Evidence supports the effectiveness of Housing First (HF) programs for people who are experiencing homelessness and mental illness; however, questions remain about its use in people with comorbid substance use disorders (SUD). The aim of this project was to test whether SUD modifies the effectiveness of an HF intervention. Secondary analysis of data from a randomized controlled trial of HF versus treatment-as-usual (TAU) with 24-month follow-up, comparing those with and without SUD at trial entry. The intervention studied was housing paired with Intensive Case Management or Assertive Community Treatment.

People with SUD in both the HF and TAU groups spent less time in stable housing, but the effect of HF did not vary by SUD status (OR=1.17, 95% CI = -0.77, 1.76). Likewise, there was no difference between those with and without SUD in the effect of HF (over TAU) on community functioning (b=0.75, 95% CI = -0.36, 1.87), quality of life (b=-1.27, 95% CI = -4.17, 1.63), health-related quality of life (b=-0.01, 95% CI = -0.03, 0.02), or mental health symptoms (b=0.43, 95% CI = -0.99, 1.86).

Housing First programs in Canada are equally effective in people with and without comorbid substance use disorder (SUD). Overall, the intervention appears to be able to engage people with SUD and is reasonably successful at housing them, without housing being contingent on abstinence or treatment.