By Paul Rincon BBC News Online science staff, at the BA festival

Childhood cancer patients suffer less pain when placed under hypnosis, scientists have claimed.

Children who had been hypnotised in trials reported they had less pain from medical procedures as well as cancer-related pain.

Dr Christina Liossi, from University of Wales, Swansea, suggested there was even tentative evidence that hypnosis prolonged the lives of cancer patients.

The research is being presented at the BA Festival of Science in Exeter.

In one study, 80 children were placed in four groups: two experimental groups who were treated with an anaesthetic and hypnosis.

Two control groups were just given the anaesthetic.

"All [40] children who used hypnosis with a local anaesthetic felt much less pain than children who were just given the local anaesthetic," said Dr Liossi.

The children, aged six to 16, were placed under hypnosis by experts and then taught to hypnotise themselves before they underwent procedures.

Children not treated with hypnosis were talked to and counselled instead.

"We asked children to rate their pain from 0 to 5 on a graded scale. Before we perform hypnosis we ask them to rate their pain on this scale," Dr Liossi explained.

"Then we introduce hypnosis and then we ask them to rate pain again and they report much less."

Brain changes

Other evidence presented at the festival also supports the idea that hypnosis is a genuine physical state and that people are not simply deceiving themselves into thinking they are hypnotised.

Individuals who are highly susceptible to being placed under hypnosis show that there are changes in the left frontal cortex of the brain and a structure called the cingulated gyrus when viewed through a functional MRI (magnetic resonance imaging) scanner.

"The frontal lobe is concerned with our planning, our future actions, our analysis of the here and now, our critical evaluation and the things we do so we don't make silly mistakes," said Dr John Gruzelier of Imperial College, London.

"If you think about what the hypnotist does, he asks you to go with the flow and not critically analyse what you're doing."

Dr Liossi suggested there was even evidence that hypnosis might prolong life in adult cancer patients.

"There are some studies and there are some encouraging results from these," she said.

Adult cancer patients placed under hypnosis show fewer cancer-related symptoms such as nausea, vomiting and pain, said Dr Liossi.

"There are some studies and there are some encouraging results from these that hypnosis can probably improve the survival of cancer patients.