When people are under chronic stress, they tend to smoke, drink, use drugs and overeat to help cope with stress. These behaviors trigger a biological cascade that helps prevent depression, but they also contribute to a host of physical problems that eventually contribute to early death. That is the claim of University of Michigan social scientist James S. Jackson and colleagues in an article published in the May 2010 issue of the American Journal of Public Health. The theory helps explain a long-time epidemiological puzzle: why African Americans have worse physical health than whites but better psychiatric health. "People engage in bad habits for functional reasons, not because of weak character or ignorance," says Jackson, director of the U-M Institute for Social Research. "Over the life course, coping strategies that are effective in 'preserving' the mental health of blacks may work in concert with social, economic and environmental inequalities to produce physical health disparities in middle age and later life." In an analysis of survey data, obtained from the same people at two points in time, Jackson and colleagues find evidence for their theory. The relationship between stressful life events and depression varies by the level of unhealthy behaviors. But the direction of that relationship is strikingly different for blacks and whites. Controlling for the extent of stressful life events a person has experienced, unhealthy behaviors seem to protect against depression in African Americans but lead to higher levels of depression in whites. "Many black Americans live in chronically precarious and difficult environments," says Jackson. "These environments produce stressful living conditions, and often the most easily accessible options for addressing stress are various unhealthy behaviors. These behaviors may alleviate stress through the same mechanisms that are believed to contribute to some mental disorders -- the hypothalamic-pituitary-adrenal cortical axis and related biological systems." Since negative health behaviors such as smoking, drinking alcohol, drug use and overeating (especially comfort foods) also have direct and debilitating effects on physical health, these behaviors -- along with the difficult living conditions that give rise to them -- contribute to the disparities in mortality and physical health problems between black and white populations. These disparities in physical health and mortality are greatest at middle age and beyond, Jackson says. Why? "At younger ages, blacks are able to employ a variety of strategies that, when combined with the more robust physical health of youth, effectively mask the cascade to the negative health effects," Jackson said. "But as people get older, they tend to reduce stress more often by engaging in bad habits." Black women show heightened rates of obesity over the life course, he points out. In fact, by the time they are in their 40s, 60 percent of African American women are obese. "How can it be that 60 percent of the population has a character flaw?" Jackson asks. "Overeating is an effective, early, well-learned response to chronic environmental stressors that only strengthens over the life course. In contrast, for a variety of social and cultural reasons, black American men's coping choices are different. "Early in life, they tend to be physically active and athletic, which produces the stress-lowering hormone dopamine. But in middle age, physical deterioration reduces the viability and effectiveness of this way of coping with stress, and black men turn in increasing numbers to unhealthy coping behaviors, showing increased rates of smoking, drinking and illicit drug use." Racial disparities in physical illnesses and mortality are not really a result of race at all, Jackson says. Instead, they are a result of how people live their lives, the composition of their lives. These disparities are not just a function of socioeconomic status, but of a wide range of conditions including the accretion of micro insults that people are exposed to over the years. "You can't really study physical health without looking at people's mental health and really their whole lives," he said. "The most effective way to address an important source of physical health disparities is to reduce environmentally produced stressors -- both those related to race and those that are not. We need to improve living conditions, create good job opportunities, eliminate poverty and improve the quality of inner-city urban life. "Paradoxically, the lack of attention to these conditions contributes to the use of unhealthy coping behaviors by people living in poor conditions. Although these unhealthy coping behaviors contribute to lower rates of mental disorder, over the life course they play a significant role in leading to higher rates of physical health problems and earlier mortality than is found in the general population." The work was supported by the National Institute of Mental Health.