More employees are approaching their managers with concerns around mental health, but most companies fail to offer appropriate training, research suggests.
An Institute of Directors poll of 700 managers found four in 10 had been approached by staff with such a concern.
That was up from just over a quarter in 2017.
However, only 17% of firms offered mental health training for managers.
Two thirds did not offer such training, while 17% said it was not applicable or did not know.
The findings have been released to coincide with the start of Mental Health Awareness Week.
Poor relationships with line managers, along with workload, have the biggest negative impact on employees' mental health, the survey found - closely followed by poor relationship with colleagues.
Just over four in 10 respondents said some of their employees took time off work due to mental health problems.
Stephen Martin, director-general of the Institute of Directors, said directors needed to put as much importance on the mental health of their workforce as they would their physical health.
"The workplace shouldn't be somewhere that people feel they have to hide the problems they are facing. In fact, it should be one of the places where help is most easily found," he said.
"Larger organisations need to make sure that good practice spreads through every layer of their organisation. In smaller firms, where capacity for formal training is often limited, managers must still show willing to engage with the issue.
"We want businesses to see tackling mental health not as a drain on resources but as a positive investment in the wellbeing of their staff."
Most respondents to a separate survey of more than 500 managers by QBE Business Insurance said they wanted more training on how to deal with workers' mental health issues, with many saying they did not feel properly equipped.
Meanwhile, a survey of 2,000 people for Investors in People has found three in five believed their mental health had been negatively affected by their work, while only a third said their mental wellbeing was supported by their employer.
Investors in People chief executive Paul Devoy said lost productivity stemming from poor mental health could cost the economy almost £100bn a year.