Table 1. Inclusion and exclusion criteria.

Inclusion Criteria	Definitions
Population	People experiencing homelessness and vulnerable housing, defined as: “An individual who lacks stable, permanent, appropriate housing, or may be without immediate prospect, means and ability of acquiring it. There are four physical living situations involved with homelessness: 1) Unsheltered; 2) Emergency sheltered; 3) Provisionally accommodated and, 4) At risk of homelessness, referring to people who are not homeless, but whose current economic and/or housing situation is precarious or does not meet public health and safety standards” [31]. We defined vulnerable housing as: “someone who lives in one’s own room or apartment but has unstable living arrangements, often resulting in frequent transitions between homelessness and vulnerable housing” [32]. We did not set any restrictions on the timeline of homelessness (e.g. current, lifetime, past year, etc.). If no studies specific to homeless populations were identified for a given intervention, we expanded our inclusion criteria to the general population who use substances.
Interventions	Supervised consumption facilities	Legally sanctioned facilities where people who use substances can consume pre-obtained substances under supervision [33]. There exist various terminologies for these facilities, including: supervised injection facilities (SIF), supervised consumption sites (SCS), medically supervised injection centres (MCIS), among others.
	Managed alcohol programs	Shelter, medical assistance, social services and the provision of regulated alcohol to help residents cope with severe alcohol use disorder [34]
	Pharmacological interventions for opioid use disorder	Opioid therapy medications including methadone, buprenorphine, diacetylmorphine, levo-α-acetylmethadol (LAAM) and naltrexone.
	Pharmacologic agents for reversal of opioid overdose	Opioid antagonist administered intravenously or intranasally, e.g. naloxone.
Comparison	No intervention, standard intervention, alternative intervention, treatment as usual.
Outcomes	1. Mortality: All-cause mortality and rates of suicide. 2. Morbidity: Having a disease or a symptom of disease. For example, prevalence or incidence of a communicable or non-communicable disease. Morbidity also refers to medical problems caused by a treatment. 3. Substance use: As measured by the number of days using alcohol or substance, the rate, and frequency of using alcohol or substances, number of days of abstinence from alcohol or substances or physical and mental consequences of using alcohol or substances. 4. Mental health: Any measures assessing psychological status and wellbeing, including but not limited to, psychological distress, self‐reported mental health status, or mental illness symptoms. 5. Access to care: Access to health care means having "the timely use of personal health services to achieve the best health outcomes" [35]. Access to health care consists of four components [36]: • Coverage: facilitates entry into the health care system. Uninsured people are less likely to receive medical care and more likely to have poor health status. • Services: Having a usual source of care is associated with adults receiving recommended screening and prevention services. • Timeliness: ability to provide health care when the need is recognized. • Workforce: capable, qualified, culturally competent providers. 6. Retention in treatment: The length of time clients remain in treatment.
Study design	Systematic review of quantitative or qualitative studies. Exclude all other study designs and review types.
Exclusion Criteria	Justifications
Reviews that focus on low- and middle-income countries	Due to the variability in access to resources and supports in comparison to that in a high-income country vary greatly. We feel that the settings are different and should be synthesized separately.
Reviews that focus on Indigenous populations	The analysis of the interventions tailored to this population will be covered by an Indigenous research group
Reviews which focus on incarcerated populations	Not generalizable to the non-incarcerated homeless population.
Reviews which exclusively report on interventions for detoxification	Abstinence-based approaches are outside of the scope of this review