Trends and socioeconomic inequalities in acute mental health service use in Canada, 2004-2019: a nationally representative retrospective cohort study.

BACKGROUND Acute mental health service use (AMHSU), that is, hospitalisations and emergency department (ED) visits for mental health, have been rising in the Canadian province of Ontario and globally; however, national-level estimates are not available. We examine trends and socioeconomic inequalities in AMHSU in the Canadian adult population between 2004 and 2019. METHODS Using the Canadian Community Health Survey linked to tax and health administrative datasets, we reported prevalence rates of AMHSU using negative binomial regression models. Income-based absolute inequalities in AMHSU were reported using the Slope Index of Inequality. RESULTS Over the study period, hospitalisations for mood disorders decreased from 144.8 (95% CI: 116.0-173.7) to 67.5 (95% CI: 54.5-80.4) per 100 000, while those for substance-related disorders (SRD) increased. Rates of ED visits increased for all conditions, with the largest increase for anxiety disorders, from 252.3 (95% CI: 210.9-293.6) to 434.1 (95% CI: 382.2-486.1) per 100 000. Females had higher rates of hospitalisations and ED visits for all conditions except SRD. We found pronounced income-based inequalities in both hospitalisations and ED visits for mental health, comparing those at the top versus bottom of the income distribution. Absolute inequalities for hospitalisations widened for SRD, from -93.6 (95% CI: -131.1 to -56.1) to -135.2 (95% CI: -203.4 to -67.1) per 100 000, and decreased for mood disorders, from -309.5 (95% CI: -443.8 to -175.3) to -126.0 (95% CI: -182.0 to -69.9) per 100 000. Additionally, absolute inequalities increased for ED visits across all mental health conditions. CONCLUSION Interventions aimed at improving access to preventive services could mitigate observed inequalities in AMHSU.