Mental health issues are hitting younger employees harder than older ones, with 41 percent of those between 18 and 25 reporting being stressed at work "often or always." (Photo: Shutterstock)

A new study reveals that the stigma attached to mental health issues is costly—not just to employees struggling to achieve better medical outcomes, but also to their employers' bottom lines.

The international study on workplace mental health, conducted by Ipsos MORI and commissioned by Teladoc Health, finds that under-reporting by employees of mental health issues is wildly common—82 percent of those with a diagnosed mental health condition said they didn't tell bosses—and 10 percent of those said they feared losing their jobs if they disclosed the condition to someone at work.

Related: Employers' mental health strategies coming into the spotlight

"While society is generally promoting the conversation about mental health, the data show that employees don't want to and don't know how to talk about it at work," says Dr John Oldham, Professor of Psychiatry at Menninger Clinic. "Not surprisingly, stigma is the biggest obstacle in obtaining help for mental health problems."

Meanwhile, 38 percent said they kept the truth hidden lest it negatively affect their careers; 40 percent lied about the reason they used time off for mental health issues; 22 percent feared being thought less of professionally; 21 percent cited embarrassment and 17 percent figured their work capabilities would be called into question.

The issue is hitting younger employees harder than older ones, with 41 percent of those between 18 and 25 reporting being stressed at work "often or always," compared with 30 percent overall; 28 percent saying they "rarely or never" feel healthy, mentally and emotionally, compared with 16 percent overall; 61 percent saying mental health issues have affected their job performance, compared with 38 percent overall; and 66 percent saying they've actually missed work because of mental and emotional health issues, compared with 44 percent overall

A majority—55 percent—say not enough is being done in their workplace on mental health issues, with 43 percent citing lack of action on mental health awareness and 38 percent saying they'd be more productive at work if they had better mental health support.

"We've seen it first hand with our own global workforce," says Jason Gorevic, CEO, Teladoc Health. "Employees want leaders to lead, to set the dialogue in motion around mental health and normalize the conversation. For employers and employees alike, there is substantial health and economic value in getting individuals the right diagnosis, action plan and support needed to be well and productive in life and at work."