Dr. Terence Cheng of the University of Melbourne's Institute of Applied Economic and Social Research said past evidence for "mid-life crises" was mixed because it came from cross sectional data. In other words, research on mid-life crises was based in comparing surveys of different people's happiness at different ages.
However, Cheng and colleagues tracked the happiness levels of thousands of people across three countries over multiple decades. They used nationally representative survey data from Australia, Britain and Germany.
"We have identified a clear 'U-shape' in human well being," Cheng said in a statement. "The jury's now in. People really do experience mid-life crises."
The study, "Longitudinal Evidence for a Midlife Nadir in Human Well-being," was completed in partnership with the University of Warwick and the London School of Economics.
"What is interesting is the consistency of the results in all of the three countries we examined," Cheng said. "Human happiness hits the lowest point around the ages of 40 to 42."
The U-shape is intriguing, Cheng said. It says happiness improves with age after middle life. This seems to contradict with general expectations because health is usually failing with age.
"We looked at the well-being of 'Mr. Jones' at age 35, 45, 55, and so on. This is important as the U-shape finding therefore does not arise from variations across different people, but rather within individuals," Cheng said. "Indeed all the more intriguing is that the U-shape pattern has been recently observed in research on great apes."
The findings were published as a working paper by the German-based Institute for the Study of Labor.