Women who work more than 55 hours per week are more likely to suffer depression than those who work at a more standard 35-40 hours, a British study found.
In contrast, men who have placed at the same time are not more likely to show signs of this condition, the researchers said. They suggest that this may be due to the fact that women face a "double load" of very long hours spent doing their homework, which they do far more than male partners.
Both men and women who work most or all weekends are more likely to become depressed than those who work only during the week, research has also found.
The results are based on data from more than 20,000 British adults participating in "Understanding the Society": the household survey in the UK, which since 2009 has been tracking family life and society.
Women who work at least 55 hours a week had a 7.3% greater chance of depressive symptoms than those who worked between 35 and 40 hours.
Women were also more likely than men to show signs of exhausting moods related to work on Saturdays and Sundays, though both were affected (4.6% and 3.4% more likely).
"Women are generally more likely to be depressed than men, and that's no different in the study," said lead author of the study, Gil Weston, a PhD student at University College London.
"Regardless of the patterns of work, we found that workers with the most depressive symptoms are older, lower-income, smoker, physically hard-working, and unhappy with work."
Two-thirds of men work on Saturdays and Sundays compared to half of women, according to the study published in the journal Epidemiology and Public Health.
The NHS Digital study found that 19% of women in England suffered from a common mental disorder – mainly anxiety or depression – and about 12% of men. Likewise, 10% of women and 6% of men experience severe symptoms in each of these conditions.
Weston stressed that the findings of the authors do not prove that long hours lead directly to depression.
"This is a monitoring study so that although we can not identify the exact causes, we know that many women face an extra burden to make a greater share of local labor than men, leading to extensive working time, adding time pressure and huge responsibilities, "she said.
Andy Bell, Deputy Executive Director of the Center for Mental Health, says: "Long hours can be symptomatic of insecurity and unrealistic expectations at work, which are known as risk factors for poor mental health. So the context in which a person works long hours can be as important as the time spent working. "