Being unemployed while trying to find a job is depressing. And the longer unemployment lasts, the more depressing it is.

Research has linked unemployment to depression but few studies have tried to distinguish between the effects of being out of the work force by choice and being unemployed and looking for a job.

As employment can be very important for a young person's identity and self-esteem, and depression often first manifests itself in young adults, researchers sought to find out if being out of work in young adulthood might influence depressive symptoms down the line.

Researchers analysed data from the National Longitudinal Survey of Youth, including young women and men in the United States, from 1979 to 1994. In one analysis, including 8,290 people who were 29 to 37 years old in 1994, they analysed the relationship between unemployment and depressive symptoms. In the second, they looked at whether the duration of time that these people were unemployed from 1979 to 1993 affected their level of depressive symptoms in 1994. This analysis included 6,891 people.

Five percent of those surveyed in 1979 were out of work and looking for a job, while 17 percent were neither working nor looking for work. People were unemployed and looking for work for about 18 months, on average, while the average amount of time being jobless was 3.2 years.

It was found that the length of time a person had been unemployed influenced their level of depressive symptoms when they were 29 to 37 years old, with the same effects for men and women. This was independent of whether a person was poor or whether they had a negative net worth - both of which can be depressing. The researchers also found that the effect of unemployment duration was independent of whether a person reported symptoms of depression two years before. But being out of the work force and not looking for work had no effect, overall, on people's level of depressive symptoms.

When young people are unemployed and they can't find work over long periods of time it can affect their mental health. There is a need for interventions to help young people navigate between school and work. Such efforts could save money given the long-term toll depression and stress can take on physical as well as mental health.