Think the health disparities between rich and poor are simply a matter of unequal access to health care? Think again.

Health disparities exist in the United Kingdom and other countries with universal health coverage that should flatten differences. Disparities exist even in the upper brackets, with Americans who make $500,000 a year enjoying fewer health problems and longer lives than those making a still-hefty $100,000 a year.

"As you move up the socioeconomic status hierarchy, your health prospects continue to improve," says psychologist Norman B. Anderson, PhD, a professor of health and social behavior at Harvard University's School of Public Health and former director of the Office of Behavioral and Social Sciences Research at the National Institutes of Health (NIH). "Why that happens is the $100,000 question."

Now psychologists are working to find the answer. Using new methodological strategies, they're trying to figure out how a constellation of economic, social and work factors--together known as socioeconomic status--affects health. They're exploring ways to mitigate low status's negative effects. And they're hoping to convince policy-makers and others that low status is not only an economic problem but a health risk, too.

Linking status and health

Epidemiological studies have confirmed the relationship between income, education and occupation on the one hand and health outcomes on the other. The decade-long Whitehall study of 17,350 British civil servants, for example, found that relative risk of death increased significantly as rank decreased. The message is simple: The lower your socioeconomic status, the greater your risk of both physical and psychological health problems.

Now psychologists are trying to find out why. Behavioral and environmental differences clearly play a role, since those at the lower end of the socioeconomic spectrum tend to smoke more, eat worse and live in unhealthier environments. But something more seems to be at work as well. The hypothesis? Inequality itself contributes to health disparities.

"One of the greatest advances of the last few years has been that socio-economic status is now viewed as a determinant of health rather than a mere correlate," says Anderson.

Instead of controlling for socioeconomic status, researchers are beginning to study it as an etiologic factor in its own right. Nancy E. Adler, PhD, for instance, has developed a new measure of subjective social status. Adler, a professor of medical psychology at the department of psychiatry and the Center for Health and Community at the University of California at San Francisco, asks people to identify their place on a socioeconomic ladder.

Not surprisingly, says Adler, people's self-reported status turns out to be correlated to objective indicators such as income and education. But, she says, their self-reported status is even more highly correlated with biological and psychological health outcomes.

In one study, for example, Adler collected objective data about women's socioeconomic status and then asked them on which rung of the socioeconomic ladder they felt they belonged. She found that the women's subjective assessments were more consistently and strongly related to health factors, such as self-rated health, heart rate, sleep quality, body fat distribution and cortisol habituation to repeated stress, than the objective assessments.

Sheldon Cohen, PhD, a professor of psychology at Carnegie Mellon University in Pittsburgh, has used the socioeconomic ladder concept to study the impact socioeconomic status has on the immune system's ability to ward off infections.

Cohen's interest grew out of a study of stress and susceptibility to upper-respiratory infection among monkeys. Although stress had no effect on the monkeys' susceptibility to the virus researchers exposed them to, it turned out that their position in the monkey hierarchy did. The more subordinate the monkey, the more likely it was to succumb to the virus.

Intrigued, Cohen began studying the relationship between humans' perceived social status and their susceptibility to infection. Participants in these studies mark a rung on a picture of a ladder to show where they think they are in terms of their community and their country. People who put themselves on a low status rung were at very high risk of developing infections.

"One of the reasons we use the ladder is because standard measures of socioeconomic status, such as education, income and occupation, miss a lot," Cohen explains. "Think of someone who doesn't have much education, much income or a good job but is a deacon in a church. That person may have fairly high status in the community even though he would come out as low status through traditional measures."

Cohen has also taken a closer look at specific markers of social status. In one study, for instance, he found that people who were underemployed or unemployed were four and a half times more likely than other participants to get sick when exposed to the cold virus.

Getting 'under the skin'

Other researchers have zeroed in on the fact that members of ethnic and racial minorities are more likely than whites to have low socioeconomic status. To take just one indicator of socioeconomic status, the U.S. Census Bureau reports that 1999 poverty rates were 26 percent for American Indians and Alaska Natives, 24 percent for African Americans, 23 percent for Hispanics and 11 percent for Asians and Pacific Islanders, compared to just 8 percent for whites.

Hector F. Myers, PhD, a professor of psychology at the University of California at Los Angeles, believes that racism increases the vulnerability of those already struggling with low socioeconomic status. Myers has studied the ways that racism-related stress gets "under the skin" to affect the health of racial and ethnic minorities.

"We've often chosen to focus on either ethnicity or class rather than on the interaction between the two," says Myers. "We've become a lot more sophisticated in our thinking recently."

According to Myers, racism affects people's health through both psychological and biological pathways. From a psychological standpoint, he says, racism has a demoralizing effect that can undermine health and well- being. And it's not just overt racism that renders people vulnerable, he says. Even more debilitating are ambiguous incidents that leave people wondering what really happened.

These psychological effects then interact with biological processes, says Myers, noting that anger, self-doubt and other emotions may result in hemodynamic, endocrinological, immunological and other changes that lead to disease.

"I'm not suggesting that exposure to a racist event necessarily leads to hypertension," Myers explains, noting that the process is much more insidious. "Instead it builds on existing biological vulnerabilities people might have."

A person with a family history of high blood pressure is already at risk of developing hypertension, Myers points out. The stress of racism may add to what Myers calls "cumulative vulnerability" and that person's chances of succumbing to disease. Myers is planning to investigate whether chronic exposure to racism even contributes to genetic mutations that increase vulnerability.

Treating 'socioeconomic stress'

Other psychologists are exploring ways to treat people suffering from status-related stressors that may ultimately lead to physical problems. Lauren E. Storck, PhD, a private practitioner in Belmont, Mass., and a clinical instructor in the psychiatry department at Harvard Medical School, is exploring ways to treat what she calls "socioeconomic stress syndrome."

"This is a psychosocial syndrome that combines features of depression and anxiety along with a dissociative-like process," she says, explaining that her theory is based on narrative data she and other researchers have collected. "It's due to socioeconomic insults or injuries that have not had a chance to be exposed, digested or talked about in a healing place."

In our supposedly classless society, Storck says, people find it difficult to talk about class. As a result, people at both ends of the socioeconomic spectrum can express class-related traumas only through psychological or psychomedical complaints. Whether it's a new immigrant facing poverty and discrimination or a recent widow facing a plummeting income, says Storck, people need to be able to talk about these emotional wounds. It is crucial not to blame the individual and to recognize this is a complex societal issue.

Storck is trying to help people do just that. In addition to teaching and working with patients, she is planning research that uses small and large group dynamics to help participants overcome socioeconomic stress.

On a broader scale, NIH has issued a call to eliminate health disparities. This NIH-wide initiative requires every NIH institute and center to come up with a plan for addressing disparities.

For Norman Anderson of Harvard, the NIH initiative is a hopeful sign. The next step is to convince policy-makers and others that Head Start, job-training programs and other interventions designed to increase socioeconomic status are really health interventions. Debates about minimum wage and other economic issues should factor health costs into their analyses, say other psychologists.

"If biomedical researchers found a pathophysiological process that was predictive of every single health outcome under the aegis of NIH, there would be an incredible, spare-no-expense effort launched to change that pathophysiological process," says Anderson. "With socioeconomic status, we have a social variable that's indeed predictive to all causes of death. Shouldn't we be interested in ways to change socioeconomic status in hopes of improving health outcomes?"

Rebecca A. Clay is a writer in Washington, D.C.