Programmatic, Environmental, and Temporal Predictors of Violence, Overdose, and Self-Injury in Homeless Shelters in Toronto, Canada, 2012-2021.

People experiencing homelessness have high rates of violent victimization, overdose, suicidality, and non-suicidal self-injury. These health-related critical incidents contribute to high mortality rates among homeless populations, making their prevention a critical public health goal. The objective of this study was to identify trends and correlates of physical violence, overdose, and self-injury in homeless shelters in Toronto, Canada. A retrospective study was conducted using administrative data on health-related critical incidents in Toronto's shelter system from 2012 to 2021. Log-linked negative binomial regression models were fitted to (a) predict physical violence, overdose, and self-injury incident counts during the study period by year, season, and pandemic onset, and (b) examine programmatic, environmental, and temporal correlates of these outcomes, with separate analyses performed for the pre-pandemic and pandemic periods. Shelter-based physical violence (incidence rate ratio [IRR] 1.08; 95% confidence interval [CI] 1.06-1.11), overdose (IRR 1.20; CI 1.13-1.26), and self-injury (IRR 1.16; CI 1.11-1.21) incidents increased over the study period, with the rates of the increases for violence (IRR 1.10; CI 1.00-1.20) and overdoses (IRR 1.66; CI 1.48-1.86) intensifying during the COVID-19 pandemic. Larger congregate shelters had higher rates of violence, overdose, and self-injury, whereas shelter-based hotels had lower incident rates. Critical incidents were also higher during the winter, and there was an increased rate of overdoses during cheque week. The development of smaller shelters that offer greater privacy to service users warrants further examination to advance safety in shelter settings. Increasing access to naloxone and other substance use supports, especially during check week, is also recommended for reducing drug-related harms.