There is no clear link between brain tumors and long-term cell phone use, according to a major new study from Denmark. Published in the British Medicine Journal (BMJ), the study looked at nearly 360,000 cellphone users over more than a decade, and is believed to be the largest study ever of its kind. Here's what you should know:
What exactly did the study find?
Over a 10-year period, people who used cell phones experienced similar cancer rates to people who didn't, says David W. Freeman at CBS News. They "were also no more likely to get a tumor in the part of the brain closest to where phones are usually held against the head."
Don't other studies say there is a link?
Yes. In May, for instance, the World Health Organization's International Agency for Research on Cancer concluded that cell phones are "possibly carcinogenic" and carry an "increased risk" of a certain type of brain cancer.
So what makes people so sure about this new study?
First of all, the study's massive size lends it credibility. But also, researchers matched data from a national cancer registry against cell phone contracts, avoiding "the need to contact individuals," and thus eliminating "problems related to selection and recall bias common in other studies," says Tara Parker-Pope of The New York Times.
Are there any problems with the study?
It has one glaring weakness: Researchers only tracked cell phone subscriptions, not actual cell phone use. Thus, a concrete link between cancer and unusually heavy cell phone use "cannot be ruled out," researchers concluded.
So there's still reason to worry?
That's debatable. Remember, there were also asterisks on the WHO study that classified cell phones as "possibly carcinogenic." That classification is "a long way from definitely cancer-causing," says Bryan Walsh at TIME. "Coffee and pickles, among other things" are also considered "possibly carcinogenic." Also given how ubiquitous cell phones are, "it's becoming nearly impossible for scientists to find a control group" that hasn't used them. "It's not surprising that the results of research into cell phones have been so confusing and contradictory."