TODAY is World Mental Health Day, a great time to invest in mental health at work; the perfect time for business to understand the facts, do the sums and be proactive.

The Health and Safety Executive says that, in 2014/15, stress accounted for 35 per cent of all work-related ill health cases while 43 per cent of all working days were lost due to ill health.

The employment dispute organisation, Acas, suggests that the cost of mental ill-health at work to UK employers is £30 billion a year.

The Centre for Mental Health estimates that mental health problems costs £1,035 for every employee each year in the UK.

When you combine these facts, you would think that every employer would make their employees’ mental health and wellbeing the priority; without people, there’s no business. As the founder of an online learning system designed to improve mental health and wellbeing in the workplace, Headtorch, I’ve visited many businesses, large and small, to discuss mental health at work.

When I start presentations I always ask: “Hands up if you’ve got mental health?” The immediate response is usually shuffling of feet, shifting of eyes and hands firmly clenched to thighs. Some people simply don’t know how to react.

The fact is that all of us have mental health, just as all of us have physical health and both can vary from day to day and week to week; that is normal.

The World Health Organisation describes health as “a state of complete physical, mental and social wellbeing and not merely the absence of disease or infirmity”.

Few us go through an entire year with absolutely no physical ailments. So why should it be surprising that our mental health is any different?

At work we need to recognise that our colleagues’ mental and social wellbeing needs support.

Research from the Chartered Institute of Personnel and Development (CIPD) on mental health at work states that almost half – 44 per cent – of employees would not feel confident disclosing unmanageable stress to their current employer. I uncovered similar views when carrying out research to develop Headtorch.

One of the questions I asked interviewees was: “What is the most common response to someone with mental health issues at work?”

The response was nearly always the same: people avoid talking about mental health in the workplace because they’re scared of opening a can of worms, one that they think they won’t be able to deal with.

The outcome is that nothing is done, often until the situation reaches crisis point.

Even then, the most likely response is panic – the manager runs to human resources for help.

If someone trips and breaks their leg or scuffs their toe at work, the accident book is completed. Yet when someone’s mood, behaviour and performance changes, what’s the protocol?

If there’s no support structure in place, then you’re more likely to hear comments about people needing to “pull their weight”, or “being moody” or seeming “withdrawn”.

Such responses create a culture that is closed and fearful. They promote stigma. They lead to unsupportive behaviours such as blame, bullying and isolation and create a perpetual negative cycle. Ultimately, this culture costs business talent, drive and reputation, all of which affect profit.

At work, I believe that we have an impact on our colleagues’ mental health and wellbeing and that everyone has a responsibility toward each other, regardless of where we are in the chain of command.

When the employer’s mindset is open, supportive and proactive, these behaviours are more likely to be reflected across the organisation.

Instead of running to human resources, the manager knows that having a supportive conversation, listening and showing empathy is not a scary thing. It means engagement and productivity go up and costs come down.

How much is mental ill-health costing your business? It’s worth doing your sums. That is because a mentally healthy workplace makes good business sense.

Amy McDonald is founder and chief executive of learning and development company Headtorch. Headtorch’s campaign marking World Mental Health Day: