Outline of the Study

This report presents the third edition of the Centre for Homelessness Impact's Evidence and Gap Map (EGM). It documents evidence on interventions to improve outcomes for people experiencing, or at risk of homelessness, focusing on system reviews and impact evaluations. 

The map organises 394 studies (349 primary studies and 45 systematic reviews) into an interactive matrix, categorising interventions against measured outcomes. The new edition includes 134 additional studies and an expanded framework of 43 intervention sub-categories across 9 main categories. 

The EGM underpins the Intervention Tool and other digital tools created by CHI, to help policymakers and practitioners identify what works, highlight evidence gaps, and inform strategic investment in homelessness services.
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Findings in Brief
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• The evidence base has grown substantially, from 221 in the first edition (2018) to 394 studies ‍
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• 210/349 primary studies are randomised controlled trials (RCTs), demonstrating the feasibility of rigorous evaluation methods in the homelessness sector
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• The largest evidence concentrations relate to: services and outreach interventions (192 studies), health and social care interventions (164 studies), accommodation and accommodation-based services (145 studies)

• There are significant variations in evidence across intervention types: Housing First has 60 studies, whilst hostels have only one study included and reconnections programmes have none Substantial evidence gaps also exist around: legislation (3 studies), communication (2 studies), financing (1 study), prevention and employment interventions and cost-effectiveness
   
• Over 80% of studies (352) come from North America and only 28 studies are from the UK (13 systematic reviews and 15 are primary studies)
  
  
• Over 50% of primary studies have low confidence ratings, largely due to high attrition rates and absence of power calculations
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Recommendations in brief:
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• Invest in UK-based primary studies to test promising interventions in the UK context, drawing on learning from North American study methodology
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• Commission systematic reviews for key interventions in areas with many primary studies but no synthesis, particularly interventions beyond health and supported accommodation
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• Improve study quality through: including power calculations in study designs, improving methods to track participants and reduce attrition and reporting differential attrition between treatment and control groups

• Target research around interventions relating to legislation, homelessness prevention, employment support, communication strategies and cost-effectiveness data.

• Support organisations to undertake rigorous evaluations of their programmes, including RCTs where feasible and ethical
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• Continue with annual EGM updates, to capture emerging evidence, support commissioning of systematic reviews and update the intervention tool and to maintain its usefulness for strategic planning.

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