A Swedish study has shown that radiation emitted by the world's most common mobile phones damages the brains of rats.

According to Environmental Health Perspectives, Swedish neurosurgeon Leif Salford and his team tested the radiation emitted from global system for mobile communications (GSM) phones on rats between the ages of 12 weeks and 26 weeks.

Three groups of rats were exposed for two hours to GSM mobile phone electromagnetic fields (EMF) of different strengths.

The study found that EMF exposure was associated with neuronal damage in the rats' brains, and that increased exposure caused increased damage.

The researchers claimed that the age group of the rodents tested is equivalent to that of human teenagers. GSM phones are the most commonly used around the world, particularly in Europe, Asia and the Middle East.

The study's authors said the situation of the growing brain might deserve special concern, since biological and maturational processes are particularly vulnerable.

"We cannot exclude that after some decades of often daily use, a whole generation of users may suffer negative effects as early as middle age," the report said.

Both the World Health Organisation and the US Food and Drug Administration have argued that there is no evidence that mobile phone radiation is harmful to users. But both have also acknowledged that no absolute evidence exists to the contrary.