Long-term outcomes following self-poisoning in adolescents: a population-based cohort study

Background Suicide is the third most common cause of death among adolescents worldwide, and poisoning is the leading method of attempted suicide. Unlike more violent methods, survival after self-poisoning is common, providing an opportunity for secondary prevention. We determined the risk and time course of completed suicide after adolescent self-poisoning, and explored potential risk factors. Methods We did a population-based cohort study using multiple linked health-care databases in Ontario, Canada, from Jan 1, 2001, to Dec 31, 2012. We identified all adolescents aged 10-19 years presenting to hospital after a first self-poisoning episode. Each was matched with 50 population-based reference individuals with no such history, matching on age, sex, and year of cohort entry. The primary outcome was the risk of suicide after a first self-poisoning episode. Secondary analyses explored factors associated with suicide and self-poisoning repetition. Findings We identified 20 471 adolescents discharged from hospital after a first self-poisoning episode and 1 023 487 matched reference individuals. Over a median follow-up of 7.2 years (IQR 4.2-9.7), 248 (1%) adolescents discharged after self-poisoning died, 126 (51%) of whom died by suicide. The risk of suicide at 1 year after self-poisoning was greatly increased relative to reference individuals (hazard ratio [HR] 32.1, 95% CI 23.6-43.6), corresponding to a suicide rate of 89.6 (95% CI 75.2-106.7) per 100 000 person-years over the course of follow-up. The median time from hospital discharge to suicide was 3.0 years (IQR 1.1-5.3). Factors associated with suicide included recurrent self-poisoning (adjusted HR 3.5, 95% CI 2.4-5.0), male sex (2.5, 1.8-3.6) and psychiatric care in the preceding year (1.7, 1.1-2.5). Adolescents admitted to hospital for self-poisoning were also more likely to die from accidents (5.2, 4.1-6.6) and from all causes (3.9, 2.8-5.4) during follow-up. Interpretation Self-poisoning in adolescence is a strong predictor of suicide and premature death in the ensuing decade, and identifies a high-risk group for targeted secondary prevention. Suicide risk is increased for many years after the index hospital admission, emphasising the importance of sustained prevention efforts.