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.