Repetition of intentional drug overdose: a population-based study

Abstract

Context: Intentional overdose is a leading method of self-harm and suicide, and repeat attempts strongly predict eventual death by suicide.

Objectives: To determine the risk of recurrence after a first intentional overdose. Secondary objectives included characterization of the temporal course and potential predictors of repeat overdose, a strong risk factor for death from suicide.

Methods: Design: Population-based cohort study.

Setting: Ontario, Canada, from 1 April 2002 to 31 March 2013.

Participants: All Ontario residents presenting to an emergency department after a first intentional overdose.

Main outcome measures: The incidence and timing of recurrent overdose.

Results: We followed 81,675 patients discharged from hospital after a first intentional overdose. Overall, 13,903 (17.0%) returned with a repeat overdose after a median interval of 288 (inter-quartile range: 62 to 834) days. Of these, 4493 (5.5%) had multiple repeat episodes. Factors associated with repeat self-poisoning included psychiatric care in the preceding year (adjusted hazard ratio [aHR] 1.55; 95% confidence interval [CI] 1.50 to 1.61), alcohol dependence (aHR 1.41; 95% CI 1.35 to 1.46) and documented depression (aHR 1.39; 95% CI 1.34 to 1.44). Female sex, rural residence, lower socioeconomic status, ingestion of psychoactive drugs and younger age were also weakly associated with repeat overdose.

Discussion: Hospital presentation for repetition of intentional overdose is common, with recurrent episodes often far removed from the first. While several factors predict overdose repetition, none is particularly strong.

Conclusion: Secondary prevention initiatives should be implemented for all individuals who present to the emergency department and survive intentional overdose.

Keywords:

• Recidivism
• self-poisoning
• suicide

Acknowledgements

We thank Brogan Inc., Ottawa for use of their Drug Product and Therapeutic Class Database.

Disclosure statement

Simon Hollands had full access to all of the data (including statistical reports and tables) in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis. Dr. Juurlink is the study guarantor. The manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained. No other authors report any conflicts of interest.

Funding information

This study was supported by an Emerging Teams grant from the Canadian Institutes of Health Research (CIHR), The Canadian Drug Safety and Effectiveness Research Network (CDSERN), The Paediatric Consultants Partnership Research Grant, Hospital for Sick Children and the Institute for Clinical Evaluative Sciences (ICES), a non-profit research institute sponsored by the Ontario Ministry of Health and Long-Term Care (MOHLTC). The opinions, results and conclusions reported in this paper are those of the authors and are independent from the funding sources. No endorsement by ICES or the Ontario MOHLTC is intended or should be inferred. Muhammad M. Mamdani has served on advisory boards and/or received honoraria from Astra Zeneca, Bristol-Myers Squibb, Eli Lilly and Company, Glaxo Smith Kline, Hoffman La Roche, Novartis, Novo Nordisk and Pfizer. Gideon Koren has served as a consultant for Duchesnay Inc., Bayer Inc., and Novartis Inc.; no other relationships or activities that could appear to have influenced the submitted work.

Ethical approval

This study was approved by the Research Ethics Board of Sunnybrook Health Sciences Centre, Toronto, Ontario. The lead author (the manuscript's guarantor) affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.