A doctoral dissertation carried out at Lund University also found that groups of genes involved with behaviour and memory undergo changes due to repeated doses of radiation from mobile phones, the Sydsvenskan newspaper reports.
Doctoral candidate Henrietta Nittby and her adviser, Leif G Salford, are in agreement that studies involving mobile phones must continue.
Nearly a decade ago, Salford was involved in a separate study which revealed that the electromagnetic radiation from mobile telephones created openings in the blood-brain barrier.
The openings allowed the blood-borne protein to leak into the brain, which caused a small percentage of brain cells to die.
In Nittby's study, rats were exposed to electromagnetic radiation twice a week for 55 weeks. While the rats' behaviour remained unchanged, their short term memory worsened when compared to a control group which had not been subjected to the radiation.
In addition Nittby discovered that, while individual genes didn't change, groups of genes in brain cells involved with behaviour and memory did display a number of small changes.
Currently, no one knows for certain whether radiation from mobile phones is harmful to human beings.
Several countries have nevertheless issued warnings cautioning children from talking too much on mobile phones and to use hands free devices.