This week's Economist reports that low social standing leads to a lowering of autoimmune response systems in primates ("Social Status and Health: Misery Index" April 14, 2011).
Many years ago I helped Jack Fiedler write a book analyzing the economic relationship between mental health and physical health. Using federal data on patient expenditures in Michigan and Georgia we discovered that, holding all else constant, patients who received mental health treatments reduced their physical health expenditures (The Medical Offset Effect and Public Health Policy, Praeger 1989). Treating people's mental distresses saved money for the overall health care system when reasonable coverage limits were set. Ignoring mental illness costs society heavily.
No doubt, physical illness can also create mental illness. But in the experiments reported by The Economist, the researchers controlled for physical health and then exposed the macaques to a situation in which their social standing was lowered. That change induced a physiological deterioration of their immune systems. The experiments, if they could be applied to humans, would give a measure of support to those who argue that greater social equality is an important factor in social welfare, as measured by physical well-being. It's not at all clear how public policy can affect social standing, except, as Robert Frank has argued, to reduce conspicuous consumption across the board.
At the same time, a loss of personal autonomy and freedom experienced by intrusive policies could also negatively affect one's physical characteristics, including autoimmune
functions. Much more work will need to be done before this research can guide public policy.
[Update: A commenter noted that the article had not specifically mentioned the autoimmune system. I corrected the text. Thanks!]