Firms are being urged to do more to support workers with mental health issues after new research revealed that an increasing number of employees are suffering.
A survey of 2,000 workers showed that almost a third said they had experienced a mental health problem, compared with one in four during a similar study five years ago.
The Chartered Institute of Personnel and Development (CIPD) said companies should encourage a culture of openness as well as train managers to support workers.
Only two out of five workers said they would feel confident when it came to telling their boss about a mental health problem.
Rachel Suff, employment relations adviser at the CIPD, said: "With people's experiences of mental health problems at work on the increase, it's disappointing not to see more employers stepping up to address them.
"Mental health should get just as much attention, awareness and understanding as physical health, and employers have a responsibility to manage stress and mental health at work, making sure employees are aware of, and able to access, the support available to them."
Emma Mamo of mental health charity Mind, said: "It's clear that there's a high prevalence of mental health problems among employees.
"It's vital that employers also have good support in place for all staff, including those experiencing unmanageable stress or poor mental health.
"Employees need to be reassured that if they do put their hands up, they'll be met with understanding, and additional support if necessary.
"Creating mentally healthy workplaces needn't be difficult or expensive - often it's about putting in place small adjustments, such as regular communication and flexible working hours."