Thirty-six percent of companies feel "very high" or "overwhelming" stress levels at work, and 49% said work stress rose since last year, according to a survey of 9,340 staffing buyers by Express Employment Professionals.

"I can't say we're surprised by the results," said Express CEO Robert Funk. "Coming out of the recession, employers are hesitant to hire full-time workers due to uncertainty of new banking, tax and healthcare regulations. As a result, staff members are working double-time in an attempt to keep up. But they are also in danger of burn out in a time when their employers need them most."

Small businesses felt the greatest stress level, according to the survey.

However, the company said that another survey of 15,070 companies found that 29% of firms planned to hire for commercial positions in the coming year, 19% planned to add administrative jobs and 12% planned to hire for engineering positions.