Methods	Designs: Cost analysis and randomised controlled trial
	Setting: Toronto, Montreal, Moncton, Winnipeg, Vancouver, Canada
	Follow up: up to 24 months
	Recruitment: Referred by health and social service agencies
	Randomization: Participants were randomized by a central data collection system that used an adaptive randomization algorithm
	Allocation: 1:1 allocation ratio
	Blinding: Not possible
	Timing of outcome assessment: At baseline and every six months for 21 or 24 months
	Outcome assessor: The investigators conducted in person interviews
Participants	Population: Homeless individuals or individuals living in a single room occupancy, rooming house, or hotel who have had two or more episodes of being absolutely homeless with serious mental illness and high support needs.
	Sample size: Total n = 950, Intervention n = 469, TAU n = 481
Interventions	Intervention:
	Housing First provides immediate access to independent housing and mental health supports; rent supplements were provided that ensured housing costs did not exceed 30% of participant's income; housing coordinators provided assistance to find and move into housing; support services were provided via assertive community treatment; study participants agreed to observe the terms of their lease and be available for a weekly visit by programme staff.
	Comparator:
	Treatment as usual (TAU): Participants had access to the already existing interventions and programs available in their community including any housing and community support other than the Housing First program
Outcomes	Housing stability, mental health, quality of life, substance use, hospital admission, employment, income
	Cost or cost‐effectiveness: The Housing First programme led to a reduction in the mean cost to $21,367 per person per year; this cost offset was associated with office visits, hospital admissions, emergency shelter visits, home visits, and incarceration; the savings gained by Housing First did not fully offset its cost.
Notes