Researchers at the University of Pennsylvania and the University of California, Berkeley, found that people who work in the service sector and have unpredictable, unstable schedules experience a range of negative physical and mental consequences.

“People have long suspected that this was the case,” said Kristen Harknett, an adjunct associate professor in Penn’s sociology department in the School of Arts & Sciences. But “we haven’t had systematic evidence.”

Dr. Harknett and Daniel Schneider, assistant professor at Berkeley, focused on two dimensions: the amount of notice employees have for their work schedules and amount of instability in those schedules.

They used Facebook ads targeted at 18- to 50-year-olds who were employed by eight of the largest retailers across the country, where these scheduling practices are common. The ads offered a lottery incentive to employees who took a 20-minute online survey. About 6,000 responses were received.

The survey results showed that those who were given more lead time about work days and hours experienced less stress, better overall health and less trouble sleeping. In addition, more lead time led to more time with children for working parents.

“There’s a lot of anecdotal evidence about how harmful these practices [of giving employees unstable and unpredictable schedules] are and how difficult the lives of working parents are when they have a complete inability to plan,” Dr. Harknett said. “If you don’t know your work schedule in advance, you can’t have a second job, you can’t go to school, you can’t have a regular child-care arrangement. Everything has to be arranged at the last minute.”