There's a reason that most so-called primitive cultures have avoided the depression epidemic afflicting industrialized nations. In a provocative book, a clinical psychologist suggests that adopting more "hunter-gatherer" habits can help us escape the blues. According to the latest research, about one in four Americans — more than 70 million people — will meet the criteria for major depression at some point in their lives. The rate of depression in industrialized societies has been on the rise for decades — it’s roughly 10 times higher today than it was just two generations ago. How can people possibly be so much more vulnerable to depression now? And how do you make sense of the fact that even though antidepressant use has skyrocketed in recent years, the rate of depression in the United States hasn’t declined, but rather increased?