Research from Harvard finds that living in states with higher income inequality makes people, especially women, more susceptible to major depression. The study drew on data regarding 34,653 respondents to the National Epidemiological Survey on Alcohol and Related Conditions.
Pabayo, R., Kawachi, I., Gilman, S; Income inequality among American states and the incidence of major depression. Journal of Epidemiology & Community Health. Online September 24, 2013. doi:10.1136/jech-2013-203093
Of further interest:
Income inequality is linked to depression, study finds (LA Times)