Elisabeth Kleppa and colleagues at the University of Bergen in Norway analyzed data on work hours from a larger study of Norwegian men and women. The researchers used a standard screening questionnaire to assess symptoms of 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 40 hours or less.
While previous studies have raised possible health and safety concerns of working long hours, most have focused on the health effects of shift work rather than overtime. This new research shows that working overtime is 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 11 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 long hours also had higher rates of heavy manual labor and shift work and lower levels of work skills and education. The authors added, however, that even those who work moderate overtime hours face an increased risk of “mental distress.”
The study permits no conclusions about how working long hours leads to increased anxiety and depression. The authors note that working overtime leads to increased "wear and tear," or that individuals with characteristics predisposing to anxiety and depression (such as limited education and job skills) are more likely to take jobs requiring long work hours.