June 19 (HealthDay News) -- Working overtime puts you at a higher risk for developing anxiety and depression, a new study suggests.

Men who worked 40 hours a week or less had a 9 percent "possible" depression score on standard screening questionnaires, while 12.5 percent of their counterparts who worked overtime showed signs of depression and anxiety. For women, the possible depression rate increased from 7 percent to 11 percent.

The results, published in the June issue of the Journal of Occupational and Environmental Medicine, also show anxiety and depression rates were higher among less-skilled workers and those with lower incomes. The study looked at 1,350 overtime workers and 9,000 with normal work hours in Norway.

Men who worked the most overtime -- nine to 60 hours a week -- showed the greatest link to anxiety and depression. These men tended to have lower work skills and education levels than others and have jobs involving heavy manual labor and shift work. While these men were at highest risk, even moderate overtime work appeared to bump up the risk of "mental distress," the authors noted.

What causes working long hours to increase anxiety and depression was not explored in the study.

SOURCE: American College of Occupational and Environmental Medicine, news release, June 15, 2008