Homeless patients in psychiatric hospitals are a scarcely studied and there is lack of knowledge about factors associated with homelessness and in-patient treatment.

To determine the change over time in the number of homeless psychiatric in-patients and to examine factors associated with homelessness.

Retrospective data analysis of 1205 selected electronic patient files on psychiatric in-patient treatment in a university psychiatric hospital in Berlin, Germany. The rate of patients experiencing homelessness over a 13-year period (2008–2021) and the sociodemographic and clinical factors associated with homelessness are analysed over time.

Our study revealed a 15.1% increase in the rate of homeless psychiatric in-patients over the 13-year period. Of the whole sample, 69.3% people lived in secure private housing, 15.5% were homeless and 15.1% were housed in sociotherapeutic facilities. Homelessness was significantly associated with being male (OR = 1.76 (95% CI 1.12–2.76), born outside of Germany (OR = 2.22, 95% CI 1.47–3.34), lack of out-patient treatment (OR = 5.19, 95% CI 3.35–7.63), psychotic disorders (OR = 2.46, 95% CI 1.16–5.18), reaction to severe stress (OR = 4.19, 95% CI 1.71–10.24), personality disorders (OR = 4.98, 95% CI 1.92–12.91), drug dependency (OR = 3.47, 95% CI 1.5–8.0) and alcohol dependency (OR = 3.57, 95% CI 1.67–7.62).

The psychiatric care system is facing an increasing number of patients in precarious social situations. This should be considered in resource allocation planning in healthcare. Individual solutions for aftercare, along with supported housing, could counteract this trend.