Middle-aged are grumpiest, says expert. Hmmfff.

London: The middle-aged happen to be the grumpiest of the lot because happiness follows a U-shaped curve during one's lifetime, experts say.

Overall satisfaction begins to drop as early as late twenties and does not begin to recover until well past 50 years, says Bert van Landeghem of the Maastricht University in Belgium.

While young adults are carefree and full of hope and the over 50s have come to terms with the trials of life, the research indicates that those in the middle feel weighed down by the demands on them, the Telegraph reports.

According to van Landeghem, happiness did return with age, but warned that older people did not actually recapture the spirit of their youth. They simply learnt to be satisfied with their lot.

"A U-shaped happiness curve does not necessarily imply that a 65-year-old prefers his own life to the life of a 25-year-old," he said.

"Both the 25-year-old and 65-year-old might agree that it is nicer to be 25 than to be 65. But the 65-year-old might nevertheless be more satisfied, as he has learned to be satisfied with what he has," he added.

Last month, Lewis Wolpert, emeritus professor of biology at the University College London and the author of "You're Looking Very Well," said happiness could peak as late as 80.

Wolpert added: "From the mid 40s, people tend to become ever more cheerful and optimistic, perhaps reaching a maximum in their late 70s or 80s."

According to a study by the American National Academy of Sciences based on a survey of 341,000 people, enjoyment of life begins an upward trend in the late 40s and does not peak until 85.

Bert van Landeghem will present his research at the Royal Economic Society annual conference at Royal Holloway at the University of London this week.