Importance: Several factors may place people with mental health disorders, including substance use disorders, at increased risk of experiencing homelessness and experiencing homelessness may also increase the risk of developing mental health disorders. Meta-analyses examining the prevalence of mental health disorders among people experiencing homelessness globally are lacking.

Question: What is the prevalence of mental health disorders among people experiencing homelessness?

Findings: In this systematic review and meta-analysis, the prevalence of current and lifetime mental health disorders among people experiencing homelessness was high, with male individuals exhibiting a significantly higher lifetime prevalence of any mental health disorder compared to female individuals.

Meaning: These findings demonstrate that most people experiencing homelessness have mental health disorders, with current and lifetime prevalence generally much greater than that observed in general community samples.