The stigma surrounding mental health problems must be removed, according to a spokesman for the Mental Health Foundation.
Simon Loveland said British adults are more likely to develop mental health problems than their counterparts in other parts of the world.
And he said recent research revealed that the majority of employers would not consider giving a job to someone with a history of mental illness.
"The overriding reason for people’s difficulty with mental health issues is lack of awareness," he remarked, pointing out that anxiety and depression are the most common problems and are often brought on by stressful experiences or pressure at work.
Mr Loveland said that one in four British adults will experience at least one mental health problem during their lifetime.
For employers this means being on the look out for signs of stress and anxiety and taking steps to minimise the risk to their staff.
According to a report from the World Federation of Mental Health, 12 per cent of the global population are affected by mental disorders.