Hold your cellphone against your head too long and you can get a brain tumor. Text too often and you can forget how to spell. Converse on your Bluetooth while waiting in line and annoy everyone around you.

One of those statements is undeniably true, one could be true, and one—about brain tumors—is probably false, according to a new study in Environmental Health Perspectives.

Because data is sparse about cellphone use by youngsters and about use periods longer than 15 years, be prepared for ongoing speculation about how cellphones affect your brain. And be mindful, the study says, that "Research cannot in principle prove the complete absence of an effect, but only place limits on its possible magnitude.”