Canadian psychoanalyst Elliott Jacques coined the term "midlife crisis" in 1965 to describe the period when adults are known to take stock of their lives and sink into depression. But a new study finds that this phenomenon is not unique to humans - and might be a result of evolution rather than modern life.
An international team of researchers studied 508 great apes in zoos and sanctuaries in the US, Japan, Canada, Australia and Singapore, and found chimpanzees and orang-utans can experience a midlife crisis, too. The apes' happiness was high in youth, fell in middle age and rose again in old age.
"We hoped to understand a famous scientific puzzle: why does human happiness follow a U shape through life?" says economist Professor Andrew Oswald from the University of Warwick, who was part of the research team.
"We ended up showing that it cannot be because of mortgages, marital break-up, mobile phones, or any of the other paraphernalia of modern life. Apes also have a pronounced midlife low."
The study, in the Proceedings of the National Academy of Sciences, is the first of its kind. The apes were assessed by keepers, volunteers, researchers and caretakers who knew them well. Their happiness was scored with a series of measures adapted from human subjective well-being measures.
The researchers point out that their findings do not rule out the possibility that economic events or social and cultural forces contribute part of the reason for the pattern in humans.