If you're tired and grumpy, it may well be the fault of cell phones. No, not that everyone everywhere — from the grocery store to the golf course — is talking on one, as maddening as that is.

According to a new study released jointly by Wayne State University in the US and the Karolinska Institute in Sweeden, the radiation given off by cell phones may be to blame for lack of sleep. Researchers found that subjects exposed to radiation equivalent to what is given off by an average cell phone shortly before bed were less able to get restful sleep. Apparently, cell phone radiation increases the time required to enter deep sleep, and shortens the amount of time the subject spends in deep sleep. As these deep sleep cycles are critical to waking rested and refreshed, it looks like leaving the cell glued to your ear late into the night may be responsible for getting up on the wrong side of the bed the next morning.

Read more.