According to a study from Glasgow and Paisley universities, e-mail is the cause for many productivity lapses and work stress.  Three researchers monitored 177 employees to see how they react to the never-ending stream of email most of us are subjected to on a daily basis.  The results?  Over a third of the participants reported stress over the obligation to quickly respond to incoming mail.  Another 28 percent said it was the volume of mail that caused them stress.  Oddly, approximately 38 percent said that email keeps them feeling relaxed, though that's because they typically take several days or weeks to respond to any message.

In the study, 50% of participants claimed to check their email once an hour, and 35% said they checked every 15minutes.  The reality though was that these people were checking their inbox upwards of 30-40 times per hour (that's once every 1.5-2min).  There's no question that this frequency is cutting into time spent on other, often more important tasks.

Ars Technica has a more complete write-up on the study, which you can find at the link below.

So, how often do you check your email?  Does it dominate your life like the folks in the study?