Unfortunately, the only way to know for sure is to make side-by-side studies of people who use those technologies with those who use other, more "continuous" technologies (AMPS and CDMA), but no one has done this; compounding the problem is that AMPS has virtually disappeared worldwide AFAIK, CDMA is only used widely here in North America, and both GSM and CDMA are often found at the same shared cell sites.