Miserable middle age is a global phenomenon, according to an analysis of depression and happiness among 2m people in 80 countries. People everywhere follow a U-shaped curve of psychological well-being, with a nadir in their mid 40s.

Two economics professors, Andrew Oswald of Warwick University and David Blanchflower of Dartmouth College in the US, carried out the study, to be published shortly in the journal Social Science & Medicine.