Institute of Public Health, College of Medicine, National Cheng Kung University, Tainan, Taiwan, Address: No. 1, Da Hsueh Road, Tainan 701, Taiwan. E-mail: robertlu{at}mail.ncku.edu.tw
SirsDurkheim concluded that the suicide rate can only be explained sociologically, because:
The suicide victim's acts, which at first seem to express only his personal temperament are really the supplement and prolongation of a social condition, which they express externally.1
Though it is the individual who commits suicide, many of the traits and states of the individual are shaped by a broader socioeconomic context.2 It was not the shock of the earthquake that made people commit suicide; it was the quarrels among families regarding sharing the financial burden of rebuilding the house, the poor control of mental disease owing to the disorganized healthcare systems, the lack of social and financial support during the harsh rebuilding process, the powerlessness, and the frustrations caused by a corrupt bureaucracy that made people commit suicide. All these immediate causes of suicide were institutionalized in the organizations, cultural norms, social networks, economic opportunities, power structures, globalization etcthe context.
Why was the impact of an earthquake on suicides so small?
Chou et al. were puzzled about the small impact of an earthquake on suicides compared with other life stresses, like the death of a spouse.3 For a large study population (n = 3 432 705), the odds ratio (OR) of victims committing suicide was only 1.46 (95% CI: 1.11, 1.92) in their study, as against the OR for loss of a spouse ranging from 3.91 for women to 4.09 for men in a Finnish study cited by the authors.3 I think the main reason for the observed small impact of an earthquake on suicide was that the authors did not bring the contextual effects into the analysis, i.e. the effects of group-level properties on individual-level outcomes.4
In their study, the victims were those who received quake cards exempting them from cost-sharing under the National Health Insurance (NHI) programme after the 1999 earthquake. Quake cards were issued to survivors whose houses had been destroyed or whose families had been injured or killed. Many of the victims belonged to the same family, the same building, the same block and the same community, because the earthquake struck along the line of geological fault. There were great socioeconomic variations among different families, buildings, blocks and communities in different lines of the geological fault. The category of victims was actually composed of a heterogeneous mix with different contextual characteristics. Given the same stressful earthquake event, victims in different contexts have different adaptation abilities.
Nantou County was the most seriously damaged county during the 1999 Taiwan earthquake. Table 1 shows 13 areas in Nantou County that suffered different degrees of damage, i.e. the direct earthquake-related death rate and the percentage of households destroyed. No association, however, was found between the degree of damage and the increase in suicide rate, no matter which statistical tests were used. For example, Chungliao, the area that suffered most during the earthquake, showed no increase in suicide rate. On the other hand, Mingchien, an area with a low degree of damage, nonetheless experienced the highest increase in suicide rate after the earthquake. Why was there no association between the degree of damage and the increase in suicide rate?
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Another reason for the observed small impact of earthquake on suicide was that the earthquake would affect everyone in the affected area regardless of whether their houses had been destroyed or their families injured or killed. Non-victims also suffered from the inconveniences resulting from the destruction of public goods, such as public traffic roads, hospitals, banks, post offices, schools, water resources and electric equipment, by the earthquake. Though the earthquake did not injure or kill non-victims' co-resident families, it injured and killed their close neighbours, friends and relatives. Both victims and non-victims suffered from diffuse distressing effects of the earthquake. It is not surprising that the difference between victims and non-victims in the chance of committing suicide was small. Accordingly, I do not agree with the authors' suggestion that mental health programmes or other preventive strategies might be more effective if specifically targeting victims. As Macintyre cautioned, this kind of study treats individual characteristics as being independent of the larger social and physical environment.7
The right answer for the wrong question?
The authors concluded that individual victim status is an important explanatory factor in understanding the effect of earthquakes on suicide. They also explicitly stated that their individual-level study was better than previous ecological disaster studies.3 Ross reminded us that we must distinguish immediate or proximal causes of disease and the causes of causes, i.e. the determinants of unequal distribution of exposure to the risks.8 According to his argument, the answer to why did some people commit suicide and not others?' would be in a different form to the answer to why is the suicide rate higher in group A than in group B? or why is the suicide rate increasing in country A?.
Individual-level epidemiological studies can answer only the first question, i.e. the causes that distinguish individuals within a population. If the question is the cause of an increase in suicide rate or differences in the suicide rates between populations, however, and researchers use methods addressing inter-individual differences to answer the question, they are committing a type III error, i.e. providing a right answer for the wrong question.9 Lu argued that injury epidemiologists were more likely to run the risk of type III error because many of the factors related to the incidence of injury are contextual characteristics, e.g. road construction, legislation and enforcement of safety measures, drinking culture, etc.10
Traditional individual-level epidemiological studies cannot detect causes that are either widespread or relatively invariant within the population under study. Only through the study of the different levels of contextual characteristics can we find the variances. According to Table 1, we found a huge variance in standardized mortality ratio (SMR) of suicide rates before the earthquake at the area level, ranging from 64 in Mingchien to 371 in Hsienyi, which was greater than that found at the individual level. This means that factors other than the earthquake resulted in the differences in suicide rates between areas.
Figure 1 shows the suicide rate changes from 1981 through 2002. Both Nantou and Taiwan showed an increase in suicide rates starting from 1993, 6 years before the earthquake struck. Before the 1999 earthquake, Nantou County already showed a faster increase in suicide rate than did Taiwan as a whole. After the 1999 earthquake, the rate of increase in suicide rate in Nantou was slightly greater than the rate of increase in Taiwan. The pattern of suicide changes corresponded well with changes in unemployment rates. A previous study indicated that, as Taiwan became more industrialized, people were more susceptible to short-term cyclical fluctuation in economic performance as revealed by the unemployment rate.11 Taiwan also was not immune to the economic crisis that struck all Asian countries in the late 1990s.
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References |
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2 Makinen IH, Wasserman D. Some social dimensions of suicide. In: Wasserman E (ed.). Suicide: An Unnecessary Death. London: Marin Dunitz, 2001, pp. 99108.
3 Chou YJ, Huang N, Lee CH et al. Suicides after the 1999 Taiwan earthquake. Int J Epidemiol 2003;32:100714.
4 Diez-Roux AV. Bringing context back into epidemiology: variables and fallacies in multilevel analysis. Am J Public Health 1998;88:21622.[Abstract]
5 921 Earthquake Relief Foundation. At: http://www.921fund.org.tw (accessed 20 January 2004).
6 Yang ML. Rebuild a hometown with ecology and memory. Common Wealth 1999;223:5666. (In Chinese).
7 Macintyre S, Ellaway A. Ecological approaches: rediscovering the role of the physical and social environment. In: Berkman LF, Kawachi I (eds). Social Epidemiology. New York: Oxford University Press, 2000.
8 Rose G. The Strategy of Preventive Medicine. Oxford: Oxford University Press, 1992.
9 Schwartz S, Carpenter KM. The right answer for the wrong question: consequences of type III error for public health research. Am J Public Health 1999;89:117580.[Abstract]
10 Lu TH. International comparisons do help and are essential for avoiding type III error in injury prevention research. Inj Prev 2001;7:27071.
11 Chuan HL, Huang WC. A reexamination of sociological and economic theories of suicide: a comparison of the U.S.A. and Taiwan. Soc Sci Med 1996;43:42123.[CrossRef][ISI][Medline]