Teenagers who talk on the phone a lot, and hold their cell phones up to their right ears, score worse on one type of memory test. That’s the finding of a new study. That memory impairment might be one side-effect of the radiation that phones use to keep us connected while we’re on the go.

Nearly 700 Swiss teens took part in a test of figural memory. This type helps us recall abstract symbols and shapes, explains Milena Foerster. She’s an epidemiologist. That’s someone who studies disease patterns within a population. She worked on the study as part of a team while Foerster was at the Swiss Tropical and Public Health Institute in Basel, Switzerland. (She is now at the World Health Organization’s International Agency for Research on Cancer in Lyon, France.)

Educators and Parents, Sign Up for The Cheat Sheet Weekly updates to help you use Science News for Students in the learning environment Client key* E-mail* Go

Teens participated in memory tests twice, one year apart. Each time, they had one minute to memorize 13 pairs of abstract shapes. Then they were shown one item from each pair and asked to match it with one of five choices.

The study volunteers also took a test of verbal memory. That’s the ability to remember words. The two memory tests are parts of an intelligence test.

The researchers also surveyed the teens on how they use mobile phones. And they got call records from phone companies. The researchers used those records to estimate how long the teens were using their phones. This allowed the researchers to calculate how big a radiation exposure each person could have gotten while talking.

All cell phones give off energy in the form of radiofrequency electromagnetic fields, or RF-EMFs. Radio and TV broadcasts also use this type of energy. So do microwave ovens and some other gadgets.

For a phone, that energy carries information, in the form of calls or texts between phones and cell phone towers. That radiation also can travel into people’s bodies as they use their phones. And some of its energy can be absorbed by the body. So far, scientists have not shown that radiation from phones causes harm, says the Federal Communications Commission. Research is ongoing, this U.S. agency notes.

Mobile phones send and receive data from cell phone towers in the form of electromagnetic energy. They use a type of energy called a radiofrequency electromagnetic field, or RF-EMF. pedrosala/iStockphoto

A phone user’s exposure to RF-EMFs can vary widely. Some teens talk on their phone more than others. People also hold their phones differently. If the phone is close to the ear, more radiation may enter the body, Foerster notes.

Even the type of network signal that a phone uses can matter. Much of Switzerland was using an older “second-generation” type of cell-phone network when the group collected its data. That type of network can expose people to between 100 and 500 times as much RF-EMF radiation as newer networks, the study reports. Many phone carriers have moved away from such networks. And more companies plan to update their networks within the next few years.

The teens’ scores in the figural memory tests were roughly the same from one year to the next. But those who normally held their phone near their right ear, and who were also exposed to higher levels of radiation, scored a little bit worse after a year. No group of teens showed notable changes on the verbal memory test.

Why might one type of memory be linked to cell phone use, but not another? Foerster and her colleagues think it could have to do where different memory centers sit in the brain. The site that deals with the ability to remember shapes is near the right ear. “This may suggest that indeed RF-EMF absorbed by the brain is responsible” for the results, said coauthor Martin Röösli. He, too, is an epidemiologist in Basel at the Swiss Tropical and Public Health Institute.

The report was published last July in Environmental Health Perspectives.

Should you worry?

There’s no need to swear off your cell phone yet. For one thing, the link was not very strong between the estimated radiation dose and drop in their memory scores for some teens.

It’s also hard to gauge both radiation exposure and phone use precisely. Teens thought that they spent much more time talking on the phone than they actually did, according to call records. But the researchers only had call records for some of the study’s teens. So they had to estimate how much time the others had spent on their phones. And records from phone companies likely wouldn’t include calls on phone apps such as WhatsApp or Skype.

What’s more, a correlation between two things does not prove one caused the other. “I would not draw any causal conclusions from our study,” says Foerster. The findings, her team says, should be viewed only as “preliminary evidence.”

John Bucher is a toxicologist at the National Toxicology Program, or NTP, in Durham, N.C. That’s part of the National Institutes of Health. He did not work on the new study but noted the same limitations that Foerster’s group did. He did point out, however, that the study “was carefully done and took many factors into consideration.”

Bucher’s team has also studied effects of cell phone radiation — in rodents. Male rats that got high doses of the radiation had a higher cancer risk, the group found. That was not the case for female rats or mice.

“Because the animals were exposed to levels much higher than what people typically receive from cell phones, the [NTP] results cannot be directly applied to people,” Bucher says. Yet “they provide valuable information to help guide future studies of cell-phone safety as the technologies advance.”

A peer-review panel at NTP accepted the findings by Bucher’s group earlier this year, in March. Technical reports describing their findings are due to be published soon.

The U.S. Food and Drug Administration has tips for people who want to reduce their radiation exposure from phones, Bucher adds. Spend less time on your cell phone, it recommends. And use the phone’s speaker or a headset to keep the actual phone away from your ear.

Foerster agrees that it makes sense to take those simple steps. “In general,” she says, “the radiation decreases very, very fast as you increase the distance from the device.”