Fewer U.S. workers believed the economy was getting stronger -- 20% in July compared with 24% in June, according to the index's survey. And the number of workers who believe more jobs are available fell to 8% from 14% in June.

In addition, 59% of workers reported confidence in their current employer, down from 65% in June.

"It is no surprise that workers feel increased anxiety, given recent headlines suggesting that the economic recovery is slowing and unemployment levels remain high," said SFN President and CEO Roy Krause. "Despite these mixed reports, it should be noted that more workers indicate that they are likely to look for a new job in the next year. Additionally, the number of people planning a job change not only rose from last month, but has consistently remained near 40% despite the ebbs and flows of the economy."

The index's survey questioned 1,371 employed adults in the U.S.