Risk of mortality after emergency department presentation for self-harm among children and adolescents in Wales: a population-based cohort study

Background Self-harm in childhood and adolescence is associated with substantial morbidity and premature mortality, particularly from suicide. We aimed to quantify the risk of cause-specific and all-cause mortality following emergency department (ED) presentations for self-harm. Methods In this retrospective population-based cohort study, we used anonymised, linked electronic health records from the Secure Anonymised Information Linkage (SAIL) Databank. We included children and adolescents aged 5–18 years who presented to EDs in Wales between 2008 and 2023. Individuals with at least one ED presentation for self-harm were assigned to the exposed group, and those with no recorded self-harm presentations formed the comparison group. Follow-up began at the index ED presentation and continued until death, possible emigration, or end of data availability. The primary outcome was suicide; secondary outcomes included accidental death, other causes of death, and all-cause mortality. Associations between self-harm and cause-specific mortality were estimated using Cox proportional hazards models adjusted for age and sex. Kaplan–Meier failure curves (1 − survival) were estimated separately for each cause of death. Findings Between 2008 and 2023, we identified 611,336 young people who presented to EDs, of whom 14,007 (2.3%) had at least one self-harm presentation. During follow-up, 1451 deaths were recorded. Mortality was higher among those presenting with self-harm compared with controls without self-harm presentations (114 [0.8%] vs 1337 [0.2%], adjusted hazards ratio [aHR] 3.1, 95% CI 2.6–3.8). Suicide risk was markedly elevated in the first year after presentation (aHR 13.4, 95% CI 4.7–38.0) and remained increased during follow-up (aHR 4.9, 95% CI 3.4–6.9). There was a similarly increased risk of accidental death within one year (aHR 13.9, 95% CI 6.2–31.1) and after one year (aHR 5.5, 95% CI 3.9–7.7). No clear association between self-harm and other causes of death was observed. Interpretation ED presentation for self-harm identifies young people at elevated risk of premature mortality. Preventive interventions should extend beyond suicide alone to address accidental deaths, particularly in the period immediately following presentation. Funding McGill Global Health Programs Fellowship; John Fell Fund; NIHR Oxford Health Biomedical Research Centre; Academy of Medical Sciences; UK Department for Business, Energy and Industrial Strategy.