What Poor Mental Health Costs a Company, and Where the Money Actually Goes

How much does poor mental health in the workplace cost employers?

A great deal, and most of it is invisible on a balance sheet. The World Health Organization estimates that about 12 billion working days are lost every year to depression and anxiety alone, at a cost of roughly US$1 trillion a year in lost productivity. At company level, Deloitte estimates that poor mental health costs UK employers around £51 billion a year, with the biggest share coming not from sick days but from people working while unwell.

Those headline numbers are real, but they are easy to misuse. This article explains where the costs come from, what the return-on-investment figures do and do not mean, and how to think about the cost inside your own company. I write as a clinical psychologist who also runs a business, so I care about both halves of that sentence.

Where do the costs come from?

Much of that cost starts long before anyone takes sick leave. Burnout that rest no longer fixes and moral injury are two of the quieter ways it builds up inside a team.

Most estimates split the cost of poor mental health at work into three buckets:

• Absence: sick days and longer leave.
• Presenteeism: people at work but not functioning fully because they are unwell.
• Turnover: people leaving, and the cost of replacing and onboarding them.

Deloitte's 2024 UK analysis is one of the few that breaks this down for employers. Its estimate, based on 2022-23 data:

The same pattern appears in US research. In a 2003 JAMA study of workers with depression, Stewart and colleagues found that 81% of the cost of lost productive time came from reduced performance while at work rather than from absence. Goetzel and colleagues (2004), looking at ten common health conditions, found that presenteeism costs were higher than medical costs in most cases.

The practical lesson for HR leaders is simple. If you only track absence, you will see the smallest part of the bill.

What about engagement?

Engagement and mental health are not the same thing, but they are related, and the numbers are often quoted together. Gallup's State of the Global Workplace 2026 report found that global employee engagement fell to 20% in 2025, its lowest level since 2020, and estimated that low engagement cost the world economy approximately US$10 trillion in lost productivity, or 9% of global GDP.

Treat that as a separate signal rather than a mental health cost. Disengagement can come from poor management, unclear goals or a bad fit, not only from distress. But the overlap matters: the WHO's ICD-11 describes burnout as resulting from chronic workplace stress that has not been successfully managed, and one of its three dimensions is increased mental distance from one's job, which is close to what engagement surveys pick up.

Is there a return on investing in mental health?

There is good evidence that treatment pays back at population level, and more mixed evidence for specific workplace programmes.

The most cited figure comes from a 2016 return-on-investment analysis in The Lancet Psychiatry led by Chisholm and colleagues at the WHO. Modelling 36 countries from 2016 to 2030, it estimated that scaling up treatment for depression and anxiety would cost US$147 billion and return benefit-to-cost ratios of 2.3 to 3.0 to 1 when only economic benefits are counted, and 3.3 to 5.7 to 1 when the value of improved health is included. The WHO summarised this as roughly US$4 back for every US$1 invested in better health and ability to work.

Two caveats are important. First, this is a model of national treatment scale-up, not of a workplace wellbeing budget. Second, it assumed a modest 5% improvement in ability to work and productivity as a result of treatment.

Deloitte's 2024 report, which reviewed published ROI studies of workplace interventions, estimated an average return of £4.70 for every £1 invested in employees' mental health and wellbeing, with early intervention and prevention producing the highest returns. That is an average across very different programmes. It does not mean any purchase labelled "wellbeing" will return almost five times its cost.

Why do headline numbers mislead decision-makers?

Because they answer a different question from the one a CFO is asking. "What does depression cost the global economy?" is not "What will this programme save us?" A few traps to avoid:

• Scaling global figures down to your headcount. Your workforce, industry and benefits are not the global average.
• Mixing engagement and mental health costs as if they were one number.
• Treating ROI averages as guarantees. A high average can hide programmes that returned nothing.
• Counting only what is easy. Absence is easy to measure; presenteeism and turnover are not, so they get left out.

How can you estimate the cost in your own company?

You will not get a precise figure, but you can get a defensible range.

1. Absence: pull sick-leave days and, where your system allows, any absences recorded as stress or mental health related.

2. Turnover: look at regretted leavers and exit-interview themes such as workload, burnout or management. Use your own replacement-cost assumptions.

3. Presenteeism: use a short, validated self-report productivity measure in an anonymous survey, or at least ask about energy, focus and workload.

4. Benefits data: ask your EAP and health providers for aggregate, anonymised trends.

5. Write down your assumptions. A range with clear assumptions is more credible than a single precise number nobody can reproduce.

What actually reduces the cost of poor mental health in the workplace?

The WHO's 2022 guidelines on mental health at work set out the main levers. They recommend organisational interventions that reduce psychosocial risks such as bullying and low job control, mental health training for managers, and individual interventions as one part of a wider programme. They are also honest that much of the evidence for organisational interventions is of very low quality, largely because complex workplace changes are hard to study.

A large UK study by William Fleming (Industrial Relations Journal, 2024), covering 46,336 workers in 233 organisations, found that participants in individual-level programmes such as resilience training, mindfulness and wellbeing apps appeared no better off on wellbeing measures than non-participants. The direction for employers is consistent: change the work, train the managers, and offer individual support alongside, not instead.

Where does Dzeny fit?

Dzeny is an AI-based mental wellbeing app, so it sits in the "individual support" part of that picture. It can give employees a private, always-available space to reflect, track stress and practise evidence-informed techniques, and it can make it easier to recognise when to seek professional help. It will not offset the cost of chronic overload or poor management. Used alongside organisational change, it can help people notice problems earlier, which is where most of the cost is avoided.

The bottom line

Poor mental health is expensive mainly through the costs you do not see: people working at reduced capacity and people leaving. The ROI evidence for treatment is strong at population level and more variable for workplace programmes. For a company, the best investment is the unglamorous one: workload, management quality and a culture where people can say they are struggling, supported by good individual tools.

⚠️ Important

This article is for informational purposes only and is not a substitute for professional medical, psychological or financial advice. If you or someone you know is in crisis in the US, call or text 988 (Suicide and Crisis Lifeline, 24/7). Elsewhere, contact your local emergency number.