Emergency department use and hospitalizations among homeless adults with substance dependence and mental disorders

BACKGROUND Homelessness, substance use, and mental disorders each have been associated with higher rates of emergency department (ED) use and hospitalization. We sought to understand the correlation between ED use, hospital admission, and substance dependence among homeless individuals with concurrent mental illness who participated in a 'Housing First' (HF) intervention trial. METHODS The Vancouver At Home study consisted of two randomized controlled trials addressing homeless individuals with mental disorders who have "high" or "moderate" levels of need. Substance dependence was determined at baseline prior to randomization, using the Mini International Neuropsychiatric Interview diagnostic tool, version 6.0. To assess health service use, we reviewed the number of ED visits and the number of hospital admissions based on administrative data for six urban hospitals. Negative binomial regression modeling was used to test the independent association between substance dependence and health service use (ED use and hospitalization), adjusting for HF intervention, age, gender, ethnicity, education, duration of lifetime homelessness, mental disorders, chronic health conditions, and other variables that were selected a priori to be potentially associated with use of ED services and hospital admission. RESULTS Of the 497 homeless adults with mental disorders who were recruited, we included 381 participants in our analyses who had at least 1 year of follow-up and had a personal health number that could be linked to administrative health data. Of this group, 59% (n = 223) met criteria for substance dependence. We found no independent association between substance dependence and ED visits or hospital admissions [rate ratio (RR) = 0.85; 95% CI 0.62-1.17 and RR = 1.21; 95% CI 0.83-1.77, respectively]. The most responsible diagnoses (defined as the diagnosis that accounts for the length of stay) for hospital admissions were schizo-affective disorder, schizophrenia-related disorder, or bipolar affective disorder; collectively reported in 48% (n = 263) of admissions. Fifteen percent (n = 84) of hospital admissions listed substance dependence as the most responsible diagnosis. CONCLUSIONS Substance dependence was not independently associated with ED use or hospital admission among homeless adults with mental disorders participating in an HF trial. Hospital admissions among this cohort were primarily associated with severe mental disorders. TRIAL REGISTRATION ISRCTN57595077 and ISRCTN66721740.