Research suggests a connection between early exposure to cellphones and behavior problems in children.

RODALE NEWS, EMMAUS, PA—Very few of us know somebody who doesn't have a cellphone. Yet, very few of us have any idea what impact our handy, must-have cellphones have on our health. So far, some research suggests that their overall health impact could be as minor as causing ringing in the ears, but other studies suggest that cellphones cause other biological changes that aren't yet entirely clear. Earlier this year, the U.S. Senate even pressed researchers to provide them with more concrete evidence that cellphones are either safe or are potential cancer causers.

"It's impossible to know what the real long-term risks are," says Diana Zuckerman, PhD, president of the Cancer Prevention and Treatment Fund, "and we're probably not going to know for 20 years." But that doesn't mean we shouldn't be concerned about how cellphones affect our health right now—or the health of our kids. Adding to the concerns: A recent study published in the Journal of Epidemiology and Community Health has found that cellphones could be associated with bad behavior among children.

THE DETAILS: The authors looked at data collected from an ongoing study in Denmark on pregnant women and their children. In an earlier study, the research had found that children born in 1996 and 1997, the early days of cellphone use, were more likely to have behavioral problems by age 7 if their mothers were regular users of cellphones both during and after pregnancy. Because those mothers may have been early adopters of technology (a personality trait that is usually associated with behavioral issues that can be passed on to children, according to the study authors), they repeated their analysis with children born between 1998 and 2002. Mothers of those children answered questionnaires about their cellphone use during and after pregnancy, and when the children turned 7, their mothers answered questions about their psychological history and any potential behavioral problems.

Just over 17 percent of the mothers in the new study (children born between 1998 and 2002) reported using cellphones during pregnancy, and in both the first study (children born in 1996 and 1997) and the new study, approximately one third of children were using cellphones by the age of 7. Though the difference was small, the children with the highest risk of behavioral problems were more likely to have mothers who used cellphones both before and during pregnancy than children whose mothers didn't use them at all. To determine whether the increase in behavior risk may have had something to do with a mother's inattention (moms who are always on the cellphone may not pay as much attention to their children, thus leading to cranky kids), they looked at breastfeeding rates, which helped determine how much time they spent with a child in his or her first months of life. But that didn't seem to have any affect on child behavior.

WHAT IT MEANS: The "why" behind these findings isn't immediately obvious, says the study's lead author Leeka Kheifets, PhD, professor of epidemiology at the University of California–Los Angeles. "People have postulated different things, like it could interfere with hormones, but there's no reason to think it's true or not true."