A 2006 study comparing depression rates in Nigeria to depression rates in North America found that across the board, women in rural areas were less likely to get depressed than their urban counterparts. And urban North American women—the most affluent demographic of the study—were the most likely to experience depression.

The mechanism seems simple: poor people are forced to share their time and resources more than wealthy people are, and as a result they live in closer communities. Inter-reliant poverty comes with its own stresses—and certainly isn’t the American ideal—but it’s much closer to our evolutionary heritage than affluence. A wealthy person who has never had to rely on help and resources from his community is leading a privileged life that falls way outside more than a million years of human experience. Financial independence can lead to isolation, and isolation can put people at a greatly increased risk of depression and suici.e. This might be a fair trade for a generally wealthier society—but a trade it is.

— Sebastian Junger, Tribe, Twelve, Ch. The Men and the Dogs, 2016