A small-scale study suggests it could boost parts of the brain and the immune system.

Meditation has been practised since ancient times, mainly in the East.

There is increasing evidence that meditation is a useful and, for some people, a powerful therapy Dr Adrian White, University of Exeter

It is now catching on worldwide as a means to reduce stress or to help with pain caused by various illnesses.

Researchers at the University of Wisconsin-Madison in the United States enrolled 41 people in a trial of so-called "mindfulness" meditation.

It is a technique developed by an American stress reduction specialist - Jon Kabat-Zinn - for helping hospital patients deal with pain and discomfort.

Encouraging

Twenty five of the subjects attended a weekly class and one seven-hour retreat during the study; they were also given exercises to carry out at home. The others did not receive meditation training and acted as a control group.

After eight weeks, the researchers measured electrical activity in the frontal part of the brain. They say this region was more active on the left side in the individuals who meditated and was associated with lower anxiety and a more positive emotional state.

Participants were also given a flu jab at the start of the study and those who meditated had higher levels of antibody, say the researchers, led by Dr Richard Davidson.

"Although our study is preliminary and more research clearly is warranted we are very encouraged by these results," he said.

Caution

A British expert says the results - published in the journal Psychosomatic Medicine - are interesting but need further scrutiny.

"There is increasing evidence that meditation is a useful and, for some people, a powerful therapy," said Dr Adrian White of the department of Complementary Medicine at the University of Exeter.

"But we still need more information to determine who it helps and precisely what its benefits are."