"The global mental health burden is staggering," the authors write. "Mental health disorders and stress are increasing in incidence and in detection all over the world, and inevitably, employers shoulder a large share of that burden."

As such, employers are not only expanding their health care program offerings, but more and more are also starting to address broader organizational factors "that play a critical role" in supporting mental health and emotional well-being, according to the report.

"Employers should be cognizant of the drivers of stress, such as financial insecurity, making sure to align provision with employee preferences," the authors write. "All employers should also focus on broader organizational factors such as creating an inclusive culture, reducing stigma, thinking about the work environment and policies that impact mental health."

The insurer survey also found that that globally, the cost of medical care is rising at a similar rate to previous years, a rate that remains relatively stable. The global medical trend is projected to increase 6.8 percent in 2020, slightly above this year's 6.7 percent increase. Similarly, the rate of increase in the U.S. medical trend is also relatively stable – projected to rise 7.2 percent in 2020, compared to this year's 7.9 percent.

In other regions, the European rate of increase will remain stable at 4.3 percent, and in Latin America medical costs are projected to decrease from 12.2 percent to 11.7 percent. The most dramatic rise is in the Middle East and Africa, where costs are expected to jump to 9.3 percent from 8.5 percent.

"Beyond these averages, each region has countries where health care policy, political instability or a combination of the two have conspired to significantly raise the projections," the authors write. "In Latin America, Venezuela is predicted to see a dramatic increase of 180 percent and so pushes the average higher, while the Middle East and Africa is the region seeing the most marked increases."

The survey also found that 70 percent of insurers say "new technology" is a principle external factor driving the increase in medical costs. The finding "speaks to insurers' darkest fears that the conditions covered by their policies can be treated more effectively with new technology but that this treatment is more expensive," the authors write.

When asked to cite the three most significant factors driving medical costs per person, 73 percent of insurers cite an overuse of care by practitioners offering too many services, while 66 percent believe insured members are the ones responsible for overusing care.

"Both patients and practitioners are seen by insurers as using too much care to no great effect," the authors write. "This balance between prudence and largesse is a hugely difficult one to strike for any insurer."

Read more: 

• 5 best, 5 worst states for mental health parity
• Addressing mental health in the workplace: What do employers need to know about EAPs?
• Employers' mental health strategies coming into the spotlight