Elisabeth Kleppa and colleagues of the University of Bergen, Norway, analyzed data on work hours from a larger study of Norwegian men and women.
Symptoms of anxiety and depression were assessed using a standard screening questionnaire. Anxiety and depression scores were compared for 1,350 workers who worked overtime, 41 to 100 hours per week; and approximately 9,000 workers who worked normal hours, 40 hours or less.
Working overtime was associated with higher anxiety and depression scores among both men and women. The rate of questionnaire scores indicating “possible” depression increased from about nine percent for men with normal work hours to 12.5 percent for those who worked overtime.
For women, the rate of possible depression increased from seven to eleven percent. In both sexes, rates of possible anxiety and depression were higher among workers with lower incomes and for less-skilled workers.
The relationship between overtime and anxiety/depression was strongest among men who worked the most overtime — 49 to 100 hours per week. Men working such very long hours also had higher rates of heavy manual labor and shift work and lower levels of work skills and education.
Previous studies have raised possible health and safety concerns of working long hours. However, most studies of this issue have focused on the health effects of shift work, rather than overtime. Under European Union work rules, employees have the right to refuse to work more than 48 hours per week.
The new results support this directive by showing increased rates of anxiety and depression among overtime workers. Men working more than 48 hours per week are at highest risk, although the authors note that working even moderate overtime hours seems to increase the risk of “mental distress.”
The study permits no conclusions about how working long hours leads to increased anxiety and depression. It could be that working overtime leads to increased “wear and tear,” or that individuals with characteristics predisposing to anxiety and depression (such as low education and job skills) are more likely to take jobs requiring long work hours.
The study is published in the June Journal of Occupational and Environmental Medicine.