Lead researcher, professor Bengt Arnetz, claims, "The study strongly suggests that mobiles phone use is associated with specific changes in the areas of the brain responsible for activating and coordinating the stress system".
Another theory is that radiation may disrupt the production of the hormone melatonin, which regulates the body's internal rhythms. Close to half of the people in the study believed themselves to be "electrosensitive", reporting symptoms such as headaches and impaired cognitive function from cell phone use.
However, they proved to be unable to tell if they had been exposed to the radiation in the test. The group Powerwatch, which studies the effects of electromagnetic fields on health, suggests evidence is mounting that we should treat these devices in a more precautionary way. Director of Powerwatch director, Adasdair Philips, states, "This research suggests that if you need to make a phone call in the evening, it is much better to use a land line."