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Deliberate Self-Poisoning in Ontario Following the Terrorist Attacks of September 11, 2001
To the Editor: The terrorist attacks in the United States on September 11, 2001, caused significant medical and psychiatric morbidity, particularly in Manhattan, and acutely disrupted the lives of people around the world.1 However, little research has examined the effects of September 11 outside the United States. We hypothesized that the attacks influenced rates of deliberate self-harm, a complex behavioral phenomenon that includes deliberate self-poisoning. We conducted an ecological analysis of poisonings in the days immediately following September 11 in a population geographically removed from the events.
Methods
We identified all hospitalizations for self-poisoning in Ontario during the month of September from 1988 to 2003 using the population-based records of the Canadian Institutes of Health Information (International Classification of Diseases, Ninth Revision codes 960.0-990.0 and International Statistical Classification of Diseases, 10th Revision codes T36-T50.) To exclude instances of accidental toxicity, we restricted the analysis to poisonings in which the external cause of injury code indicated deliberate self-harm.2 We excluded more violent means of suicide (such as gunshot and hanging) because these are frequently fatal and may not lead to hospital admission. To examine the possibility that the results could reflect a generalized change in hospitalization or coding practices, we repeated the analyses using admissions for pneumonia, unstable angina, asthma, and congestive heart failure, diseases not governed by impulse.
The primary analysis examined admissions during the 3-day period beginning on the second Tuesday in September of each year, corresponding to September 11-13, 2001. We studied a 3-day interval because we anticipated an immediate but transient effect of the terrorist attacks and because research from Israel suggests that terrorist attacks reduce motor vehicle accidents for a similar period.3 In sensitivity analyses, we changed the observation period following September 11 from 3 days to 2 days and then to 4 days.
Time-series analysis with autoregressive integrated moving average modeling was used to forecast the expected number of poisoning admissions during the corresponding 3-day periods in 2001, 2002, and 2003.4 All P values were 2-sided and used a significance threshold of .05. Analyses were conducted using SAS, version 8.2 (SAS Institute Inc, Cary, NC).
Results
From 1988 to 2003, we identified 6077 hospital admissions for deliberate self-poisoning in Ontario during September. Of these, 614 occurred during the 3-day period beginning on the second Tuesday of the month. In 2001, there were 13 admissions during this period, about 64% fewer than the predicted number of 36 (95% confidence interval, 25-46; P<.001) (Figure). No similar phenomenon was seen when the analysis was repeated using the 3-day period before (Saturday, Sunday, and Monday) or after (Friday, Saturday, and Sunday) the same 3 days in September. The findings persisted when we changed the observation period to 2 days or 4 days following September 11 (63% and 53% fewer than predicted, respectively; P = .002 for both comparisons). In contrast, the number of poisoning admissions in 2002 and 2003 did not differ significantly from predicted estimates. Men constituted a lower proportion of poisonings from September 11 to 13, 2001, compared with the same period in all other years (8% vs 46%; P = .03).
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Figure. Number of Hospital Admissions for Deliberate Self-Poisoning in Ontario During the 3-Day Period Beginning on the Second Tuesday in September, 1988-2003
The blue data plot beginning in 2001 indicates the projected number of poisoning admissions (and 95% confidence intervals) derived from time series analysis.
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Repeating the analyses using admissions for pneumonia, unstable angina, asthma, and congestive heart failure showed no significant change in admissions for these conditions in the 3 days following September 11, 2001.
Comment
Most studies of the consequences of the September 11 terrorist attacks in patients living outside New York and Washington, DC, have examined trends in anxiety-related diagnoses over extended periods.5-6 Two European studies suggest slight changes in suicide rates in the months after September 11, but with inconsistent findings.7-8 In contrast, we found that the terrorist attacks were associated with a transient but dramatic reduction in deliberate self-poisoning in Ontario, suggesting that some determinants of self-harm behavior can be temporarily suppressed by major world events.
The decline in self-poisoning may have occurred because the enormity and unexpectedness of the terrorist attacks produced profound but transient mass distraction at the population level, causing people to temporarily set aside their own personal difficulties. Suicide attempts are often triggered by acute personal crises.9 Some stressors may not have occurred or may have assumed lesser significance given the scale of the terrorist attacks.
These results are unlikely to be spurious given the statistical significance and the absence of similar effects with other medical conditions. However, these findings need to be replicated in other locales and by studying other forms of deliberate self-harm before the effect can be generalized.
Access to Data: Dr Juurlink had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Financial Disclosures: None reported.
Funding/Support: Drs Austin and Juurlink are supported by New Investigator Awards from the Canadian Institutes for Health Research. Dr Juurlink is also supported by the University of Toronto Drug Safety Research Group.
Role of the Sponsor: The funding sources had no role in the design and conduct of the study, in the collection, management, analysis, and interpretation of the data, or in the preparation, review, and approval of the manuscript.
Previous Presentation: Presented at the North American Congress of Clinical Toxicology, September 13, 2005, Orlando, Fla.
Acknowledgment: We are grateful to Allan Detsky, MD, PhD, and Donald Redelmeier, MD, MSc, Department of Medicine, University of Toronto, and Muhammad Mamdani, PharmD, Institute for Clinical Evaluative Sciences, for their helpful comments.
Michael E. Detsky, BSc
Department of Medicine
University of Toronto
Toronto, Ontario
Marco L. A. Sivilotti, MD, MSc
Department of Pharmacology and Toxicology
Queen’s University
Kingston, Ontario
Alexander Kopp, BA;
Peter C. Austin, PhD
Institute for Clinical Evaluative Sciences
Toronto, Ontario
David N. Juurlink, MD, PhD
dnj{at}ices.on.ca
Sunnybrook and Women’s College Health Sciences Centre
University of Toronto
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Letters Section Editor: Robert M. Golub, MD, Senior Editor.
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