Scientists have discovered a surprising link between taking short naps and happiness.
And they have coined a new word to describe the contented state that follows a brief daytime doze - "nappiness".
Psychologist Professor Richard Wiseman, from the University of Hertfordshire, said previous research had shown naps under 30 minutes could make people more focused and creative.
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"These new findings suggest the tantalising possibility that you can also become happier by just taking a short nap," Professor Wiseman said.
"Similarly, longer napping is associated with several health risks and, again, this is in line with our results."
More than 1,000 people took part in the study, conducted for the Edinburgh International Science Festival which begins on Saturday.
Happiness scores were obtained from answers to psychological questions in an online survey which also asked for details of napping habits.
Among the participants, short nappers who dozed for less than 30 minutes at a time were more likely to be happy than either "long nappers" or "no nappers".
Two thirds of short nappers reported feeling happy compared with 56 per cent of long nappers and 60 cent of those who never napped.
"Many highly successful companies, such as ... Google, have installed dedicated nap spaces, and employees need to wake up to the upside of napping at work," Professor Wiseman said.
One study carried out by the American space agency NASA on sleepy military pilots found that taking a 26-minute nap while the co-pilot was in control boosted alertness by 54 per cent.
On the other hand, frequent hour-long naps are associated with an 82 per cent increase in the risk of heart disease.
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