Johann Hari is the New York Times bestselling author of Chasing the Scream, which is being adapted into a feature film. He was twice named Newspaper Journalist of the Year by Amnesty International UK. He has written for many of the world’s leading newspapers and magazines, including the New York Times, Le Monde, the Guardian, the Los Angeles Times, the New Republic, the Nation, Slate, El Mundo, and the Sydney Morning Herald. He was a lead op-ed columnist for the Independent, one of Britain’s leading newspapers, for nine years. He is a regular panelist on HBO's Real Time with Bill Maher. His TED talk, “Everything You Think You Know About Addiction Is Wrong,” has more than 20 million views.

Johann Hari: When I feel depressed, like loads of people I say, “I feel down,” right?

And as I was learning about the causes of depression and anxiety for my book 'Lost Connections' I started to realize—I don’t think that’s a metaphor. There’s this amazing professor at Stanford called Robert Sapolsky who, in his early twenties, went to live with a troop of baboons in Kenya. And it was his job to figure out: when are baboons most stressed out?

So his job was to hit them with little tranquilizer darts and then take a blood test and measure something called cortisol, which is a hormone that baboons and us release when we’re stressed. And baboons live in this hierarchy—so the females don’t, interestingly—but the men live in a very strict hierarchy. So if there’s 30 men, number one knows he’s above number two. Number two knows he’s above number three. Number 12 knows he’s above number 13. And that really determines a lot; it determines who you get to have sex with, it determines what you get to eat, it determines whether you get to sit in the shade or you’re pushed out into the heat. So really it's significant where you are in the hierarchy.

And what Professor Sapolsky found is that baboons are most stressed in two situations. One is when their status is insecure. So if you’re the top guy and someone’s circling which comes for you, you will be massively stressed.

And the other situation is when you feel you’re at the bottom of the hierarchy, you’ve been kind of humiliated. And what Professor Sapolsky noticed—and then it was later developed by other scientists—is, when you feel you’ve been pushed to the bottom, what you do is you show something called a submission gesture.

So you, baboons will raise— I say “you,” I assume no baboons are watching this, maybe they are—a baboon will put its body down physically or put it’s head down or put its bottom in the air and it will cover its head. So it’s clearly seems to be communicating: “Just leave me alone. You’ve beaten me, okay? You’ve beaten me.”

And what lots of scientists, like Professor Paul Gilbert in Britain and Professor Kate Pickett and Professor Richard Wilkinson, also in Britain, have really developed is this idea that actually what human depression is, in part—not entirely, but in part—is a form of a submission gesture. It’s a way of saying, “I can’t cope with this anymore,” right. Particularly people who feel they’ve been pushed to the bottom of hierarchies. Or who feel, if you remember the other stressful situations, when your status is insecure, it’s a way of just going, “Okay, I retreat. I don’t want this fight anymore. You’ve beaten me.” It’s a kind of very strong evolutionary impulse where you feel you’re under attack, to just submit in the hope that the stress and anxiety will then go away, that the sources of the stress and anxiety will then go away.

And one thing that’s so important, and that’s what Kate Pickett and Richard Wilkinson really developed, is they’ve shown that as inequality grows, depression and anxiety grow. They’ve shown this is a very robust effect, right. This helps us to explain it. If you live in Norway your status is relatively secure, right. No one’s that high, no one’s that low. Movement between where you are is not so extreme.

If you live in the United States, especially today, where we’re at the greatest levels of inequality since the 1920s, there’s a few people at the very top, there’s a kind of precarious middle, and there’s a huge and swelling bottom, right. So you can see why in the United States you’ve got more people who would be showing a submission gesture, who would be like, “Oh Jesus, I’ve been beaten,” than there would be in Norway.

This is why inequality is one of the drivers of depression and anxiety, and why dealing with inequality reduces inequality and anxiety. It’s one of the things that really shocked me actually. In the United States, the group with the lowest depression by far is the Amish. So I went and spent time with an Amish community.

The Amish live in these homogenous groups which are incredibly equal. The richest Amish is worth as much as the poorest Amish. They’re not showing submission gestures in the same way because they don’t fit—there’s a lot wrong with the Amish, don’t get me wrong. I’m not suggesting mass conversion to the Amish; I’m a gay man, believe me, I’m not—but we can learn from the fact that in these highly equal and homogenous groups you don’t have that extreme status stress. Now I don’t want to go as far as the Amish do, but moving closer to it would be one of the factors that would reduce depression and anxiety.