Like many bosses, Chris Mullen found the final hours of the weekend ideal for decluttering an unruly inbox, sharing stray thoughts with staff on projects and requesting status updates to prep for the week.

His colleagues felt otherwise. All those emails were pulling them into the workweek the evening before, he said, triggering the pre-Monday dread many working Americans call the “Sunday Scaries.”

“I asked my staff, ‘How come you keep answering my emails late at night, when you’re probably out with friends or relaxing at home?’” said the former college administrator. He recalled one employee’s response: “‘Because you’re the one sending it!’”

Workplace experts say such job creep has become a prime contributor to burnout—a phenomenon getting renewed attention since the World Health Organization included a more detailed description of it in the most recent edition of the International Classification of Diseases in May. Though the WHO stops short of calling burnout a medical condition, it describes it as a syndrome brought on by “chronic workplace stress that has not been successfully managed.”

The proliferation of smartphones and workplace communication apps has created unrealistic expectations of how easily—and often—workers should be able to switch from personal to professional tasks, researchers say.


In an April survey by Chicago-area mental-health center Yellowbrick, 62% of 2,059 working adults between the ages 23 and 38 said they felt pressure to be available around the clock through email, Slack and other work-communication channels. A recent study by researchers at Virginia Tech, Lehigh University and Colorado State University found that even the expectation of checking work emails on weekends and after-hours triggered anxiety and other harmful health effects among workers.

A 2018 analysis conducted by Microsoft Corp. researchers of the Sunday-evening email habits of tens of thousands of managers at U.S. companies suggests why: Every hour a boss spent online translated to 20 extra minutes of work for his or her direct reports outside of normal business hours, the study found. The study used anonymized data from Microsoft’s email and meeting services and information from human-resources departments across several large companies.

Even dwelling on work in the waning hours of the weekend can cause anxiety—a phenomenon so commonplace it has spawned the popular hashtag #SundayScaries. In a LinkedIn survey of more than 1,000 working adults last fall, 80% said they experienced a surge in stress related to their jobs on Sunday nights. Among millennials, the share was even higher, at 91%.

Some employers are addressing off-hours work creep. At telecom company Bandwidth Inc. in North Carolina, a vacation-blackout policy bars employees from attending to business during time off—forcing its 700 employees, including its chief executive, to pause projects or equip colleagues with the resources to cover for them, if necessary.


Health-care consulting firm Vynamic created an email tool to divert messages sent after 10 p.m. into an electronic queue, to be delivered the next day at 6 a.m. The system, called zzzMail, goes dark Friday evenings until Monday morning.

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CEO Jeff Dill said Vynamic’s 140 employees almost always stick to the ban. “When you’re in an environment where there’s time for structured disengagement, you’re able to gauge more clearly if something can wait until the next morning or after the holiday,” he said. “And 99% of the time it can absolutely wait, we’ve found,” he said.

Mindy McGrath, a health-care industry adviser at Vynamic, said she initially thought the email policy wouldn’t be feasible. Many colleagues had joined from consulting firms where the communication norm was “having a phone in-hand all the time, like it’s an appendage,” she said.

Ms. McGrath said it took her a few months to get used to ignoring her work devices after hours. One Saturday, she accidentally fired off an email she had intended to save as a draft.


“As soon as I sent it, I thought, ‘Holy smokes, what did I do? I have to get it back!,’” she said. Her boss texted soon after with a gentle reminder that she was free to unplug. Now, Ms. McGrath said she even deletes her work email from her cellphone on Fridays to ensure a screen-free weekend.

Still, some argue there is a case to be made for off-hour work emails. After a New York City councilman proposed legislation last year that would make it illegal for private employers to require workers check and respond to electronic communications after normal business hours, the bill was met with opposition from business groups and stalled.

Technology has made it easier for people to work whenever and wherever they want, blurring the divisions between personal and professional time, said Bryan Lozano of the trade association Tech:NYC at a January hearing on the proposal. It is no longer practical for many employers to set hard limits on when staff should be reachable, since business is being conducted around the clock, often by colleagues across the globe, he said.

Mr. Mullen, the former college administrator who is now a director of the human-resources consulting arm of workforce-management software company Kronos Inc., said the exchange with his former colleague prompted him to change his Sunday email habit. Though he still occasionally drafts them after putting his four children to bed, he waits to send them until the morning.


“There’s a power dynamic at play,” he said. “If I’m still sending you emails at night, as someone in a position of power over you, the team is going to feel the need to do the same.”

Write to Kelsey Gee at kelsey.gee@wsj.com