Identifying local interventions to address the adverse effects of household overcrowding on family wellbeing: a rapid realist review

Household overcrowding in England is a growing public health concern, exacerbated by poor housing quality and linked with mental health issues, higher risk of infectious diseases, injuries, and poorer educational outcomes. As affordable space becomes scarce, rehousing may not always be feasible. To explore alternative strategies, we conducted a rapid realist review of both peer-reviewed and grey literature, supplemented by stakeholder panels—including local authority staff (from London, Doncaster, Salford) and residents with lived experience in London boroughs. Our objective: identify effective interventions that local governments can use to alleviate the health harms caused by overcrowding.

• We identified 15 evaluated interventions internationally, grouped under Rehousing, Home improvements, and Coordination with healthcare and wider services.

• The UK-based literature was sparse. While studies showed reductions in overcrowding, fewer assessed health outcomes and those that did used inconsistent measures.

• Stakeholder perspectives and grey literature added crucial context, leading to important recommendations for policy and practice.

• Reducing overcrowding effectively requires national, long‑term investment in affordable housing stock—but this is unlikely to address short-term needs.

• Home improvements and enhanced healthcare coordination offer promising solutions to improve wellbeing for residents unable or unwilling to move. Although economic benefits are likely, further evaluation is needed.

• While our focus was urban England, our findings draw on international evidence, making them potentially transferable to similar global contexts.

To support knowledge translation, the project has been presented at multiple stakeholder events, including:

• Pan-London HDRC Advisory Board (September 2024)

• Tower Hamlets Housing Research Workshop (July 2024)

• Local Authority Public Health Research Network Conference (March 2024)

• Reducing Overcrowding Knowledge Share Session (October 2023)

We preregistered the review protocol via PROSPERO and uploaded a manuscript preprint to medRxiv. A peer‑reviewed journal paper is currently under review, and a book chapter for UCL Press is forthcoming. The findings are also being prepared for presentation at UCL’s Department of Primary Care & Population Health Seminar Series (December 2024), with the aim of informing local councils, including Tower Hamlets and Islington on practical interventions to protect health in overcrowded homes.

Islington Council

City of Doncaster Council

Tower Hamlets Council

Camden Council

Newham Council

Greater London Authority

Salford Council, Act Early

QMUL