Martin Roosli of the Swiss Tropical and Public Health Institute in Basel surveyed 1000 young people (age 7-19) in Norway, Denmark, Sweden and Switzerland. Sadly, 352 of the subjects had a brain tumor and 646 were healthy controls from the same demographics as the test group.
The research team analyzed the survey data and couldn’t find any link between mobile phone usage and brain tumors. They also could not find any increase in tumors that were located in areas of the head receiving the largest amount of exposure.
They did not account for the fact that teens and tweens mostly text and don't call much. Oh well. Use cells with caution or don't. There's a study to support you either way.