Homelessness is making people ill and it’s costing lives.  People without a secure home - those who are sofa surfing, living in temporary accommodation or sleeping on the streets - are more likely to suffer from depression, anxiety, chronic illness and addiction. They are more likely to miss GP appointments, disengage from treatment and end up in A&E. In short, homelessness  is a public health emergency. 

After decades working in public health, I believe there are important lessons the homeless sector can take from it - and prevention is one of the most vital. My early years as a doctor taught me that acting early can change lives. I’ve seen first-hand what happens when we ignore the warning signs -  and what’s possible when we intervene early with the right evidence.

Smoking is perhaps the best example in modern Britain of how powerful prevention can be. Since the 1970s, smoking rates have more than halved. That didn’t happen because millions of smokers simply decided to make healthier choices. It happened because we changed the environment. We  taxed tobacco, banned advertising, added graphic warnings to packets, banned smoking in public spaces and made it less socially acceptable. 

In healthcare, we don’t wait until someone collapses to intervene -  at least, not if we can help it. We screen for cancer before it spreads. We vaccinate to prevent diseases before they take hold. We monitor blood pressure and cholesterol to reduce the risk of stroke and heart attacks. We run smoking cessation programmes, offer diabetes prevention courses and build mental health support into primary care. We know that investing upstream reaps benefits later on.

But when it comes to homelessness, we too often do the opposite. We wait until someone is evicted, rough sleeping or in crisis before we act,  by which point the harm is greater, the costs are higher and the road back is far harder.

Just as we wouldn’t ignore the early signs of chronic illness in healthcare, we shouldn’t ignore the early warning signs of housing instability.  Rent arrears, domestic abuse, benefit delays, poor mental health, missed school, missed work -  these are the red flags that should trigger support. Effective interventions might include targeted financial support, legal advice on tenancy issues, family mediation,or short-term assistance for someone leaving hospital, prison or the care system.

We need genuine cross-system coordination to tackle homelessness — and the health sector has a critical role to play. It can do much more to contribute to the protective scaffolding that prevents homelessness by identifying risk earlier and working closely with housing, justice and education. For instance, it should become standard practice for GPs and other frontline clinicians to ask about housing when patients present with warning signs such as poor mental health, substance use or frequent A&E visits. By spotting these signs, acting early and referring people to the right services, doctors can reduce the chances of someone becoming homeless  and help prevent the crisis before it begins.

The move from crisis to prevention is key, and  that shift depends on robust evidence. We need to understand what works, for whom and under what conditions. That means better data, sharper indicators and tailored support for those most at risk, including young people leaving care, women fleeing domestic abuse, and people leaving prison. Most of all, we need a systematic way to identify and support them before they fall through the cracks.

That’s why I’m so pleased to have become Chair of the Centre for Homelessness Impact (CHI) -  an organisation dedicated to building the evidence base that homelessness prevention so urgently needs, and to putting that knowledge into the hands of those shaping policy across the country.

Policymakers are rightly cautious about “spend-to-save” arguments. With tight budgets and short political cycles, they want rock-solid evidence that early intervention delivers results  and saves money. If we want homelessness prevention to attract serious investment, we need to build a case they simply can’t ignore.

We also need to shift public perception. Many people still view homelessness as the result of poor personal choices when, for the vast majority, that simply isn’t true. But we’ve seen with smoking that public attitudes can change. Once the smell of smoke became socially unacceptable - in restaurants, on clothes, in public spaces -  it became easier for politicians to act. We need the same shift around homelessness so that people feel able to ask for help, not ashamed to need it.

The Government’s upcoming homelessness strategy presents an opportunity to make real, lasting change. As Chair of CHI, I see my role as helping ensure that national strategies are grounded in evidence, and that prevention is no longer an afterthought.

To treat homelessness as a public health issue is not to stretch the definition,  it’s to reflect the reality. Poor housing and housing insecurity directly harm people’s health. And better health, in turn, helps people sustain work, relationships and stable housing. The connections are clear. Now we need action to match the evidence.

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Professor Dame Carol Black is Chair of the Centre for Homelessness Impact

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