Epidemiologists and social scientists have noted for some time that relative inequality of a population predicts health outcomes. The higher up on the status ladder you are, the better your outcomes are. The lower, the worse. This effect persists even when we account for the quality of health care and other socio-economic variables. Researcher Michael Marmot calls this link the “social gradient in health”.
The common interpretation of the phenomenon is that it is related to stress and a sense of control:
Marmot calls the link between health and status “the social gradient in health.” One possibility is that it’s all related to a sense of control in one’s life. People lower down in the social order feel like they have less control, which can lead to stress that then negatively impacts health. (html)
Marmot sees stress, caused by disempowerment, as a central mechanism of the outcome:
The other way it affects health is through stress pathways. I talk about disempowerment: If you have little control of your life, you might smoke, drink, and so on, and you can’t do anything about the future anyway — so you might as well get drunk. There’s evidence that these stress pathways related to disempowerment impact negatively on cardiovascular diseases, diabetes, and mental illness. That starts from the beginning of life. (html)
A possible example: as economic inequality has deepened, the all-cause mortality trend has reversed in lower-class white populations. See Opioids, Alcohol, Suicide