They are even more dissatisfied than teenagers and the elderly, a study for the government found.
More than 3,600 people were asked to score their wellbeing on a scale of one to 10 as part of a survey for Defra.
Men, who rated their youthful happiness as 7.3, plunged into an early mid-life crisis with those aged 35-44 reporting satisfaction levels at 6.8.
The overall average satisfaction level for men and women was 7.3 in England, suggesting that individuals are generally fairly content.
Seventy-four per cent of people said they felt generally positive about themselves.