Your boss may love you for putting in 11-hour days, but it could be taking a toll on your emotional health. A new study shows regularly logging long hours can more than double your risk of depression.

In research published in the online journal PLoS ONE, scientists reviewed a 1991 study of more than 2,000 British civil servants with an average age of 47 who had no mental health problems — but six years later, 66 cases of major depression were found in those workers.

The data showed that compared to public employees who logged less than eight daily office hours, those who worked more than 11-hour days had a more than twofold increased risk of depression. This effect was most prominent in younger women in lower job grades who used alcohol moderately and also had a chronic disease.

“Long working hours are likely to be related to less time to relax and less sleep,” said study researcher Marianna Virtanen, PhD, a team leader of the Work and Mental Health team at the Finnish Institute of Occupational Health in Helsinki. “It is also possible that excessive working hours result in problems with close relationships, which in turn, may trigger depression.”

While much of this research was done two decades ago, the findings may be even more relevant now. “Work is no longer so much tied to time and place,” Virtanen said. “This may make some people feel highly attached to their work tasks outside of their usual working hours.”

“Although occasionally working overtime may have benefits for the individual and society,” she said in a press release, “it is important to recognize that working excessive hours is also associated with an increased risk of major depression.”