The largest-ever study of cell phones, known as the Interphone study, released its long-term results in May of 2010 and found no increased risk for benign or cancerous brain tumors, except at its highest level of use, a level deemed "implausible" as a comparison to real-life by the investigators. Even this link was only seen with benign tumors, not with cancer.
So why does the fear of cell phones' frying our brains still persist? The inconsistency in the data fuels the concern, Volkow says.
"Some studies have shown a significant association with cancer, others show the opposite," she said. "When you have data that is not consistent there is uncertain and uncertainty of course generates fear."
Especially considering the integral, frequent, increasing role that cell phones play in both our work and home lives. The number of mobile phone users has gone from 7.6 million in 1991 to 223 million in those older than 13 as of 2010, according to Nielsen industry statistics.
What's more, more than half of Americans age 25 to 29 use only cell phones as a means of communication and do not live in a household that even has a landline.
It also doesn't quell fears when doctors publicly advocate for cell phone precautions. In 2008, CNN Chief Medical Correspondent Sanjay Gupta, along with Cedars-Sinai Medical Center brain surgeon Dr. Keith Black said that they use earpieces instead of holding the phone against their heads out of fear of brain tumors.
Also in 2008, the director of Cancer Research at the University of Pittsburgh bolstered concerns about cell phone dangers when he released a controversial memo to his staff concerning modified cell phone practices to ward off potential harm:
"Although the evidence is still controversial, I am convinced that there are sufficient data to warrant issuing an advisory to share some precautionary advice on cell phone use," Dr. Ronald Herberman wrote in his memo.
He went on to warn that children shouldn't use cell phones except in emergency situations because "the developing organs of a fetus or child are the most likely to be sensitive to any possible effects of exposure to electromagnetic fields."
And many other doctors take this better safe than sorry approach. Dr. Andrew Sloan, director of the Brain Tumor and Neuro-Oncology Center at University Hospitals Case Medical Center in Cleveland, agrees that there's no "definitive proof" that cell phones are bad. But he still advises patients to use speaker phones or ear buds when talking for prolonged periods of time because, "why take the chance?"
With doctors advising patients to "play it safe," it's hard to shake the feeling that cell phones may be unsafe.
That researchers were able to show a consistent effect on the brain through prolonged cell-phone use is "landmark," said Dr. Maciej Lesniak, director of neurosurgical oncology and neuro-oncology research at the University of Chicago.
"Previous articles have tried to link cell phones to brain tumors based on large population studies, but those studies have many inherent flaws and too many variables to control," he said.
This experimental kind of research lays the groundwork for further research into exactly what's going on in the brain, whether harmful or not, when people use cell phones over long periods of time, he adds.
That said, there is little more than can be gleaned from this study beyond the fact that cell phones are doing something to the brain and increasing activity.
"Clearly there is an acute effect, and the important question is whether this acute effect is associated with events that may be damaging to the brain or predispose to the development of future problems such as cancer as suggested by recent epidemiological studies," Smullen said.
"Cell phones have become an essential part of our culture both for personal reasons and for work ... they are here to stay, but we need to evaluate whether cell phone design and usage needs to be adjusted to avoid or minimize potential risks," she adds.