People who talk on their cell phones in the evening may have trouble getting to sleep, according to a news wire report that appeared on PhysOrg.com.

Bengt Arnetz, a researcher from Sweden's Uppsala University, said that radiation from mobile phones causes insomnia, headaches and problems concentrating.

Scientists from Sweden and Wayne State University studied 35 men and 36 women between the ages of 18 and 45 for 18 months. They were intermittently exposed to wireless signals that simulated the radiation received when talking on a cell phone.

Others were put in similar situations but not exposed to radiation.

"The ones who were exposed reported headaches, it took longer for them to fall asleep and they did not sleep as well through the night," Arnetz said.