Why do some societies have much higher rates of mental illness than others? And why have some seen anxiety and depression levels skyrocket in the last four decades? Why are Americans three times as likely as the Dutch to develop gambling problems? Why is child welfare much lower in New Zealand than in Japan? As this groundbreaking study shows, the answer to all these questions lies in inequality. Wilkinson and Pickett describe how it affects us individually, how it alters thinking, emotions, and behavior. They present overwhelming evidence that material inequalities have profound psychological consequences: when the gap between rich and poor widens, the tendency to define and value ourselves and others on the basis of superiority and inferiority grows. And they question the concept that human beings are by nature selfish and competitive, and also the idea that inequality is the result of "natural" differences in individual ability. This book shows that societies based on equality, reciprocity and the will to share generate much higher levels of well-being, while showing us the path that leads to them.