title: Emergency department use and hospitalizations among homeless adults with substance dependence and mental disorders.
abstract: 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.
  
  
  BACKGROUND
  ISRCTN57595077 and ISRCTN66721740.
authors.affiliation: Department of Medicine, Centre for Health Evaluation and Outcome Sciences, University of British Columbia, 588B-1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada. adrienne.cheung@alumni.ubc.ca.
authors.forename: Adrienne
authors.initials: A
authors.lastname: Cheung
authors.affiliation: Faculty of Health Sciences, Simon Fraser University, Vancouver, Canada. jsomers@sfu.ca.
authors.forename: Julian M
authors.initials: JM
authors.lastname: Somers
authors.affiliation: Faculty of Health Sciences, Simon Fraser University, Vancouver, Canada. akm_moniruzzaman@sfu.ca.
authors.forename: Akm
authors.initials: A
authors.lastname: Moniruzzaman
authors.affiliation: Faculty of Health Sciences, Simon Fraser University, Vancouver, Canada. mlpatter@sfu.ca.
authors.forename: Michelle
authors.initials: M
authors.lastname: Patterson
authors.affiliation: School of Population and Public Health, Vancouver, Canada. jim.frankish@ubc.ca.
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Frankish
authors.affiliation: School of Population and Public Health, Vancouver, Canada. m.krausz@me.com.|Department of Psychiatry, University of British Columbia, Vancouver, Canada. m.krausz@me.com.
authors.forename: Michael
authors.initials: M
authors.lastname: Krausz
authors.affiliation: Department of Medicine, Centre for Health Evaluation and Outcome Sciences, University of British Columbia, 588B-1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada. apalepu@hivnet.ubc.ca.
authors.forename: Anita
authors.initials: A
authors.lastname: Palepu
mesh_terms: D000328:Adult; D001955:British Columbia; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D006703:Ill-Housed Persons / Q000706:statistics & numerical data*; D006760:Hospitalization / Q000706:statistics & numerical data*; D006786:Hospitals, Urban; D006801:Humans; D007198:Indians, North American / Q000706:statistics & numerical data; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology*; D008875:Middle Aged; D019966:Substance-Related Disorders / Q000453:epidemiology*