Parker-Pope, Tara. “The Midlife Crisis Goes Global.” New York Times, January 30, 2008.

The midlife crisis, a time of self-doubt and turmoil familiar to many in their 40s and 50s, is often viewed as a phenomenon of Western culture. But new research suggests that people all over the world are miserable in middle age.

Those are the surprising findings from a worldwide study of two million people from 80 countries. The researchers, economists Andrew Oswald from the University of Warwick in England and David Blanchflower from Dartmouth College in the United States, found that happiness levels followed a U-shaped curve, with happiness higher towards the start and end of our lives. Across cultures, they found, depression and unhappiness typically strike people in midlife.

The findings are important because other studies have suggested that psychological well-being stays relatively flat and consistent as people age, the researchers said. The latest report, to be published in Social Science & Medicine, analyzed information from several sources. Data was collected from 500,000 randomly sampled Americans and West Europeans from large surveys. The authors also analyzed data on the mental health levels of 16,000 Europeans, the depression and anxiety levels among a large sample of British citizens, and data from “The World Values Survey,” which provides samples of people in 80 countries.

The researchers found that for both British men and women, the probability of depression peaks around 44 years of age. In the United States, unhappiness peaks at around age 40 for women and 50 for men. They found the same U-shape in happiness levels and life satisfaction by age for people living in 72 countries.

The authors noted that signs of midlife depression are found in all kinds of people and not just those affected by divorce or changes in jobs or income.

“Some people suffer more than others, but in our data the average effect is large,” said Dr. Oswald, in a University of Warwick news release. “It happens to men and women, to single and married people, to rich and poor, and to those with and without children. Nobody knows why we see this consistency.”

Despair in midlife comes on slowly, but the good news is that it doesn’t last.

“It looks from the data like something happens deep inside humans,” Dr. Oswald said. “Only in their 50s do most people emerge from the low period. But encouragingly, by the time you are 70, if you are still physically fit, then on average you are as happy and mentally healthy as a 20-year-old. Perhaps realizing that such feelings are completely normal in midlife might even help individuals survive this phase better.”