MONDAY, Nov. 19 (HealthDay News) -- Chimpanzees and orangutans can suffer a midlife crisis just like people do, according to a new study.

The finding suggests that evolution may play a role in what has been thought of as a human pattern of behavior.

Researchers studied 508 chimpanzees and orangutans living in zoos and sanctuaries in Australia, Canada, Japan, Singapore and the United States. Their happiness was assessed by keepers, volunteers, researchers and caretakers who knew the great apes well.

The results showed that the happiness of chimpanzees and orangutans follows a U-shape during their lives. It's high in their youth, falls in middle age and rises again in old age.

The same general pattern of happiness occurs in people, which suggests that it may have evolved in the common ancestors of humans and great apes.

"We hoped to understand a famous scientific puzzle: Why does human happiness follow an approximate U-shape through life? We ended up showing that it cannot be because of mortgages, marital breakup, mobile phones or any of the other paraphernalia of modern life. Apes also have a pronounced midlife low, and they have none of those [things]," Andrew Oswald, an economist at the University of Warwick, in England, said in a university news release.

Another study author, Alex Weiss, a psychologist at the University of Edinburgh, in Scotland, added: "Based on all of the other behavioral and developmental similarities between humans, chimpanzees and orangutans, we predicted that there would be similarities when looking at happiness over the lifespan, too. However, one never knows how these things will turn out, so it's wonderful when they are consistent with findings from so many other areas."

The study was published in the current issue of the Proceedings of the National Academy of Sciences.

More information

GoodTherapy.org has more about midlife transitions.