Comparison of Self-harm or Overdose Among Adolescents and Young Adults Before vs During the COVID-19 Pandemic in Ontario

IMPORTANCE Self-harm and deaths among adolescents and young adults are notably related to drug poisonings and suicide. With the emergence of the COVID-19 pandemic, there are projections about a greater likelihood of such events arising among adolescents and young adults. OBJECTIVE To evaluate the risk of self-harm, overdose, and all-cause mortality among adolescents and young adults during the COVID-19 pandemic. DESIGN, SETTING, AND PARTICIPANTS This population-based cohort study took place in Ontario, Canada, where a universal health care system captures all emergency department (ED) visits, hospitalizations, and deaths. The participants included all adolescents and young adults born in Ontario between 1990 and 2006, who were aged 14 to 24 years between March 1, 2018, and June 30, 2021. EXPOSURES The COVID-19 pandemic era (April 1, 2020 to June 30, 2021), relative to the 2 years preceding the pandemic (March 1, 2018 to February 28, 2020). MAIN OUTCOMES AND MEASURES ED encounters or hospitalizations for self-harm or overdose. A secondary outcome was self-harm, overdose, or all-cause mortality. Cause-specific hazard models to estimate hazard ratios (HR) and 95% CIs were used for the primary outcome. Follow-up started at March 1, 2018, or the individual's 14th birthday, whichever was later, and age was used as the time scale. RESULTS In this study, 1 690 733 adolescents and young adults (823 904 [51.3%] female participants) were included with a median (IQR) age of 17.7 (14.1-21.4) years at start of follow-up. After 4 110 903 person-years of follow-up, 6224 adolescents and young adults experienced the primary outcome of self-harm or overdose during the pandemic (39.7 per 10 000 person-years) vs 12 970 (51.0 per 10 000 person-years) prepandemic, with an HR of 0.78 (95% CI, 0.75-0.80). The risk of self-harm, overdose, or death was also lower during than before the pandemic (HR, 0.78; 95% CI, 0.76-0.81), but not all-cause mortality (HR, 0.95; 95% CI, 0.86-1.05). CONCLUSIONS AND RELEVANCE Among adolescents and young adults, the initial 15-month period of the COVID-19 pandemic was associated with a relative decline in hospital care for self-harm or overdose.