Washington, Jan 29 : Researchers from the University of Warwick and Dartmouth College have found a consistent international pattern in depression and happiness levels that leaves us most miserable in middle age.
In the study, the researchers used data on 2 million people, from 80 nations, and found that happiness levels followed a U shaped curve, with happiness higher towards the start and end of our lives and leaving us most miserable in middle age.
The scientists discovered that for both men and women the probability of depression peaks around 44 years of age.
The research team, economists Professor Andrew Oswald from the University of Warwick and Professor David Blanchflower from Dartmouth College in the US, believe that the U-shaped effect stems from something inside human beings.
They show that signs of mid-life depression are found in all kinds of people; it is not caused by having young children in the house, by divorce, or by changes in jobs or income.
"Some people suffer more than others but in our data the average effect is large. 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," Oswald said.
"What causes this apparently U-shaped curve, and its similar shape in different parts of the developed and even often developing world, is unknown. However, one possibility is that individuals learn to adapt to their strengths and weaknesses, and in mid-life quell their infeasible aspirations.
"Another possibility is that cheerful people live systematically longer. A third possibility is that a kind of comparison process is at work in which people have seen similar-aged peers die and value more their own remaining years. Perhaps people somehow learn to count their blessings," he added.
The study entitled "Is Well-being U-Shaped over the Life Cycle?" is to be published shortly in Social Science and Medicine.