Feeling insecure about your job harms both mental and physical health -- whether you actually lose your job or not. The toll taken by job insecurity can be as great as a serious or life-threatening illness, the study said.

Researchers analyzed information from more than 1,000 men and women, under age 60, who underwent two interviews, about three years apart. About 25 percent of the people in the study reported feeling insecure about their jobs in at least one of the two interviews.

People who said they felt insecure about their jobs had much lower self-rated health. They were about twice as likely to report physical health that was less than very good or excellent than workers who expressed feelings of job security at both interviews.

Private-sector workers were more vulnerable to the negative health effects of job insecurity than public-sector workers.

Job insecurity was especially hard on the well-being of black workers, the study found. Black workers who felt constantly insecure about their jobs were nearly three times as likely as insecure whites and more than four times as likely as secure whites to report very high levels of depressive symptoms.

The findings suggest that there may be worker health repercussions as the result of current trends in the U.S. labor market, such as outsourcing, downsizing and the increase in nonstandard jobs with reduced hours and benefits.

The study was to be presented April 1 at the annual meeting of the Population Association of America in Los Angeles.