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 The world suffers from many natural disasters, which affect about 200 million people and kill several thousand each year (1). A recent example is the tsunami and tremors that struck Indonesia, southern Thailand, and Sri Lanka on 26 December 2004, killing over 104 000 people in Indonesia and over 5000 in Thailand (2). Similarly, Hurricane Mitch (which struck Nicaragua in 1998) directly affected 2 million people. Some 4000 died, and 500 000 were left homeless (3). Flood is one of the most common and most severe forms of natural disasters, accounting for up to one-half of all natural disasters (1). In China, natural disasters are frequent. A severe flood that struck China’s Hunan province in 1998 and 1999 left hundreds of thousands of residents homeless. Much of the infrastructure and many agricultural projects were damaged as well. Floods can lead to direct economic and property losses and result not only in physical injuries and deaths but also in psychological injuries. PTSD is a commonly used indicator to evaluate psychological injuries after disaster. Previous studies have assessed the impact of floods in terms of property loss, mortality, and morbidity (4). However, only a few such studies have reported PTSD in flood victims (5–7), and none are from China. PTSD is a severe and complex disorder precipitated by exposure to a psychologically distressing event (8). In the past decade, the study of PTSD has focused on traffic accidents (9,10), violent crimes (11), terrorist attacks (12–14), hurricanes (3), earthquakes (15), hijackings (16), rapes (17), and warfare (18), with little attention being paid to flood. Our study aims to estimate the incidence of PTSD in flood victims and to assess risk factors for PTSD after a flood. MethodsStudy Area and Study Population Victims who had been directly exposed to the 1998–1999 floods in Hunan, China, formed the target population. We used a multistage sampling method to select study subjects. In the first stage of sampling, we randomly selected 8 counties (7 with damage from soaking and collapsed embankments and 1 that experienced flash flooding) from 38 affected counties (of which 33 experienced damage from soaking and collapsed embankments and 5 experienced flash flooding). In the second stage of sampling, we randomly selected 40 townships (50%) from the 8 study counties. In the third stage of sampling, we randomly selected 310 villages (50%) from the study townships. Finally, we randomly selected 13 450 households (50%) from the study villages. All family members of the study villages who were aged 7 years or over were asked to participate. Flooding was classified into 3 types: soaked flood, collapsed embankment, and flash flood. Flooding was also divided into 3 groups by severity: mild (affected area < 50%), intermediate (affected area 50% to 75%), and severe (affected area ≥ 75%). Ascertainment of PTSD and Collection of Demographic Data Between January and May 2000, trained research assistants carried out face-to-face interviews (with on-site supervision by psychologists), using a preconstructed questionnaire. The sampled study subjects were interviewed to ascertain PTSD and to collect demographic data. The diagnosis of PTSD was made according to the DSM-IV (19) criteria, which include 17 symptoms scored as 0 = none, 1 = slight, 2 = moderate, 3 = severe, and 4 = extreme. Subjects whose score was equal to or greater than 2 were defined as positive. The 17 symptoms of PTSD were further divided into 3 groups, representing 3 diagnostic criteria: B, C, and D. Criterion B symptoms represent the reexperiencing cluster: B1, intrusive recollections; B2, repeated nightmares about floods; B3, acting as if the flood is occurring; B4, feeling worse when reminded of the flood; and B5, reactivity to flood reminders. Subjects were defined as positive if they showed one or more positive items in the B group. Crtierion C symptoms make up the avoidance cluster and include the following: C1, efforts to avoid thoughts or feelings associated with the flood; C2, efforts to avoid activities that arouse recollections of the flood; C3, amnesia in regard to the flood; C4, diminished interest; C5, detachment or estrangement; C6, restricted range of affect; and C7, sense of foreshortened future. Subjects were defined as positive if they showed 3 or more positive items in the C group. Criterion D symptoms make up the hyperarousal cluster: D1, difficulty falling or staying asleep; D2, irritability or anger; D3, difficulty concentrating; D4, hypervigilance; and D5, exaggerated startle response. Subjects were defined as positive if they showed 2 or more positive items in the D group. Subjects were given a diagnosis of PTSD if Criterion B, C, and D symptoms were all positive. We assessed all symptoms, including the time of the symptom occurrence and the duration of the symptom. Data Analysis We first described the characteristics of the study areas and study populations. We then compared the rates of PTSD among groups experiencing different flood types and severity levels, as well as among different sex and age groups. Adjusted ORs (95%CIs) for PTSD were estimated with multiple logistic regression models. PTSD was the dependent variable. Independent variables included in the initial regression model were sex and age of the study subjects and flood type and flood severity experienced. A stepwise procedure was used in the regression modelling process, with the entry threshold set at P = 0.05 and the exit threshold set at P = 0.10 for all variables. All analyses were performed with SPSS Version 11.0 (SPSS, Chicago, IL). ResultsA total of 8 counties, 40 towns, 310 villages, 13 450 households, and 38 760 individuals aged 7 years or older were selected for study. Of the 38 760 selected study subjects, 33 340 (86.0%) were interviewed: 14 349 (43.1%) from the flood-soaked group, 13 893 (41.7%) from the collapsed embankment group, and 5053 (15.2%) from the flash flood group. Table 1 displays details of the study areas and study populations.
A total of 2875 study subjects were diagnosed with PTSD, yielding an incidence of 8.6%. The flash-flooding areas had the highest rate of PTSD (16.8%), followed by areas of collapsed embankment (10.4%). The rates of Criterion B, C, and D syndromes were 22.4%, 13.3%, and 26.5%, respectively. The risk of PTSD increased in female and older victims and in victims from collapsed embankment and flash-flood areas or from intermediately or severely affected areas (Table 2).
DiscussionOur study ascertained PTSD from a sample of 33 340 flood victims (86.0% of the selected study subjects). The overall incidence of PTSD was 8.6%, and the occurrences for the 3 groups of symptoms (B, C, and D) were 22.4%, 13.3%, and 26.5%, respectively. To our knowledge, this is the largest study using a diagnosis of PTSD to assess the impact of floods on victims’ psychological health. PTSD is a common psychological disorder in disaster-affected populations. It has been widely used to evaluate the psychological impact of natural disasters, accidents, and war (9–18). The 8.6% PTSD rate found in the flood-affected victims observed our study was lower than that found by Wang and others among earthquake victims (24.2%) (15) or than that observed by Zhou and others among rock-fall victims (43%) (20). Similarly, it was lower than that estimated by Liu and others for victims of traffic accident (38.27%) (9). Differences in the nature and severity of different types of disasters, in populations studied, and in study methodology make it difficult to reconcile the results from different studies. Our study found that the risk of PTSD was higher in female victims than in male victims. This finding is consistent with previous studies (21–25) and suggests that women may be more sensitive to the impact of flood than men. Our study also found that victims aged 18 years or over had higher PTSD rates than did victims under age 18 years. Several studies have also observed an increased risk of PTSD after natural catastrophes in victims aged 35 to 54 years (26– 29). Possibly, the explanation for the observed association between age and PTSD is, again, that older victims are more sensitive than younger victims to floods or other natural disasters. The associations between flood type and PTSD and flood severity and PTSD are expected and lend validity to our study findings. If floods cause PTSD, there should be a gradient of the relation from bad (soaked) to worse (collapsed embankment) to the worst (flash) type of flood and from floods that are mild to intermediate to severe. ConclusionOur large, population-based study suggests that PTSD occurs in about 8% to 9% of flood victims and that the risk of PTSD increases in female and older victims and varies by type and severity of flood. Funding and SupportThis project was supported by grant CMB 98-689 from the Chinese Medicine Board (New York). AcknowledgementsThe authors thank Linbao Xiang, director of the Center of Disease Prevention and Control (CDC) of Yiyang city; Xiumin Zhang, director of the CDC of Anxiang county; Huaxian He, director of the CDC of Yueyang city; Linlin Li, director of the CDC of Xiangxi autonomy; and Senlin Tang, director of the CDC of Datong Lake District, all located in Hunan, China, for their cooperation in this study. References1. International Federation of Red Cross and Red Crescent Societies. World disasters report 2002. Available: www.ifrc.org/publicat/wdr2002/chapter8.asp. Accessed 2006 Mar 13. 2. International Charter: Space and Major Disasters. Tsunami, Indonesia and Thailand. Available: www.disasterscharter.org/disasters/CALLID_079_e.html. Accessed 2006 Mar 13. 3. Goenjian AK, Molina L, Steinberg AM, Fairbanks LF, Alvarez ML, Goenjian H, and others. Posttraumatic stress and depressive reactions among Nicaraguan adolescents after Hurricane Mitch. Am J Psychiatry 2001;158:788–94. 4. Wang M. Distribution and main character of related diseases after flood. Disaster Reduction 2000;3:156–9. 5. North CS, Kawasaki A, Spitznagel EL, Hong BA. The course of PTSD, major depression, substance abuse, and somatization after a natural disaster. J Nerv Ment Dis 2004;12:823–9. 6. Norris FH, Murphy AD, Baker CK, Perilla JL. Postdisaster PTSD over four waves of a panel study of Mexico’s 1999 flood. 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In: Coates SW, Rosenthal JL, Schechter DS, editors. September 11. Trauma and human bonds. Hillsdale (NJ): The Analytic Press; 2003. p 75–9. 13. Delisi LE, Maurizio A, Yost M, Papparozzi CF, Fulchino C, Katz CL, and others. A survey of New Yorkers after the Sept. 11, 2001, terrorist attacks. Am J Psychiatry 2003;160:780–3. 14. Jehel L, Paterniti S, Brunet A, Duchet C, Guelfi JD. Prediction of the occurrence and intensity of post-traumatic stress disorder in victims 32 months after bomb attack. Eur Psychiatry 2003;18:172–6. 15. Wang XD Gao L, Shinfuku N Zhang HB, Zhao CZ, Shen YC, and others. Longitudinal study of earthquake-related PTSD in a randomly selected community sample in North China. Am J Psychiatry 2000;157:1260–6. 16. Vila G, Porche LM, Mouren-Simeoni MC. An 18-month longitudinal study of posttraumatic stress disorders in children who were taken hostage in their school. Psychol Med 1999;61:746–54. 17. Acierno R, Resnick H, Kilpatrick DG, Saunders B, Best CL. Risk factors for rape, physical assault, and posttraumatic stress disorder in woman: examination of differential multivariate relationships. J Anxiety Disord 1999;13:541–63. 18. Marmar CR, Weiss DS, Schlenger WE. Peritraumatic dissociation and posttraumatic stress in male Vietnam theater veterans. Am J Psychiatry 1994;151:902–7. 19 American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 4th ed. Washington (DC): APA; 1994. 20. Zhou JC, Zhou CL, Zhang SG. Investigation of spirit reaction to rock fall and hanging bridge in Wuxi County. Chinese Journal of Psychiatry 1998;2:72–5. 21. Kessler RC, Sonnega A, Bromet E, Hughes M, Nelson CB. Posttraumatic stress disorder in the National Comorbidity Survey. Arch Gen Psychiatry 1995;52:1048–60. 22. Breslow N, Davis GC, Andreski P, Peterson EL, Schultz LR: Sex differences in posttraumatic stress disorder. Arch Gen Psychiatry 1997;54:1044–8. 23. Carr VJ, Webster RA, Hazell PL, Kenardy JA, Carter GL. Psychosocial sequelae of the 1989 Newcastle earthquake, community disaster experiences and psychological morbidity 6 months post-disaster. Psychol Med 1995;25:539–55. 24. Gibbs MS: Factors in the victim that mediate between disaster and psychopathology: a review. J Trauma Stress 1989;2:489–514. 25. Smith EM, North CS: Post-traumatic stress disorder in natural disasters and technological accidents. In: International handbook of traumatic stress syndrome. Wison JP, Raphael B, editors. New York (NY): Plenum; 1993. p 405–19. 26. Goenjian AK, Najarian LM, Pynoos RS, Steinberg AM, Manoukian G, Tavosian A, and others. Posttraumatic stress disorder in elderly and younger adults after the 1988 earthquake in Armenia. Am J Psychiatry 1994;151:895–901. 27. Thompson MP, Norris FH, Hanacek B. Age differences in the psychological consequences of Hurricane Hugo. Psychol Aging 1993;8:606–16. 28. Gleser GC, Green BL, Winget CN. Prolonged psychosocial effects of disaster: a study of Buffalo Creek. New York (NY): Academic Press; 1981. 29. Price J. Some age-related effects of the Brisbane floods. Aust N Z J Psychiatry 1978;12:55–8. Author(s)Manuscript received May 2005, revised, and accepted January 2006. 1. Associate Professor, School of Public Health, Central South University, Changsha, Hunan, PR China; International Fellow, OMNI Research Group, Department of Obstetrics and Gynecology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario. 2. Professor, School of Public Health, Central South University, Changsha, Hunan, PR China. 3. Lecturer, School of Public Health, Central South University, Changsha, Hunan, PR China. 4. Associate Professor, School of Public Health, Central South University, Changsha, Hunan, PR China. 5. Assistant Professor, Brock University, St Catharines, Ontario. 6. Instructor, School of Public Health, Central South University, Changsha, Hunan, PR China. 7. Visiting Professor, School of Public Health, Central South University, Changsha, Hunan, PR China; Associate Professor, OMNI Research Group, Department of Obstetrics and Gynecology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario. Address for correspondence: Dr A Liu, School of Public Health, Central South University, Xiangya Road 110, Changsha, Hunan 410008, PR China e-mail: laz@xysm.net or liu_aizhong@hotmail.com
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