The University of Warwick and Dartmouth College in America made a similar study on human happiness and mental health. They have surveyed over two million people and the results were shocking...
They found out that the biggest lows of our lives are experienced at the same age group. There was overwhelming evidence that happiness was U-shaped over life, bottoming out in middle age.
What's interesting is that it didn't really matter if the person they interviewed was a high-earning millionaire or someone working a regular 9-5 job.
It also didn't matter whether they were single or married, had children or not - the results were generally the same.
Prof Andrew Oswald, co-author of the report, said:
"You would expect people to get unhappier as they get closer to death but the opposite appears to be the case. People's levels of happiness and mental health are lowest in their mid-lives. It is a mystery why this happens but the evidence is incredibly strong.
The average, normal person experiences a kind of mid-life crisis in terms of happiness and mental health. I would like to think that just discovering this phenomenon will help people through their middle ages. It will be nice for them to know they are not alone."