Marriage of Nature, Nurture Answers Race-Related Epidemiology Riddle

Community-based surveys have found that prevalence of psychiatric symptoms is higher among non-Hispanic whites than among blacks, even though blacks have greater rates of physical illness and earlier mortality, a disparity that has sometimes puzzled psychiatric epidemiologists.

Now University of Michigan researchers suggest a reason for this anomaly that ties together behavior and biology.

The apparently lesser rates of reported mental health symptoms occur despite generally lower socioeconomic status and greater social stress among blacks compared with whites. That seems puzzling, given the role that social factors play in both physical and mental health, wrote James Jackson, Ph.D., Katherine Knight, Ph.D., and Jane Rafferty, M.A., in the December 2009 American Journal of Public Health.

“African Americans have higher rates of 'psychological distress' although not of DSM diagnoses,” agreed Annelle Primm, M.D., M.P.H., director of APA's Office of Minority and National Affairs and deputy medical director of APA. “So people are suffering.”

How they deal with that suffering has short-term influences on psychiatric symptoms and long-term effects on physical ones, said the researchers.

“[W]e hypothesize that when individuals are chronically confronted with stressful conditions in daily life (e.g., poverty, crime, poor housing), they will engage in behaviors (e.g., smoking alcohol use and abuse, drug use, and overeating, especially comfort foods) that help alleviate the resulting symptoms of stress,” wrote Jackson, Knight, and Rafferty.

Coping Strategies Increase Mortality

However, those same coping strategies, combined with social, economic, and environmental inequalities contribute to chronic physical health ailments and early mortality later in life, they said.

The researchers support their hypothesis with data gathered from 1986 and 1989 in the Americans' Changing Lives study. The 2009 report covered 874 black respondents and 1,906 white respondents aged 25 and older.

“Among blacks, the relationship between stressors and meeting criteria for depression was stronger among those who had engaged in none of the unhealthy behaviors” than among those who did so, they found.

In contrast, the positive correlation between stressors and depression rose with higher levels of unhealthy behaviors among whites.

“Poor, black people buy better short-term mental health by selling out their long-term physical health,” Jackson said in an interview. Jackson is a professor of psychology and director of the Institute for Social Research at the University of Michigan.

Poor health behaviors alleviate stress but combine with the effects of poor living conditions to raise rates of lung disease, heart disease, hypertension, diabetes, cancer, and other chronic illnesses.

Age and gender differences influence these patterns too. Black men are protected in their early years both by being young and active and by engaging less in illegal drug use, smoking, and drinking, compared with whites, said Jackson. However, rates of those behaviors begin to rise in middle age as the men become less physically active.

Among some black women, overeating becomes a way of life early and continues through life, he said. High-calorie “comfort foods” and the social rituals surrounding their consumption have a positive protective effect in protecting against mental disorders, he said. “Consuming comfort foods may be a socially accepted, gender-appropriate way of dealing with chronic stress among this population.”

Biological Mechanism Proposed

Jackson's hypothesis doesn't rely on survey data alone to make the case. He posits a familiar biological mechanism to connect stress with coping behaviors and negative physical outcomes.

Stress initiates the cascade along the HPA axis that should end with cortisol shutting down stress-induced release of corticotrophin-releasing factor (CRF) and adrenocorticotropic hormone. In chronic stress, glucorticoid receptors are downregulated and CRF release continues, perpetuating a sense of anxiety.

Drawing on the work of Mary Dallman, Ph.D., a professor emerita of physiology at the University of California, San Diego, Jackson said that eating foods high in carbohydrates and fats serves to regulate release of CRF in chronic stress but also leads to greater abdominal fat storage.

This dietary approach to stress reduction also increases risk of developing type-2 diabetes, stroke, cardiovascular disease, and so on. Alcohol and smoking produce similar long-term effects.

Substance Use Has 'Protective Effects'

These drugs and foods are thus not consumed solely for momentary pleasure, said Jackson.

“The use of substances has a functional meaning,” he said. “They're not purely hedonic. They have material, protective effects.”

While African Americans were the focus of this study, Jackson emphasized that what he observes is a contextual effect that only masquerades as a racial effect.

“If you placed non-Hispanic whites in the same conditions, you would have the same effects through the same biological mechanism,” he said.

But, that's a big if, he added. It is difficult to fully adjust for the many ways that life experiences differ between white and black Americans.

“The intersection and interactions among race stratification with material, social, and psychological stratifications are extremely complicated,” he explained. The issues that differentiate blacks and whites can be structural (like income, employment status, housing), psychological (expectations), social (family structure, discrimination), and medical (chronic conditions), and they vary over the lifespan.

His team is using propensity-score analysis to look for a similar effect among whites who resemble blacks statistically and then compare behavior-by-stress interactions to observe if results are similar to those among blacks.

Resemblance to Whites Assessed

Eventually, they will stratify black respondents who have various factors in common with whites to see whether there is a lack of an effect, since the framework would also predict this outcome.

Jackson's work is part of an expanding literature in the last decade on the interaction of race, ethnicity, and socioeconomic status, said Donald Barr, M.D., Ph.D., an associate professor of sociology and an associate at the Center for Health Policy and the Center for Primary Care and Outcomes Research at Stanford University.

Disentangling the effects of race from socioeconomic status remains a problem, said Barr, a family medicine physician and author of Health Disparities in the United States: Social Class, Race, Ethnicity and Health (Johns Hopkins University Press, 2008).

Prior research has shown that these apparent differences between races are not caused by genetic patterns found in Africa, said Barr in an interview. But even after controlling for socioeconomic factors, race still has some effect on outcomes.

“The effect is due to racism or racial discrimination, especially through childhood and youth, as distinct from socioeconomic status,” said Barr. “It's race as a social construct, not a matter of common DNA.”

For instance, he noted, African Americans suffer from disproportionately higher rates of high blood pressure and stroke than white Americans, although some of the lowest hypertension rates in the world are found in sub-Saharan Africa. That difference suggests that social and cultural differences between black Americans and black Africans, not common ancestry, have led to elevated hypertension rates in the United States.

“This research needs replication and more study to figure out how to prevent disparities, promote wellness, and develop healthier coping styles,” said Primm. “But it also gives us clues about where to look for causes and effects.”

Jackson has already taken up that challenge.

“Like any hypothesis in science, it's testable,” he said. He and his colleagues are now working on a series of papers, using other data sets, in order to test his paradigm.

An abstract of “Race and Unhealthy Behaviors: Chronic Stress, the HPA Axis, and Physical and Mental Health Disparities Over the Life Course” is posted at <http://ajph.aphapublications.org/cgi/content/abstract/AJPH.2008.143446v1>.