Well, the microwaves produced by any mobile phone will cause some damage. It's cooking your cells. Hold that thing next to your head for too long, and you may cause minor damage to your brain cells. Think of it as sticking your head into a microwave oven, only... less powerful 😛
But these types of waves are around us all the time, and no major health issues have been found so far. It's only a small portion of the spectrum that do cause any harm, and that's micro, x, and gamma rays. The rest, such as Wifi, are harmless. It's mobile phone and some forms of TV signals that can cause minor problems. So, in the long-run, there could be some problems. No one can say for sure right now.
Mine has been causing me a serious case of insomnia because I can't put it down when I get into bed. I have resorted to drugs and alcohol to induce a deep slumber/coma so I have to put it down.