The association between income inequality which creates psycho-social stress and longevity is of a curvilinear, concave nature. Low levels of income inequality are connected with shorter life expectancy. As inequality increases so does life expectancy until a point is reached where further increases in inequality lead to decreases in life expectancy. This finding is consistent with general theories of the effects of stress on performance as found in the fields of social psychology and sports medicine. In addition, we found that the life expectancy of populations is driven by factors such as perceived political control, the generosity of the welfare state, life-styles, GDP per capita and the poverty rate. Independently of which measure of income inequality was used or which statistical method was applied, these findings remained robust even when a number of alternative explanations were controlled for.