Mobile phones damage key brain cells and could trigger the early onset of Alzheimer's disease, a study suggests.
Researchers in Sweden have found that radiation from cell phone handsets damages areas of the brain associated with learning, memory and movement.
The study, which was carried out on rats, is the latest twist in the long-running debate over whether cell phones are a health risk.
Scientists have yet to find any conclusive evidence that cell phones damage the human brain. This latest study was carried out by Professor Leif Salford and colleagues at Lund University in Malmo.
Lab tests
They experimented on rats aged between 12 and 26 weeks. Their brains are regarded as being in the same stage of development as teenagers. The rats were exposed to two hours of radiation, equivalent to that emitted by cell phones.
Their brains were examined under a microscope 50 days later. The researchers found that rats which had been exposed to medium and high levels of radiation had an abundance of dead brain cells.
Professor Salford said there was good reason to believe that cell phones could have the same effect on humans. "A rat's brain is very much the same as a human's. They have the same blood-brain barrier and neurons," he told BBC News Online. "We have good reason to believe that what happens in rat's brains also happens in humans."
Prof Leif Salford, Lund University
Professor Salford said that there was also a chance exposure to cell phone radiation could trigger Alzheimer's disease in some people. "What we are saying is those neurons that are already prone to Alzheimer's disease may be stimulated earlier in life. 
"However, this theory is hypothetical. We do not have evidence yet that the human brain is affected in this way."
The study is published in Environmental Health Perspectives - the journal of the US government's National Health Institute of Environmental Health Sciences. Writing in the journal, the researchers concluded: "We cannot exclude that after some decades of often daily use, a whole generation of users may suffer negative effects maybe already in their middle age."