Studies have found no increased risk of cancer associated with cell phone use according to both the American Cancer Society and National Cancer Institute. However, the use of radiofrequencies so close to the head may still have other effects. These yet unknown effects appear to include energy use by brain cells if the findings of a February 2011 study in JAMA are any indication. This energy use isn't greater than other natural activities, but researchers stress the use of hands-free devices just to be safe. Read more about the study finding that brain regions near cell phone antennas use more energy.