In the still, lonely hours before dawn, Karen Gaebelein sits in her living room chair staring out the window at the dark sky—her thoughts racing, heart pounding. At age 56, Gaebelein, who lives in Broadview Heights, Ohio, is worried about the mortgage on her condo, her shrinking retirement savings, her questionable job future.

Like millions of Americans, she is anxious, stressed by the troubling uncertainties of the faltering economy. And that stress is literally making her sick. Gaebelein, who has been unemployed for a year, has had trouble sleeping. Her blood pressure is high. She has bouts of depression. “I forget to eat some days,” says Gaebelein, who managed two offices of a credit union. “But once in a while I get a big bag of greasy fast food and a giant Hershey bar. I know I shouldn’t, I know it’s bad for me, but I can’t help it.”

While a certain amount of stress can increase productivity and creativity, too much can be mentally and physically damaging. Not only does stress provoke negative behaviors such as bingeing on junk food, smoking and excessive drinking, it can also lead to ailments ranging from colds and flu to depression, high blood pressure and memory loss.

Stress that persists over the years can exacerbate conditions such as heart disease, hardening of the arteries, autoimmune disease, diabetes and ulcers, experts say. Research indicates stress can also speed the aging process.

“Stress rarely causes disease, but it creates conditions that make the body more vulnerable to disease. And if you’re already sick or have a chronic illness, stress can make it worse,” says Sheldon Cohen, a psychologist at Carnegie Mellon University in Pittsburgh. “Its effects ... can be long-lasting.”

Stress, he says, “is the perception that you are facing demands that exceed your ability to cope.” The demands can be physical—say, if you’re being pursued by a robber. Or they can be psychological—worrying about a job or money.

Today’s economic meltdown is triggering widespread psychological stress, which feeds on uncertainty and dread. “We feel our control slipping and our lives growing more and more unpredictable,” says Cohen. And the mind repeatedly mulls the same questions: What will happen next? How long will it go on? Will it get worse?

Americans of all ages are living with the anxieties that a troubled economy brings. But some of the most stressed people, like Gaebelein, have been laid off in their last decade of work, with less chance of finding a new job and recouping financial losses.

“Losing your job at 50 or 60 is not good for your health,” says William Gallo, a research scientist at Yale University’s School of Medicine in New Haven. “There is compelling evidence that no matter who you compare the older job loser to, he or she does worse physically and mentally.”

Gallo’s studies, which tracked older people who lost their jobs after a plant closing, found not only that they had more symptoms of depression, but also that “their risk of heart attack and stroke was more than doubled compared with people who did not lose their jobs.”

Gallo says that job loss for people age 50 and older—with its attendant anxiety—should be considered an added risk factor for cardiovascular problems. (When study participants found other jobs, he says, the risk was greatly reduced.)

Another finding: People who fear losing their jobs have more health problems than those who actually lost them, says Sarah A. Burgard, assistant professor of sociology at the University of Michigan. She and her team looked at 3,000 employed people under age 60 participating in two long-term studies and divided them into those who worried about losing their jobs and those who didn’t. They found that over a two-year period people who felt chronically insecure about their jobs reported much worse overall health and were more depressed than those who actually lost their jobs.

“Living with uncertainty, that’s extremely damaging to your health,” says Burgard.