Overall one in three workers said they wouldn't dare bring the subject up with senior staff for fear of being marginalised or losing their job.
Mental health disorders are on the increase, with women and young people particularly susceptible to anxiety and depression.
"We still hear examples of mental ill-health being used as a form of casual insult".
"We want to turn management's attention to this blind spot", he said, adding there is more stigma attached to the words mental health than there is wellbeing.
Employees aged 18 to 24 worry most about facing discrimination at work due to their mental health.
And according to a separate study, employees feel clear communication that mental health issues are a valid reason for sick leave would make for a more inclusive workplace. One in four worry about the harassment they would receive if they were to disclose a mental health concern.
Many previous studies have also shown how access to nature and green spaces can benefit health, with a 2015 study of U.S. adults findings that men in particular and those age 65 and above sleep better when they have access to nature, with better sleep linked to a lower risk of depression. "As a result many staff are having to work alone, making violent attacks more likely".
Just some of the employers who have taken ownership of mental health in their workplace and trained Mental Health First Aiders include Unilever, Siemens and WHSmith.
When it comes to physical versus mental health, 62 per cent of managers agreed taking time off due to physical illness or injury is treated more seriously in the workplace than taking time off to improve mental wellbeing.
FTSE 100 businesses that used the words "mental health" or "wellbeing" more than twice in their annual reports a year ago raked in up to three times more profit than those that didn't, researchers have found.
A 2016 study also found that those who valued time over money reported being happier, with using spare time on more meaningful activities such as volunteering for a charity also increasing happiness.
One in five people in the workplace experience a mental health condition, and while many employers are developing policies to support a healthy workforce, there is no shared vision for mental health in the workplace.
Helping others has been found to have both physical and mental health benefits, with a 2013 review of 40 academic papers by the UK's University of Exeter finding that volunteers rated their levels of depression as lower and their levels of well-being and life satisfaction as higher than non-volunteers.