Homelessness, psychiatric disorders, and risks of suicide and self-harm: a population-based cohort study

BACKGROUND: Homelessness is associated with adverse outcomes, but associations with suicide and self-harm require careful examination. We examined risks of suicidal behaviours in people experiencing homelessness compared with the general population, and the contribution of psychiatric disorders.

METHODS: Nationwide, register-based data on people living in Denmark between Jan 1, 1999, and Dec 31, 2020, born between 1945 and 2006 and aged 15-76 years, were analysed. Homelessness was measured as any homelessness or current homelessness and previous homelessness. Outcomes were first self-harm episode and death by suicide. We estimated adjusted mortality rate ratios (aMRRs) and adjusted incidence rate ratios (aIRRs) in Poisson regression and probabilities of outcomes. Analyses were stratified by sex and adjusted for sociodemographic factors and psychiatric disorders.

FINDINGS: Among 5 188 284 residents, 56 663 (1·1%) had at least one episode of homelessness, accounting for 570 986 person-years. Within 10 years of first homeless shelter contact, 1·3% (95% CI 1·2-1·4%) of males and 0·9% (0·7-1·0%) of females had died by suicide and 9·2% (8·9-9·6%) of males and 9·9% (9·4-10·5%) of females self-harmed. Homelessness was associated with an elevated rate of suicide (males aMRR 2·2 [2·0-2·4]; females 3·8 [3·2-4·5]) and self-harm (males 3·5 [3·4-3·6]; females 3·3 [3·1-3·5]) compared with no homelessness. Current homelessness compared with no homelessness was associated with elevated adjusted suicide rates (males 3·7 [3·1-4·5]; females 8·0 [5·5-11·6]), which were higher than for previous homelessness (males 2·0 [1·8-2·2]; females 3·4 [2·8-4·1]). Psychiatric disorders added further risk of suicidality among people experiencing homelessness compared with no psychiatric disorder and no homelessness (males 19·9 [18·1-22·0]; too few cases for females). Self-harm in people experiencing homelessness increased risk of dying by suicide (males 7·4 [6·5-8·5]; females 17·7 [14·4-21·7]).

INTERPRETATION: Individuals experiencing homelessness have elevated risks of self-harm and suicide, particularly those who are currently homeless. An episode of self-harm and psychiatric disorders are important indicators of suicide in this vulnerable group. Findings highlight a need for improving assessment and intervention.

FUNDING: Independent Research Fund Denmark and NIHR Oxford Health Biomedical Research Centre.