Susan J. Matt is a professor of history at Weber State University and the author of “Homesickness: An American History.”

ACCORDING to a recent Gallup World Poll, 1.1 billion people, or one-quarter of the earth’s adults, want to move temporarily to another country in the hope of finding more profitable work. An additional 630 million people would like to move abroad permanently.

The global desire to leave home arises from poverty and necessity, but it also grows out of a conviction that such mobility is possible. People who embrace this cosmopolitan outlook assume that individuals can and should be at home anywhere in the world, that they need not be tied to any particular place. This outlook was once a strange and threatening product of the Enlightenment but is now accepted as central to a globalized economy.

It leads to opportunity and profits, but it also has high psychological costs. In nearly a decade’s research into the emotions and experiences of immigrants and migrants, I’ve discovered that many people who leave home in search of better prospects end up feeling displaced and depressed. Few speak openly of the substantial pain of leaving home.

This emotional style became common among mobile Americans in the 20th century, but represented a departure from the past. In the 19th century, Americans of all stripes — pioneers, prospectors, soldiers and the millions of immigrants who streamed into the nation — admitted that mobility was emotionally taxing. Medical journals explored the condition, often referring to it by its clinical name: nostalgia....