Even as the Labor Department released figures showing that the economy lost more than half a million jobs in April, researchers on Friday made public a large study with an unsettling finding: losing your job may make you sick.

A researcher at the Harvard School of Public Health analyzed detailed employment and health data from 8,125 individuals surveyed in 1999, 2001 and 2003 by the Panel Study of Income Dynamics at the University of Michigan.

Workers who lost a job through no fault of their own, she found, were twice as likely to report developing a new ailment like high blood pressure, diabetes or heart disease over the next year and a half, compared with people who were continuously employed.

Interestingly, the risk was just as high for those who found new jobs quickly as it was for those who remained unemployed.

Though it has long been known that poor health and unemployment often go together, questions have lingered about whether unemployment leads to illness, or whether people in ill health are more likely to leave a job, be fired or be laid off.

In an effort to sort out this chicken-or-egg problem, the new study looked specifically at people who lost their jobs through no fault of their own — for example, because of a plant or business closing.

The author, Kate W. Strully, said she looked at situations in which people lost jobs for reasons that “shouldn’t have had anything to do with their health.”

What happens to their health afterward, then, “isn’t reflecting a prior condition,” said Dr. Strully, an assistant professor of sociology at the State University of New York at Albany, who did the research as a Robert Wood Johnson Foundation scholar at the Harvard School of Public Health.

Only 6 percent of people with steady jobs developed a new health condition during each survey period of about a year and a half, compared with 10 percent of those who had lost a job during the same period. It did not matter whether the laid-off workers had found new employment; they still had a 1 in 10 chance of developing a new health condition, Dr. Strully found.

David R. Williams, a professor at the Harvard School of Public Health who was not involved in the research, said the study was a reminder that job loss and other life stressors have a tremendous impact on mental and physical health and contribute to the development of chronic conditions.

“We know that stress affects health,” said Dr. Williams, who is director of the Robert Wood Johnson Foundation Commission to Build a Healthier America. “It causes changes in physiological function in multiple ways, and it can lead to alterations in health behavior. People no longer exercise; they eat more; they drink more. People who smoke, smoke more on high-stress days.”