Liverpool University, Liverpool, and Hollins Park Hospital, Warrington WA2 8WA, UK. Tel: 01925 664123; fax: 01925 664145
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ABSTRACT |
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Aims To assess the effect of 11 September 2001 on the rate of suicide and homicide in England and Wales.
Method Analysis of the number of suicides (ICD9 codes: E950E959), undetermined injury deaths (E980E989) and homicides (E960E969) in England and Wales in the 12 weeks before and after 11 September 2001 and during a similar period in the previous two years.
Results The number of suicides reported in the month of September 2001 was significantly lower than other months in the same year and any September of the previous 22 years in England and Wales. A suicide reduction in men, regardless of age, occurred in the week starting Tuesday 11 September 2001. A reduction in female suicide occurred during the four weeks following the attack.There was no evidence of a similar effect on homicide.
Conclusions The tragic events of 11 September 2001 appear to have had a brief but significant inverse effect on suicide.The finding of this study supports Durkheims theory that periods of external threat create group integration within society and lower the suicide rate through the impact on social cohesion.
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INTRODUCTION |
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METHOD |
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Daily counts of suicide and homicide were aggregated into weekly counts from Tuesday to Monday, so that they would contain the week starting with Tuesday 11 September 2001. Aggregation of data was carried out for the three years 1999, 2000 and 2001.
Statistical analysis
Weekly means of suicide and homicide before and after the week of 11
September 2001 were compared. Any differences were compared with figures
observed during the same periods in 1999 and 2000 as a means of adjusting for
seasonal variations and the recent decline in suicide
(Kelly & Bunting,
1998).
The goodness-of-fit 2-test was used to compare observed and
expected counts of monthly and annual suicides and homicides. The
KruskalWallis test was used to compare counted weekly data during the 3
months before and after 11 September and to compare daily, weekly and monthly
means when applicable (e.g. means of suicide and homicide computed for
previous years).
Daily variations in suicides occurring in September for 2001 and previous
years and variations in observed weekly counted mortality data for 2001
compared with expected data based on figures from previous years were assessed
by applying control chart statistics: application of time-series methods to
assess the occurrence of events such as suicide and homicide over a period of
time based on the Poisson mean. If the data follow a distribution that
indicates a regular occurrence of events (such as suicide) over a period of
time then the variance is equal to the mean (C) and the standard
deviation is equal to the square root of the average C, that is:
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RESULTS |
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Figures 4, 5, 6 show the reported mean number of weekly suicides for men and women 12 weeks before and after the week of 11 September 2001. The average total number of suicides in the week starting 11 September 2001 was 100, which is not significantly different from the overall mean in the 12 weeks before and after the event: 109 and 102, respectively (P > 0.05). However, this was significantly lower than the observed value of 120 during the same September week in the previous years (P < 0.05).
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The number of male suicides in the week of 11 September 2001 was 68, which is significantly lower than the overall mean in the 12 weeks before and after the event: 82 and 84, respectively (P < 0.05). The number of reported suicides in the week of 11 September 2001 also was significantly lower than the 99 observed during the same week in previous years (P < 0.05) (Fig. 5).
The reduction in male suicides was more evident in men aged less than 50 years but the difference did not reach statistical significance. Over the four weeks after 11 September 2001 the reduced suicide counts appear to have reverted back to the expected level for 2001 before the event. The reduction in male suicides during the week of 11 September did exceed the control chart lower control limit at P < 0.05 (i.e. expected mean two standard deviations) but was not significant at P < 0.01 (i.e. expected mean three standard deviations).
The reduction in female suicides did not reach statistical significance and occurred during the four weeks following the attack and not during the same week as in men (Fig. 6).
Homicide
September-reported homicides and total annual homicides in England and
Wales between 1979 and 2001 are shown in
Table 1.
Figure 7 shows the number of
homicides in 2001 compared with the monthly means computed for ten years in
the 1980s and 1990s, respectively. No significant difference was found
regarding the homicides that occurred in September 2001. However, the graph
shows a significant trend in the lower rate of homicide after August to
December (2=32, d.f.=11; P < 0.01), which is
evident in 2001, the 1980s and the 1990s.
Figure 8 illustrates the same
trend for homicide. No significant difference in homicide weekly means was
found before or after 11 September 2001. The mean number of weekly homicides
was higher in 2001 compared with previous years except for the week of 11
September (Fig. 8). The mean
difference, however, did not reach statistical significance.
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DISCUSSION |
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There was no evidence of a similar reduction in reported homicides. Homicide was observed to have a consistent seasonal increase in May and a decline after August but this was unrelated to the events of 11 September.
Although there is an association between suicide and suicidal behaviour and homicide and violence to others (Van Praag, 2000), there is no literature currently available detailing the effect of suicide terrorism, particularly the attacks of 11 September, on the rate of suicide and homicide.
Murder and suicide may be inseparable as both assert power over death (Dein & Littlewood, 2000). Individual murderers may seek the death penalty for themselves through suicide. Simultaneous suicide and homicide has become a hallmark of suicide terrorism (Salib, 2003). Suicide terrorism, which is seen by the perpetrators as a mode of warfare, is aimed at causing devastating physical damage and inflicting profound fear on an entire population rather than just the victims of the actual attack, aided by extensive, dramatic and spectacular media coverage (Salib, 2003). There is a need for responsible media reporting of terrorist acts, given the potential mental health impact. Media reporting of deaths and disaster-related television viewing can cause severe distress and also influence the suicide rate (Bollen & Phillips, 1982).
The televised national shock and public display of grief over the death of Diana, Princess of Wales and after her funeral in 1997 was shown to have influenced the rate of suicidal behaviour and deliberate self-harm (Hawton et al, 2000). The repeated viewing of the tragic scenes of 11 September live acts of simultaneous mass homicide and suicide appears to have had a brief but significant inverse effect on suicide in England and Wales. Imitative suicide (Bollen & Phillips, 1982) was reported in one incident shortly after 11 September (the shoe bomber). It is not clear why the reduction in suicide was only evident in men but this may be related partly to the fact that all the terrorists were men and the visibly distressed fire-fighters and other rescue workers were men. The temporary reduction in suicide associated with 11 September is probably not dissimilar to what has been reported during major wars. Suicide rates declined during the world wars of the 20th century, both in men and women and in participating and non-participating nations (Lester, 1995). Also, following the assassination of President John F. Kennedy in 1963 there was a reported reduction in suicide rate in the USA (Biller, 1977).
The finding of this study supports Durkheims theory that periods of external threat and major events create group integration within society and lower the suicide rate through the impact on social cohesion (Durkheim, 1897). It also supports Durkheims views that imitation does not significantly affect suicide rates, a view that is not shared explicitly by modern sociologists (Bollen & Phillips, 1982). Suicide and homicide data for 2002 were not available at the time of writing this paper to assess the effect of the first anniversary of 11 September 2001.
Limitations of the study
One of the main problems associated with using routinely collected data, no
matter how reliable and complete, is that of misclassification of data. It
must be emphasised that it is impossible to rule out entirely the effect of
chance fluctuations in suicide rate or other influences that might explain the
findings. The study did not examine whether the observed reduction in male
suicides was attributable to a drop in the use of violent methods
(particularly explosives, self-immolation and falling from heights) or to a
reduction in non-violent deaths. The study did not examine the effect of 11
September on deliberate self-harm behaviour.
Future research
The study findings could be tested by future similar studies from the USA
and other countries that may assess the effect of 11 September on suicide and
homicide in persons with mental illnesses and also on deliberate self-harm
behaviour, areas that the present study did not cover. The effect of ethnic,
religious and cultural difference on the rate of suicide after 11 September
2001 within the USA itself and elsewhere also should be explored.
The effect of 11 September anniversaries on suicide and homicide rates, especially with further detailed and dramatic media coverage, may be of interest to future researchers.
Another area for future research is to assess the frequency, targets, locations, groups and outcome of suicide bombing and other forms of suicidehomicide acts after 11 September 2001.
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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REFERENCES |
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Biller, O. A. (1977) Suicide related to the assassination of President John F. Kennedy. Suicide and Life Threatening Behaviour, 7, 4044.
Bollen, K. A. & Phillips, D. P. (1982) Imitative suicides: a national study of the effect of television news stories. American Sociological Review, 47, 802809.
Dein, S. & Littlewood, R. (2000) Apocalyptic suicide. Mental Health, Religion & Culture, 3, 109114.
Durkheim, E. (1897) Le Suicide (English translation, 1951). Glencoe, Il: Free Press.
Galea, S., Vlahov, D., Resnick, H., et al (2002) An investigation of psychological effects of September 11, 2001, attacks on New York City: developing and implementing research in acute post disaster period. CNS Spectrums, 7, 585587, 589596.
Hawton, K., Harriss, L., Appleby, L., et al
(2000) Effect of death of Diana, Princess of Wales on suicide
and deliberate self-harm. British Journal of
Psychiatry, 177,
463466.
Kelly, S. & Bunting, J. (1998) Trends in suicide in England and Wales 198296. Population Trends, 92, 2941.[Medline]
Lee, A., Isaac, M. & Janca, A. (2002) Post-traumatic stress disorder and terrorism. Current Opinion in Psychiatry, 15, 633637.[CrossRef]
Lester, D. (1995) Suicide rates before and after the world wars. European Psychiatry, 9, 262264.
Salib, E. (2003) Suicide terrorism: a case of
folie à plusieurs? (editorial). British Journal of
Psychiatry, 182,
475476.
World Health Organization (1977) Manual of the International Statistical Classification of Diseases, Injuries and Causes of Death (9th revision) (ICD9). Geneva: WHO.
Van Praag, H. (2000) Suicide and aggression: are they biologically two sides of the same coin? In Suicide and Prevention: Resources for the Millennium (ed. D. Lester), pp. 4564. Hove: Taylor and Francis.
Wetherill, G. B. & Brown, D.W. (1994) Statistical Process Control, Theory and Practice. London: Chapman & Hall.
Received for publication February 12, 2003. Revision received May 28, 2003. Accepted for publication June 3, 2003.
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