Clinically significant substance use and residential stability among homeless or vulnerably housed persons in Canada: a longitudinal cohort study.

Background: We examined clinically significant substance use among homeless or vulnerably housed persons in three Canadian cities and its association with residential stability over time using data from the Health and Housing in Transition study.

Methods: In 2009, 1190 homeless or vulnerably housed individuals were recruited in three Canadian cities and followed for 4 years. We collected information on housing and incarceration history, drug and alcohol use, having a primary care provider at baseline and annually for 4 years.