October 24, 2018

The beginning: systematic reviews in homelessness

Ciara Keenan

Right from the beginning the Centre for Homelessness Impact has been committed to ensuring that homelessness policy and practice should be informed by reliable evidence. The methodology that should be employed to produce this thorough, objective and authoritative summary of the evidence in relation to the effectiveness of a particular policy, programme or intervention targeted at homelessness, is a Systematic Review. The Centre has commissioned Campbell UK and Ireland based in Queen’s University Belfast, along with experts (from Heriot-Watt and Cardiff Universities) to produce these evidence summaries.

Why a Systematic Review?

Other types of narrative reviews of existing evidence are far from systematic or transparent in the methods they use. This leaves them open to accusations of being incomplete and missing important evidence, on the one hand, and possibly “cherry picking” studies and being biased on the other. Also, there are many policies, programmes and interventions out there that have a lot of face appeal and are widely accepted and implemented in the area of homelessness, and yet there is little actual evidence to support them. Moreover, and in some cases, some popular programmes may actually be causing harm. A Systematic Review coupled with Meta-Analysis allows the researchers to synthesise this evidence to draw robust conclusions regarding the effectiveness of the policy, programme or intervention in question, e.g. on issues such as Housing First, cost effectiveness and the impact of discharge programmes.

How do you conduct a systematic review?

A systematic review uses transparent methods for identifying all the available evidence internationally in a way that is systematic and transparent. The evidence is then assessed and filtered, so that only the highest quality and most robust evidence is considered. The hallmark of systematic reviews is that they seek to reduce bias at all stages of the review process. Reviews registered with organisations such as Campbell and Cochrane are particularly reliable, as all authors are required to adhere to the same high standards of conduct and reporting.

The stages in conducting a review are:

Define your question and ideally register your proposed review title with Campbell or similar

Specify and publish your proposed methodology in advance in the form of a protocol

Conduct a thorough search of the literature

Screen your search results against your pre-specified selection criteria to identify included studies

Appraise the quality of studies found

Synthesise the evidence, this is where meta-analysis may or may not come in

Publish and disseminate your review

Update the review as new evidence is produced.

Next steps

You will see from the stages outlined above that any systematic review should begin with a well formulated and answerable research question. A question that is clear, structured, and objective will also allow the reviewers to build a search strategy with reduced bias and helps to avoid missing potentially relevant studies. Many factors can drive the question a systematic review seek to answer such as; publication of new evidence on a topic, controversy around the effectiveness of a particular homelessness intervention, or as the Centre is doing, through the strategic use of a evidence and gap maps which identify where robust evidence is either dense or sparse in particular areas.

How can I get involved?

Researchers can sometimes overlook the end users of the evidence when it comes to formulating our review questions. The Centre for Homelessness Impact is committed to engaging the end users early in the research process, even before the formulation of the priority questions. This collaboration has started with the creation of an advisory board and will continue with a survey. To take part in this survey please email us at and sign up to the Centre for Homelessness Impacts newsletter to stay involved as the Systematic Reviews progress.

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