Employees fear their career prospects will be jeopardised if they admit they have mental health problems, according to a survey by disability insurer UnumProvident.
When asked whether they believed admitting they suffered from mental health problems, such as stress, depression and anxiety, would damage their careers, 77% of employees said yes, with older workers particularly concerned.
On a regional basis, the North West had the highest number of level of concern over the mental health issues, with 83% wary of discussing the subject.
The majority of respondents across the UK also believed that admitting to mental health problems would affect their employability, employer references pay and benefits.
Joanne Hindle, corporate services director of UnumProvident, said: "Company directors badly under-estimate the likely incidence of mental ill health among employees and colleagues and the implications for their business.
"Around three in every 10 employees will experience stress, depression or some other form of mental ill health in any year."
A recent survey by the Shaw Trust mental health charity found that 63% of employers believed their company policy on mental health was effective in helping their staff stay in work.
However, if employees do not reporting mental health problems for fear of repercussions on their career, Hindle said, then employers were less likely to be able to provide effective support.
"The taboo of mental ill-health needs to be broken so that employees and employers can pinpoint problems at the outset," she said.
"Early intervention is the key to rehabilitation in mental as well as physical ill-health and will maximise the chances of employees maintaining their careers and staying in work," Hindle added.