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.