Americans who are unemployed for long durations are twice more likely to be treated for depression than employed Americans, a new survey reveals.

The longer an American is out of a job, the more likely he is to suffer from a clinical case of depression. This is the finding of a new poll conducted by Gallup. The survey was conducted on 356,599 Americans, including 18,322 unemployed adults who were questioned about their well-being.

Researchers found that 10 percent of Americans who reported being unemployed for three to five weeks were either depressed or being treated for the mental disorder. This number rose to 17 percent among Americans that were unemployed for six months to a year. Among people who had been without a job for more than a year, 19 percent were battling depression, according to the Gallup-Healthways Well-Being Index.

Overall, unemployed Americans were twice more likely to be treated for depression than employed Americans (12.4 percent and 6.4 percent respectively). About 12.3 percent of people with short-term employment, which included employment for less than 27 hours per week were depressed. This number rose to 18 percent among long-term unemployed individuals.

Only 5.6 percent of full-time employed people said they were depressed or were receiving treatment for the disorder. Among people working part-time but not seeking a full time job, the number of depressed individuals was 8 percent. However, 10.3 percent of people working part-time because they couldn't find full time jobs said they were depressed.

These findings could better explain why people that have been unemployed for long durations are very pessimistic about findings a new job. The poll revealed that people who were unemployed for less than five weeks were 70 percent more optimistic about finding a new job in the next four weeks. For people who had been unemployed for more than a year, only 30 percent believed they'd be able to find a job in the near future.

While this study shows that unemployment may lead to depression, researchers don't rule out the possibility that the effect may work the other way round too. Depression may lead to unemployment.  The findings highlight the need for better psychological and social well-being analyses to help unemployed individuals find a job soon.

According to May statistics released by the Bureau of Labor Statistics, 9.8 million Americans were unemployed last month, including 3.4 million who were considered long-term unemployed.

The Gallup poll was conducted Jan. 1 to Dec. 31, 2013. All participants were aged 18 years and above. According to a UPI report, the margin of error is less than one percent point.