A recent study by the IZA Institute for the Study of Labor found that people tend to experience their lowest happiness levels between the ages of 40 and 42.
Researchers analyzed survey data on life satisfaction at various ages from people 70 years and older. Nationally representative samples from the U.K., Australia, and Germany were included in the study. They found, on average, that people said they felt the least satisfied in their early forties; which researchers suspect is the time they're most likely to go through a mid-life crisis.
Of course, more research is needed to confirm these findings and determine why people's happiness levels plunge during these years.
Psychologist Katherine Muller, Psy.D., who was not part of the study, said it could be that people find it difficult to accept life at this age. Many major life events usually happen before the age of 40, so some people struggle with having these milestones behind them, says Muller.