Background: Peer support refers to a process whereby individuals with lived experience of a particular phenomenon provide support to others by explicitly drawing on their personal experience. It has been adopted in a variety of service contexts including homelessness, substance use, mental and physical health. Those who experience homelessness have some of the most complex intersecting health and social challenges. This ‘state of the art’ review provides a systematic search and synthesis of literature examining use of peer support models within services for people impacted by homelessness and problem substance use. Methods: A systematic search using six databases (CINAHL, SocINDEX, PsycINFO, MEDLINE, Scopus and Web of Knowledge) was conducted in August 2019 and identified 2248 papers published in English after the year 2000. After de-duplication and scanning titles/abstracts, 61 papers were deemed relevant. Three more papers (including one grey literature report) were identified via references, but two papers were later excluded due to relevance. The final 62 papers included studies conducted in five countries. A thematic analysis approach was used to compare and contrast the study findings and provide a synthesis of the main learning points. Results: In recent years there has been a substantial increase in research examining the utility of peer support yet there is significant variation across this field. Alongside profiling the range of settings, aims, populations, and main outcomes of these studies, this paper also provides an overview of overarching themes: the overall effectiveness and impact of peer-staffed or peer-led interventions; and challenges commonly faced in these roles. Five themes relating to the challenges faced by peers were identified: vulnerability, authenticity, boundaries, stigma, and lack of recognition. Conclusions: While our findings provide support for current efforts to involve individuals with lived experience in providing peer support to those experiencing concurrent problem substance use and homelessness, they also urge caution because of common pitfalls that can leave those providing the support vulnerable. We conclude that peers should be respected, valued, supported, and compensated for their work which is often profoundly challenging. Suggested guidelines for the implementation of peer involvement in research studies and service delivery are presented.

Overdose prevention for people who use illicit drugs is essential during the current overdose crisis. Peer support is a process whereby individuals with lived or living experience of a particular phenomenon provide support to others by explicitly drawing on these experiences. This review provides a systematic search and evidence synthesis of peer support within overdose prevention interventions for people who use illicit drugs. A systematic search of six databases (CINAHL, SocINDEX, PsycINFO, MEDLINE, Scopus, and Web of Knowledge) was conducted in November 2020 for papers published in English between 2000 and 2020. Following screening and full-text review, 46 papers met criteria and were included in this review. A thematic analysis approach was used to synthesize themes. Important findings include: the value of peers in creating trusted services; the diversity of peers’ roles; the implications of barriers on peer-involved overdose prevention interventions; and the stress and trauma experienced by peers. Peers play a pivotal role in overdose prevention interventions for people who use illicit drugs and are essential to the acceptability and feasibility of such services. However, peers face considerable challenges within their roles, including trauma and burnout. Future interventions must consider how to support and strengthen peer roles in overdose settings.

Background: People experiencing homelessness have higher rates of problematic substance use but difficulty engaging with treatment services. There is limited evidence regarding how problematic substance use treatment should be delivered for these individuals. Previous qualitative research has explored perceptions of effective treatment by people who are homeless, but these individual studies need to be synthesised to generate further practice-relevant insights from the perspective of this group. Methods: Meta-ethnography was conducted to synthesise research reporting views on substance use treatment by people experiencing homelessness. Studies were identified through systematic searching of electronic databases (CINAHL; Criminal Justice Abstracts; Health Source; MEDLINE; PsycINFO; SocINDEX; Scopus; and Web of Science) and websites and were quality appraised. Original participant quotes and author interpretations were extracted and coded thematically. Concepts identified were compared to determine similarities and differences between studies. Findings were translated (reciprocally and refutationally) across studies, enabling development of an original over-arching line-of-argument and conceptual model. Results: Twenty-three papers published since 2002 in three countries, involving 462 participants, were synthesised. Findings broadly related, through personal descriptions of, and views on, the particular intervention components considered effective to people experiencing homelessness. Participants of all types of interventions had a preference for harm reduction-oriented services. Participants considered treatment effective when it provided a facilitative service environment; compassionate and non-judgemental support; time; choices; and opportunities to (re)learn how to live. Interventions that were of longer duration and offered stability to service users were valued, especially by women. From the line-of-argument synthesis, a new model was developed highlighting critical components of effective substance use treatment from the service user’s perspective, including a service context of good relationships, with person-centred care and an understanding of the complexity of people’s lives. Conclusion: This is the first meta-ethnography to examine the components of effective problematic substance use treatment from the perspective of those experiencing homelessness. Critical components of effective problematic substance use treatment are highlighted. The way in which services and treatment are delivered is more important than the type of treatment provided. Substance use interventions should address these components, including prioritising good relationships between staff and those using services, person-centred approaches, and a genuine understanding of individuals’ complex lives.

Background: People who experience homelessness and those vulnerably housed experience disproportionately high rates of drug use and associated harms, yet barriers to services and support are common. We undertook a systematic ‘review of reviews’ to investigate the effects of interventions for this population on substance use, housing, and related outcomes, as well as on treatment engagement, retention and successful completion. Methods and findings: We searched ten electronic databases from inception to October 2020 for reviews and syntheses, conducted a grey literature search, and hand searched reference lists of included studies. We selected reviews that synthesised evidence on any type of treatment or intervention that reported substance use outcomes for people who reported being homeless. We appraised the quality of included reviews using the Joanna Briggs Institute Critical Appraisal Checklist for Systematic Reviews and Research Syntheses and the Scale for the Assessment of Narrative Review Articles. Our search identified 843 citations, and 25 reviews met the inclusion criteria. Regarding substance use outcomes, there was evidence that harm reduction approaches lead to decreases in drug-related risk behaviour and fatal overdoses, and reduce mortality, morbidity, and substance use. Case management interventions were significantly better than treatment as usual in reducing substance use among people who are homeless. The evidence indicates that Housing First does not lead to significant changes in substance use. Evidence regarding housing and other outcomes is mixed. Conclusions: People who are homeless and use drugs experience many barriers to accessing healthcare and treatment. Evidence regarding interventions designed specifically for this population is limited, but harm reduction and case management approaches can lead to improvements in substance use outcomes, whilst some housing interventions improve housing outcomes and may provide more stability. More research is needed regarding optimal treatment length as well as qualitative insights from people experiencing or at risk of homelessness.

With growing strain on mental health services, greenspace interventions could be a promising addition to current health and social care provisions as they have the potential to be widely accessible for people within their own communities and used alongside a variety of treatment plans. Despite promising progress in greenspace research, the underlying mechanisms and processes of greenspace interventions are still unclear. Without knowing these it is impossible to understand why programmes work and how best to replicate them. To address this gap this review uses realist methodology to synthesise the international evidence for greenspace interventions for mental health in both clinical and non-clinical populations. Forty-nine full text articles are included in the review and the underlying contexts, mechanisms, and outcomes of the interventions identified and refined into an original overriding theory under three themes of Nature, Individual Self, and Social Self. The interaction of these three factors represents a new conceptual framework for greenspace interventions for mental health and shows what works, for whom, and in what circumstances. The findings of this review are not only theoretically novel but they also have practical relevance for those designing such interventions including the provision of recommendations on how to optimise, tailor and implement existing interventions.

Background: The COVID-19 pandemic has necessitated unprecedented changes in the way that services are delivered to individuals experiencing homelessness and problem substance use. Protecting those at high risk of infection/transmission, whilst addressing the multiple health and social needs of this group, is of utmost importance. The aim of this novel qualitative study was to document how one service in Scotland, the Wellbeing Centre run by The Salvation Army, adapted in response.Methods: Care was taken to identify methods that did not create additional stress at this pressured time. Semi-structured interviews were conducted with Centre clients (n = 10, in-person and telephone) and staff (n = 5, telephone), and external professionals (n = 5, telephone), during April–August 2020. These were audio-recorded, fully transcribed, and analysed using Framework. Service documents were used to enhance contextual understanding. Analysis was informed by theories of psychologically informed environments and enabling environments.Results: The start of the pandemic was a time of confusion, disruption, and isolation. Centre staff rapidly adapted methods of engagement to provide a range of comprehensive physical and emotional supports, to both existing and new clients, through telephone and online communication and, eventually, socially distanced in-person support. This involved balancing the risks of COVID-19 infection/transmission with the benefits of continuity of support to those highly vulnerable to a range of harms. Whilst the pandemic created many challenges, it also facilitated removal of barriers, particularly concerning provision of harm reduction services which had previously been severely constrained. Clients described the Centre as a ‘lifeline’, providing stability and safety during a period of profound disruption when other services closed their doors. Strong leadership, intensive team working, support/training for staff, a focus on relationships, and active use of client feedback, enabled responsive adaptation to fast-changing demands and the creation of a ‘culture of care’.Conclusion: This study provides a unique insight into the pandemic by analysing the response of one homeless service during the height of the pandemic. We present a range of implications that have international relevance for those designing policies, and adapting front-line services, to proactively respond to COVID-19 and the continued public health crises of homelessness and drug-related deaths.