RT Journal Article SR Electronic T1 Acute mental health service use following onset of the COVID-19 pandemic in Ontario, Canada: a trend analysis JF CMAJ Open JO CMAJ FD Canadian Medical Association SP E988 OP E997 DO 10.9778/cmajo.20210100 VO 9 IS 4 A1 Saunders, Natasha R. A1 Toulany, Alene A1 Deb, Bhumika A1 Strauss, Rachel A1 Vigod, Simone N. A1 Guttmann, Astrid A1 Chiu, Maria A1 Huang, Anjie A1 Fung, Kinwah A1 Chen, Simon A1 Kurdyak, Paul YR 2021 UL http://www.cmajopen.ca/content/9/4/E988.abstract AB Background: The extent to which heightened distress during the COVID-19 pandemic translated to increases in severe mental health outcomes is unknown. We examined trends in psychiatric presentations to acute care settings in the first 12 months after onset of the pandemic.Methods: This was a trends analysis of administrative population data in Ontario, Canada. We examined rates of hospitalizations and emergency department visits for mental health diagnoses overall and stratified by sex, age and diagnostic grouping (e.g., mood disorders, anxiety disorders, psychotic disorders), as well as visits for intentional self-injury for people aged 10 to 105 years, from January 2019 to March 2021. We used Joinpoint regression to identify significant inflection points after the onset of the pandemic in March 2020.Results: Among the 12 968 100 people included in our analysis, rates of mental health–related hospitalizations and emergency department visits declined immediately after the onset of the pandemic (peak overall decline of 30% [hospitalizations] and 37% [emergency department visits] compared to April 2019) and returned to near prepandemic levels by March 2021. Compared to April 2019, visits for intentional self-injury declined by 33% and remained below prepandemic levels until March 2021. We observed the largest declines in service use among adolescents aged 14 to 17 years (55% decline in hospitalizations, 58% decline in emergency department visits) and 10 to 13 years (56% decline in self-injury), and for those with substance-related disorders (33% decline in emergency department visits) and anxiety disorders (61% decline in hospitalizations).Interpretation: Contrary to expectations, the abrupt decline in acute mental health service use immediately after the onset of the pandemic and the return to near prepandemic levels that we observed suggest that changes and stressors in the first 12 months of the pandemic did not translate to increased service use. Continued surveillance of acute mental health service use is warranted.