Living in a society with massive income inequality—the US has greater income inequality than any other developed nation—makes people anxious, depressed, even physically sick.
The wealthiest and most unequal societies lag behind countries with fewer obvious advantages in every measure of health, happiness, and well-being. Rates of diabetes, hypertension, cancer, lung disease, and heart disease are higher than they are in more equal societies, such as Greece, Finland, Holland (where you can smoke), and Japan. Infant mortality rates are shocking.
Income inequality is the biggest cause of ill health in the world. The bad health effects of inequality are not confined to the poor, but spread like a pollutant throughout society. Having more poor people is not what makes more unequal societies sicker. Greater equality helps those at the bottom. Rich people and poor people alike are less healthy in more unequal countries.
Everyone receives roughly proportional benefits from greater equality. In more equal societies, everyone is better off. The vast majority of the population is harmed by greater inequality. Cooperation and friendship stimulate the reward centers in the brain, while the experience of social exclusion involves the same areas of the brain as physical pain. People who live in rich countries are under constant hormonal assault from the competitiveness and lack of connection in their lives.
One explanation for our poor health; the most powerful sources of stress affecting health seem to fall into three intensely social categories: low social status, lack of friends, and stress in early life. Add to that a culture based on competition for status, class-stratification, and criminalization of the lower class, and you have a sort of cycle of violence that ruins everyone's health. Violence is generally a response to threats to status: disrespect, humiliation, loss of face.
An experiment in India showed that boys of high and low caste performed at about equal levels on puzzles, with the low-caste boys performing a bit better. But when the boys were asked to state their fathers' names, where they were from, and their caste, the low-caste boys' performance plummeted. Likewise, in this country, African American youth lose confidence and their scores decline on tests, when told they are being evaluated against their white counterparts. It's a form of violence.
Despite historic heights of luxury in our modern societies, we talk as if our lives were a constant battle for psychological survival, struggling against stress and emotional exhaustion. Celebrities and the super-rich have a toxic effect on society, by inducing feelings of inferiority in the rest of the population. Their income should be redistributed in the name of public health.