Relax, take a nap. It'll do you good and make you work harder, say Spanish experts.

The siesta increases workers' productivity, dispels anxiety and prevents mental overload, according to a study published on Friday by the College of Psychologists in Andalusia – admittedly the sleepiest region in Spain.

An afternoon snooze enables your brain to rest and relaxes your body and muscles, which in turn lifts stress and improves powers of perception, says Cesar Escalante, who headed the research. "By promoting the memory and concentration, the siesta helps you to begin a new stage of cerebral activity in a fresher, more comfortable way," he says.

However, you mustn't overdo it. The siesta should be only 10 to 40 minutes. Any longer, and you may have difficulty waking up, feel even wearier and be in a bad mood. "Too much rest in the afternoon can disturb normal sleep patterns," Dr Escalante says.

But his research confirms the idea that, with more rest, people are more productive. Our level of perceptiveness falls off at around 9pm, he reckons, remains dormant until dawn, recovers through the morning and declines again between 2pm and 5pm "which is the ideal time to take a siesta".

The siesta has been deeply rooted in Spain for centuries. Legend says it was perfected by the 16th-century emperor, Charles V, who retreated to his throne after lunch, grasping one of the heavy keys of his palace until it clattered to the stone floor and woke him up.

When the Socialists won power and readied Spain for EU membership in 1986, they tried to drag habits into line with the rest of Europe. The attempt was soon dropped, and it remains difficult to rouse anyone official between 2pm and 5pm, or even, in these dog days, any time in the afternoon.

Dr Escalante's report was released, significantly, before lunch. Now, if you'll excuse me, I'll just go and put my head down...