The term is said to have been coined by Oliver James (born 1953) is a clinical psychologist.
According to Wikipedia (here: http://en.wikipedia.org/wiki/Affluenza) it is an “illness” with the following symptoms:
1. The bloated, sluggish and unfulfilled feeling that results from efforts to keep up with the Joneses
2. An epidemic of stress, overwork, waste and indebtedness caused by the pursuit of the American Dream
3. An unsustainable addiciton to to economic growth.