During the second week, we flipped the instructions, so the email-maximizers became the email-minimizers, and vice versa. This design allowed us to compare how stressed the same individuals felt when they checked their email more versus less often, while keeping everything else constant.

At the end of each weekday, the participants reported how the day had gone on a wide range of measures. To assess stress, we asked them, for example, how often they felt unable to control the important things in their life and how often they had trouble coping with all the things they had to do that day.

Although the only thing we changed about the participants’ lives was how often they checked their email, we observed a significant reduction in stress when they checked email less frequently. How much less stressed did people feel during their email-minimizing week compared with their email-maximizing week? The reduction in stress was about as large as the benefit people get from learning relaxation techniques (e.g., taking deep breaths, visualizing peaceful imagery). In other words, cutting back on email might reduce stress as much as picturing yourself swimming in the warm waters of a tropical island several times a day.

Checking email less often may reduce stress in part by cutting down on the need to switch between tasks. An unfortunate limitation of the human mind is that it cannot perform two demanding tasks simultaneously, so flipping back and forth between two different tasks saps cognitive resources. As a result, people can become less efficient in each of the tasks they need to accomplish. In addition to providing an unending source of new tasks for our to-do lists, email could also be making us less efficient at accomplishing those tasks.

Indeed, although the participants in our study sent and received roughly the same number of emails during both weeks, they reported doing so in approximately 20 percent less time during the week when they checked their email less frequently. Constantly monitoring our inboxes promotes stress without promoting efficiency. When it comes to checking email, less might be more.