Income and Health
The (positive) association between income and health has an economic explanation in Grossman's theory of health capital (Grossman, 1972). A wider multidisciplinary ' population health ' perspective is in R.G. While the idea that health and wealth are positively correlated has not been much contested (though there are issues around the direction of causation) the idea that relative income and, in particular, that unequal income distributions tend to lower population health has been much contested and the evidence for it is weak.
A more recent appraisal is Jones and Wildman (2008).