Money can buy happiness, research shows - but how much does it take?

The contentment comes from paying others to take on chores such as cleaning, cooking and gardening.

In this way, happiness can be bought in the form of free time, say scientists.

Psychology professor Elizabeth Dunn, from the University of British Columbia, Canada, co-led the study.

She said: "The benefits of buying time aren't just for wealthy people.

"We thought the effects might only hold up for people with quite a bit of disposable income, but to our surprise, we found the same effects across the income spectrum."

The scientists conducted a poll of 6,000 adults in the US, Canada, Denmark and the Netherlands.

Participants were questioned about the extent to which they spent money to buy themselves more free time each month.

They also rated their levels of happiness, or life satisfaction, and were quizzed about time stress.

It turns out, it doesn't take a lot of money to buy happiness, it just means spending the money you have on time-saving.

People who spent money on time-saving turned out to be more satisfied with their lives than those who did not, irrespective of income.

In another part of the study 60 adults were randomly given 40 US dollars (£30.70) to spend on either a time-saving or material purchase on different weekends.

They reported feeling happier when their spending secured them more free time.

Despite the benefits, few people choose to prioritise "buying time", the research showed.

Even in a sample of 850 millionaires, almost half spent none of their fortune on out-sourcing disliked tasks.

A survey of 98 working adults showed that only 2% would choose to spend a 40 dollar windfall on saving time.

Professor Dunn added: "Although buying time can serve as a buffer against the time pressures of daily life, few people are doing it even when they can afford it.

"Lots of research has shown that people benefit from buying their way into pleasant experiences, but our research suggests people should also consider buying their way out of unpleasant experiences."

The findings appear in the journal Proceedings of the National Academy of Sciences.