Unnatural Causes, a PBS documentary, asks the pointed question "Is Inequality Making Us Sick" and answers strongly affirmative. According to information presented in the video series, poverty is correlated with disease, more so than any other socioeconomic variable. This correlation is more than the obvious fact that (in the US at least) you have to have money to see a doctor. The series argues convincingly that there may be a causative factor in poverty that predisposes people to illness, weakened immune systems, increased heart disease, and cancer: increased stress. While our society often thinks of 9-5 businessmen as stressed out, the cortisol levels of the on-call janitors, cooks, and welfare recipients tests out as significantly higher.
Cortisol has been shown by numerous scientific studies to lead to disease. However, the ability to manage and control our circumstances may be the actual barometer of cortisol levels in humans. If that is true, then it will take more than just increased wealth and decreased stress to bring healthier outcomes to the majority of Americans. They will have to have a feeling of control over their lives, too. Furthermore, correlation does not prove causation: poverty need not necessarily be stressful, so poverty need not necessarily lead to poor health. However, the sociologists interviewed in the series may not be concerned with such nit-picking as long as the overwhelming correlation holds.