WASHINGTON, D.C. – A U.S. insurance study has revealed that drivers using cell phones are four times as likely to be involved in an accident that causes injuries serious enough to send them to hospital.

The U.S. Insurance Institute for Highway Safety released the findings, and as a result of the study also said even hands-free devices may not be enough to improve safety. The organization also said it was the first study of its kind.

“You’d think using a hands-free phone would be less distracting, so it wouldn’t increase crash risk as much as using a hand-held phone. But we found that either phone type increased the risk,” Anne McCartt, one of the study’s authors told reporters.