A new study found that working an average of more than 11 hours a day more than doubles the risk for depression.

Researchers observed over 2,000 civil servants in England, and found that the increased workload resulted in conflicts with family at home, problems winding down after the long day, and increased levels of cortisol, a stress-related hormone that can weaken immune systems and cause high blood pressure.

The study is published in the online journal PLoS One