment of functioning of > 61. K6 classifications were confirmed for 14 of 15 respondents, the exception being a respondent classified as having severe mental illness by the K6 but mild-moderate mental illness by the structured interview (based on a global assessment of functioning score of 65). Suicidality was assessed by questions about lifetime occurrence of suicidal thoughts, plans and attempts; age at first occurrence of each of these outcomes; and recency of each outcome. Respondents were classified as first-onset cases in respect of each of these outcomes if they reported that the outcome occurred for the first time in their life within the past 12 months (the most recent time frame assessed in the NCS-R).
Sociodemographic correlates assessed included age, sex, race and ethnicity, family income, education, marital status and employment status. Income was coded into a dichotomy of either below the population median for the income-per-family-member ratio versus at or above the median for that ratio.
We also included measures of several dimensions of personal growth occurring after the hurricane (post-traumatic personal growth) that have been found in previous research to occur after exposure to trauma and to facilitate psychological adjustment by making sense of the trauma or finding some positive aspect to the trauma.29,30 We focus on five such dimensions based on their presence in the two most commonly used inventories of post-traumatic personal growth:31,32 post-traumatic increases in emotional closeness to loved ones, faith in the ability to rebuild one's life, spirituality or religiosity, meaning or purpose in life, and recognition of inner strength or competence.
Analysis
Differences in the estimated prevalence of mental illness and suicidality were compared between the NCS-R and the post-Katrina baseline advisory group survey. Sociodemographic variation in between-survey differences was assessed using pooled logistic regression equations predicting outcomes from a 0-1 variable for survey (0 = NCS-R, 1 = post-Katrina survey), the sociodemographic variables, and interactions between the survey and sociodemographic variables. Logistic regression coefficients and their standard errors were exponentiated to create odds ratios (ORs) and their 95% confidence intervals. The role of post-traumatic growth was examined in a subgroup analysis. Because both surveys featured weighting and geographical clustering (NCS-R), analyses used the Taylor series linearization method.33 Multivariate significance was calculated using Wald c² tests based on design-corrected coefficient variance-covariance matrices. Statistical significance was evaluated using two-sided 0.05 level tests.
Findings
Prevalence of mental illness and suicidality
The proportion of respondents estimated to have serious mental illness is significantly higher among those in the post-Katrina sample than the NCS-R (11.3% after Katrina versus 6.1% before; c²1 = 10.9; P = 0.001). The same is true for the proportion estimated to have mild-moderate mental illness (19.9% after Katrina versus 9.7% before; c²1 = 22.5; P < 0.001) and those estimated to have any mental illness (31.2% after Katrina versus 15.7% before; c²1 = 35.9; P <0.001), with ORs in the range 2.0-2.4 (Table 1). The difference between the surveys in suicidality is not significant either for ideation (2.9% after Katrina versus 2.8% before; c²1 = 0.0; P = 0.96), plans (0.7% after Katrina versus 1.1% before; c²1 = 0.4 P = 0.54) or attempts (0.7% after Katrina versus 0.6% before; c²1 = 0.0; P = 0.88).
Suicidal ideation, plans and attempts during the 12 months before the interview were reported in both samples almost entirely by people estimated to have mental illness (results available on request). As a result, the higher estimated prevalence of mental illness but not suicidality in the post-Katrina sample implies that the conditional prevalence of suicidality given probable mental illness is lower among those in the post-Katrina sample than among those sampled before the hurricane. More detailed analysis found that this was especially true for the first onset of suicidality during the past year among respondents with probable mental illness (Table 2). These differences are significant for ideation (0.7% after Katrina versus 8.4% before; c²1 = 13.1; P < 0.001) and plans (0.4% after Katrina versus 3.6% before; c²1 = 6.0; P < 0.014) but not for attempts (0.8% after Katrina versus 2.3% before; c²1 = 1.9; P = 0.17).
Sociodemographic correlates of mental illness and suicidality
Significant sociodemographic correlates of serious mental illness among those in the post-Katrina sample included being non-Hispanic white, not being married before the hurricane, and being classified as having "other" employment status before the hurricane (this mainly included unemployed or disabled people) (Table 3). The only one of these associations that differs significantly when the post-Katrina sample was compared with the NCS-R is a higher prevalence of serious mental illness among people who were not married after Katrina than those who were married before. Suicidal ideation was the focus of a subsequent analysis of suicidality because suicide plans and attempts were too uncommon to be studied with adequate statistical power. The only statistically significant sociodemographic correlates of ideation were being 18-39 years of age and non-Hispanic white (Table 3). The second of these two associations is significantly stronger among those in the post-Katrina sample than those in the NCS-R.
Post-traumatic growth and suicidal ideation
Most respondents to the post-Katrina survey reported the following types of post-traumatic growth: becoming closer to their loved ones (81.6%; 824/1043 in the unweighted data), developing faith in one's own abilities to rebuild one's life (95.6%; 984/1043 in the unweighted data), becoming more spiritual or religious (66.8%; 655/1043 in the unweighted data), finding deeper meaning and purpose in life (75.2%; 752/1043 in the unweighted data) and discovering inner strength (69.5%; 707/1043 in the unweighted data) (Table 4). The probabilities of two of these five vary significantly with mental illness: there is a comparatively low probability of finding deeper meaning and purpose in life among people estimated to have mental illness and there is a comparatively high probability of discovering inner strength among people estimated to have mild-moderate mental illness.
Two of the five dimensions of post-traumatic growth are significantly related to a low prevalence of suicidal ideation among people thought to have mental illness: belief in their own ability to recover and discovery of inner strength (Table 5). The lower prevalence of suicidal ideation in the post-Katrina sample than the NCS-R is limited to those who reported these two aspects of post-traumatic growth, among whom the OR compared with the NCS-R is a statistically significant 0.2. In comparison, the prevalence of suicidal ideation among mentally ill respondents to the post-Katrina survey who had neither of these cognitions does not differ significantly from the prevalence among comparable respondents in the NCS-R, with a stata tistically insignificant OR of 1.1.
Conclusion
The two-survey comparison method is an inexact way to estimate the effects of Hurricane Katrina because the surveys differed in their sampling frames (all households in two Census Divisions in the NCS-R versus households contactable by telephone in areas within these divisions affected by the hurricane in the post-Katrina survey), mode of data collection (face-to-face versus telephone interviews) and response rates. An additional limitation concerns the K6. Although good concordance with clinical interviews has been consistently documented in published reports,23,24 the K6 is merely a screening tool and not a clinical interview.
Notwithstanding these limitations, the fact that the estimated prevalence of serious mental illness and mild-moderate mental illness doubled after Hurricane Katrina is consistent with other evidence of the adverse effects on mental health of major disasters.34,35 The sociodemographic correlates are also largely consistent with previous research.36,37 That the associations among sociodemographic correlates were largely the same across the samples suggests that the adverse mental health effects of Hurricane Katrina were equally distributed across broad segments of the population. Although an analysis of treatment patterns goes well beyond the scope of this report, these results document a high and widely dispersed need for mental health treatment.
Our most striking finding is the lower conditional likelihood of suicidality among people believed to have mental illness after Hurricane Katrina compared with people surveyed before. This finding is not unprecedented. A cross-national epidemiological survey of suicidal ideation found that in Beirut during the first Lebanon-Israel war there was a lower prevalence of suicidal ideation than in any other country studied despite Beirut having a higher prevalence of depression than virtually any other study site.38 While post-hoc methodological interpretations can be constructed (for example, that mental illness associated with exposure to trauma might have a lower intensity that is not detected by standard measures), they seem implausible in light of independent evidence that the severity and impairment of mental illness occurring after disasters are similar when compared with those occurring at other times.39,40
A more plausible explanation is that the effects of increased mental illness after Hurricane Katrina on suicidality were offset by protective factors activated by the hurricane. Although this possibility has not been studied in previous trauma studies, post-traumatic personal growth in areas such as self-efficacy,41 optimism,30 hope42 and perceived social support43 have been documented after disasters, and these changes have been linked to low levels of post-disaster distress.44 Our findings go beyond these earlier results, though, to suggest that some dimensions of post-traumatic personal growth might be protective against suicidality among people with clinically significant mental illness. It is noteworthy that the indicators of post-traumatic growth were not strongly related to our estimates of mental illness, which means that a great many survivors of Katrina are, understandably, depressed by their losses and anxious about their future despite experiencing post-traumatic personal growth. However, the suicidality often associated with these syndromes in the general population is much lower among people in the post-Katrina sample who were able to develop a belief in their ability to rebuild their life and a perception of inner strength in the wake of the hurricane. The causal processes underlying this pattern presumably involve the creation of positive orientations towards the future that provide psychological scaffolding that protects against the suicidality often associated with extreme distress. Although processes of this sort have long been discussed in the psychoanalytic literature,45,46 the current study is, to our knowledge, the first to provide quantitative evidence regarding such a pattern in an epidemiological sample of a population that has survived a disaster.
This finding suggests that further systematic investigation of post-traumatic personal growth might be useful in guiding public health efforts delivered through the mass media in the aftermath of disasters. Research has suggested that public health messages play an important part in affecting psychological reactions to disasters.47-49 The promotion of positive cognitions might be an important pathway for these effects. Systematic research to explore this possibility is needed. In a more immediate way, this finding documents a psychological strength in the population affected by Hurricane Katrina that is, at least temporarily, linked to an unexpectedly low prevalence of suicidality. It is important for public health officials to recognize, though, that this low prevalence of suicidality might be temporary. For example, if the feelings of inner strength reported by so many respondents are linked to an expectation that the practical problems of living created by the hurricane will soon be resolved, and if these expectations are not met as time goes on, one could imagine that the positive cognitions will erode and be replaced with a sense of hopelessness that, in the presence of the high estimated levels of mental illness found here, could lead to a substantial increase in suicidality. The finding of a low prevalence of suicidality, then, should be considered evidence of a short-term postponement rather than of a permanent absence of suicidality in this population. 
Acknowledgements
The writing committee appreciates the helpful comments of the other advisory group scientific collaborators on an earlier version of the manuscript. A complete list of scientific collaborators, publications and respondents' oral histories can be found at http://www.HurricaneKatrina.med.harvard.edu.
Funding: This project was supported by the United States National Institutes of Health research grant number R01MH70884-01A2S1, funded by the National Institute of Mental Health and the Office of the Assistant Secretary for Planning and Evaluation. The funders had no role in the design and conduct of the study; collection, management, analysis and interpretation of the data; and preparation, review or approval of the manuscript.
Competing interests: None declared.
References
1. United States Congress, House of Representatives. A failure of initiative: final report of the Select Bipartisan Committee to Investigate the Preparation for and Response to Hurricane Katrina. Washington, DC: US Government Printing Office; 2006.
2. Louisiana Department of Health and Hospitals. Reports of missing and deceased, 2006. Available from: http://www.dhh.louisiana.gov/offices/page.asp?ID=192&Detail=5248.
3. Claritas. New Hurricane Katrina adjusted population estimates, 2006. Available from: http://www.claritas.com/claritas/Default.jsp?ci=1&pn=Hurricane_katrina_data#updated.
4. Galea S, Ahern J, Resnick H, Kilpatrick D, Bucuvalas M, Gold J, et al. Psychological sequelae of the September 11 terrorist attacks in New York City. N Engl J Med 2002;346:982-7.
5. Smith EM, North CS, McCool RE, Shea JM. Acute postdisaster psychiatric disorders: identification of persons at risk. Am J Psychiatry 1990;147:202-6.
6. Gleser GC, Green BL, Winget C. Prolonged psychosocial effects of disaster: a study of Buffalo Creek. New York, NY: Academic Press; 1981.
7. Goenjian AK, Molina L, Steinberg AM, Fairbanks LA, Alvarez ML, Goenjian HA, et al. Posttraumatic stress and depressive reactions among Nicaraguan adolescents after Hurricane Mitch. Am J Psychiatry 2001;158:788-94.
8. David D, Mellman TA, Mendoza LM, Kulick-Bell R, Ironson G, Schneiderman N. Psychiatric morbidity following Hurricane Andrew. J Trauma ] Stress 1996; 9:607-12.
9. Norris FH, Perilla JL, Riad JK, Kaniasty K, Lavizzo EA. Stability and change in stress, resources, and psychological distress following natural disaster: findings from Hurricane Andrew. Anxiety Stress Coping 1999;12:363-96.
10. Armenian HK, Morikawa M, Melkonian AK, Hovanesian AP, Haroutunian N, Saigh PA, et al. Loss as a determinant of PTSD in a cohort of adult survivors of the 1988 earthquake in Armenia: implications for policy. Acta Psychiatr Scand 2000;102:58-64.
11. Norris FH, Murphy AD, Baker CK, Perilla JL. Postdisaster PTSD over four waves of a panel study of Mexico's 1999 flood. J Trauma Stress 2004;17:283-92.
12. Nandi A, Galea S, Tracy M, Ahern J, Resnick H, Gershon R, et al. Job loss, unemployment, work stress, job satisfaction, and the persistence of posttraumatic stress disorder one year after the September 11 attacks. J Occup Environ Med 2004;46:1057-64.
13. United States Centers for Disease Control and Prevention. Surveillance in Hurricane evacuation centers - Louisiana, September-October 2005. MMWR Morb Mortal Wkly Rep 2006;55:32-5.
14. United States Centers for Disease Control and Prevention. Assessment of health-related needs after Hurricanes Katrina and Rita - Orleans and Jefferson Parishes, New Orleans area, Louisiana, October 17-22, 2005. MMWR Morb Mortal Wkly Rep 2006;55:38-41.
15. Page S. Many evacuees to stay away. USA Today 14 October 2005:1A.
16. Dewan S, Connelly M, Lehren A. 2006 Evacuees' lives still upended seven months after Hurricane. New York Times 22 March 2006:A1.
17. Abramson D, Garfield R. On the edge: children and families displaced by Hurricanes Katrina and Rita face a looming medical and mental health crisis. New York, NY: Columbia University, Mailman School of Public Health; 2006.
18. United States Department of Homeland Security, Federal Emergency Management Agency. Designated counties for Alabama Hurricane Katrina, 2006. Available from:http://www.fema.gov/news/eventcounties.fema?id=4825.
19. United States Department of Homeland Security, Federal Emergency Management Agency. Designated counties for Mississippi Hurricane Katrina, 2006. Available from: http://www.fema.gov/news/eventcounties.fema?id=4807.
20. United States Department of Homeland Security, Federal Emergency Management Agency. Designated counties for Louisiana Hurricane Katrina, 2006. Available from: http://www.fema.gov/news/eventcounties.fema?id=4808.
21. Kessler RC, Merikangas KR. The National Comorbidity Survey Replication (NCS-R): background and aims. Int J Methods Psychiatr Res 2004;13:60-8.
22. Kessler RC, Berglund P, Chiu WT, Demler O, Heeringa S, Hiripi E, et al. The US National Comorbidity Survey Replication (NCS-R): design and field procedures. Int J Methods Psychiatr Res 2004;13:69-92.
23. Kessler RC, Andrews G, Colpe LJ, Hiripi E, Mroczek DK, Normand SL, et al. Short screening scales to monitor population prevalences and trends in non-specific psychological distress. Psychol Med 2002;32:959-76.
24. Kessler RC, Barker PR, Colpe LJ, Epstein JF, Gfroerer JC, Hiripi E, et al. Screening for serious mental illness in the general population. Arch Gen Psychiatry 2003;60:184-9.
25. United States Centers for Disease Control and Prevention. Serious psychological distress: early release of selected estimates based on data from the January - March 2004 National Health Interview Survey, 2004. Available from: http://www.cdc.gov/nchs/data/nhis/earlyrelease/200409_13.pdf.
26. United States Department of Health and Human Services, Substance Abuse and Mental Health Services Administration. 2003 National Survey on Drug Use and Health: results, 2004. Available from: http://www.oas.samhsa.gov/NHSDA/2k3NSDUH/2k3results.htm#ch8.
27. First MB, Spitzer RL, Gibbon M, Williams JBW. Structured clinical interview for DSM-IV axis I disorders: research version. Non-patient edition (SCID-I/NP). New York, NY: New York State Psychiatric Institute, Biometrics Research; 2002.
28. Endicott J, Spitzer RL, Fleiss JL, Cohen J. The Global Assessment Scale: a procedure for measuring overall severity of psychiatric disturbance. Arch Gen Psychiatry 1976;33:766-71.
29. Davis CG, Nolen-Hoeksema S, Larson J. Making sense of loss and benefiting from the experience: two construals of meaning. J Pers Soc Psychol 1998;75:561-74.
30. Dougall A, Hyman K, Hayward M, McFeeley S, Baum A. Optimism and traumatic stress: the importance of social support and coping. J Appl Soc Psychol 2001;31:223-45.
31. Tedeschi RG, Calhoun LG. The Posttraumatic Growth Inventory: measuring the positive legacy of trauma. J Trauma Stress 1996;9:455-71.
32. Park CL, Cohen LH, Murch RL. Assessment and prediction of stress-related growth. J Pers 1996;64:71-105.
33. Wolter K. Introduction to variance estimation. New York, NY: Springer-Verlag; 1985.
34. Galea S, Nandi A, Vlahov D. The epidemiology of post-traumatic stress disorder after disasters. Epidemiol Rev 2005;27:78-91.
35. Norris FH, Friedman MJ, Watson PJ, Byrne CM, Diaz E, Kaniasty K. 60,000 disaster victims speak. Part I: an empirical review of the empirical literature, 1981-2001. Psychiatry 2002;65:207-39.
36. Adams RE, Boscarino JA, Galea S. Social and psychological resources and health outcomes after the World Trade Center disaster. Soc Sci Med 2006;62:176-88.
37. Kessler RC, Berglund P, Borges G, Nock M, Wang PS. Trends in suicide ideation, plans, gestures, and attempts in the United States, 1990-1992 to 2001-2003. JAMA 2005;293:2487-95.
38. Weissman MM, Bland RC, Canino GJ, Greenwald S, Hwu HG, Joyce PR, et al. Prevalence of suicide ideation and suicide attempts in nine countries. Psychol Med 1999;29:9-17.
39. Stuber J, Galea S, Boscarino JA, Schlesinger M. Was there unmet mental health need after the September 11, 2001, terrorist attacks? Soc Psychiatry Psychiatr Epidemiol 2006;41:230-40.
40. Kessler RC, Berglund PA, Bruce ML, Koch JR, Laska EM, Leaf PJ, et al. The prevalence and correlates of untreated serious mental illness. Health Serv Res 2001;36:987-1007.
41. Benight C, Swift E, Sanger J, Smith A, Zeppelin D. Coping self-efficacy as a mediator of distress following a natural disaster. J Appl Soc Psychol 1999;29:2443-64.
42. Cheung YB, Law CK, Chan B, Liu KY, Yip PS. Suicidal ideation and suicidal attempts in a population-based study of Chinese people: risk attributable to hopelessness, depression, and social factors. J Affect Disord 2006;90:193-9.
43. Norris F, Kaniasty K. Received and perceived social support in times of stress: A test of the social support deterioration deterrence model. J Personal Soc Psychol 1996;71:498-511.
44. Johnson Vickberg SM, Duhamel KN, Smith MY, Manne SL, Winkel G, Papadopoulos EB, et al. Global meaning and psychological adjustment among survivors of bone marrow transplant. Psychooncology 2001;10:29-39.
45. Frankl V. Man's search for meaning. London, England: Hodder and Stoughton; 1959.
46. Heisel MJ, Flett GL. Purpose in life, satisfaction with life, and suicide ideation in a clinical sample. J Psychopathol Behav Assess 2004;26:127-35.
47. Vasterman P, Yzermans CJ, Dirkzwager AJ. The role of the media and media hypes in the aftermath of disasters. Epidemiol Rev 2005;27:107-14.
48. Ahern J, Galea S, Resnick H, Kilpatrick D, Bucuvalas M, Gold J, et al. Television images and psychological symptoms after the September 11 terrorist attacks.Psychiatry 2002;65:289-300.
49. Ahern J, Galea S, Resnick H, Vlahov D. Television images and probable posttraumatic stress disorder after September 11: the role of background characteristics, event exposures, and perievent panic. J Nerv Ment Dis 2004;192:217-26.
(Submitted: 5 May 2006 - Final revised version received: 2 August 2006 - Accepted: 11 August 2006)
1 Correspondence should be sent to Dr Kessler (email: kessler@hcp.med.harvard.edu).