TUESDAY, Feb. 22 (HealthDay News) -- A one-hour cell phone conversation stimulates the areas of your brain closest to the phone's antenna, but experts say they still have no idea whether these effects pose any long-term health risk.

"We don't know whether this is detrimental or whether it could have some potential beneficial effects. We don't know one way or the other," said Dr. Nora Volkow, who is lead author of the study published in the Feb. 23 issue of the Journal of the American Medical Association. "Studies need to be done to see if there are long-lasting consequences. It's an important question."

For the time being, the best bet is to use an ear piece or the speaker phone, "particularly in children and adolescents whose brains are much more vulnerable to insults of certain kinds," said Volkow, who is director of the U.S. National Institute on Drug Abuse.

Or you could follow the example of kids and teenagers and use text messaging, so the phone is nowhere near your head.

"These solutions are so simple, trivial," Volkow noted.

There's been a lengthy scientific back-and-forth on whether cell phone use -- now practically ubiquitous across the world -- is harmful to your health, and specifically whether it can cause brain cancer, but no definitive answer has yet emerged.

For this study, 47 volunteers were brought into a lab at the U.S. National Institutes of Health, where they had cell phones positioned at both their left and right ears.

Researchers measured metabolism of glucose in the brain -- a measure of how hard the organ is working -- using positron emission tomography (PET) scans. Metabolism in the orbitofrontal cortex and temporal pole regions of the brain, those closest to the antenna, was about 7 percent higher when the right phone was in the "on" position than when both phones were off.

The brain activity decreased with distance from the antenna.

"That [level of brain activity] is what we see normally when viewing a movie," said Volkow.

But the simulation was exactly that, a simulation, and not the typical scenario where people walk, drive and eat while not only listening to their cell phone but also talking on the gadget, experts noted.

"It is not real world," said Dr. Giuseppe Esposito, chief of nuclear medicine at Georgetown University Hospital and an associate professor of radiology at Georgetown University Medical Center in Washington, D.C. "Obviously, this is not what you do normally," he added.

"I don't think we can draw any conclusions as to the health effects of cell phones in general or radiofrequency simulations from this study," he noted.

No one yet knows whether "exposure to these external sources, two to three hours a day for five to 10 years [is going to result] in any untoward effects," Volkow said. "And if you get exposed very early on when the brain is very plastic, would there be any detrimental effects? That's an important question that needs to be addressed."

Nor is it clear what part of the brain might be affected, given that older cell phones had antennas closer to the brain than newer ones, like those used in this study, which are closer to the mouth.

Volkow is now planning a retrospective study to see if long-time cell phone users -- say, two hours a day over 10 years -- have any obvious health consequences.

In a statement, John Walls, vice president of public affairs for CTIA-The Wireless Association, had this to say: "Since we are not a scientific organization, with respect to the matter of health effects associated with wireless base stations and the use of wireless devices, CTIA and the wireless industry have always been guided by science, and the views of impartial health organizations. The peer-reviewed scientific evidence has overwhelmingly indicated that wireless devices, within the limits established by the [U.S. Federal Communications Commission], do not pose a public health risk or cause any adverse health effects."

More information

For more on cancer and cell phones, visit the U.S. National Cancer Institute.

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