Short-term household debt, such as credit cards and overdue bills, increases depressive symptoms, according to a recent study.

Researchers at the University of Wisconsin-Madison found that this association was particularly strong among unmarried people, people reaching retirement age and those who are less well educated. The study shows the impact of different types of debt on depression and their effects on different sectors of the United States population. Little evidence was found for an association with mid- or long-term debt.

"New debt contracts could be offered to vulnerable borrowers and the population sectors we identified could be targeted with help in building their financial capacity," Lawrence Berger, lead author of the study, said in a statement. "The findings could also be used to help mental health practitioners better understand the impact of clients' borrowing habits on depression."

For the study, researchers collected and analyzed data from nearly 8,500 working-age adults. The data were taken from two waves of the National Survey of Families and Households, conducted six years apart and ending in 1994. Overall findings included the fact that 79 percent of respondents had some debt, totaling an average of $42,000. Long-term debt accounted for by far the largest portion.

They found that those who had debt were younger, more likely to be male, less likely to be black or Hispanic, had more highly educated parents, were more highly educated themselves, were more likely to be married and working, had greater income and assets, and were in better health.

It was when the researchers began to adjust for measures of socio-economic status, and to refine their analysis to subgroups defined by age, education and marital status, that a negative association began to emerge. They also controlled for reverse causality to check that debt was causing depression and not vice versa.

Spurred by increased homeownership and an increase in unsecured revolving credit card debt, household debt has increased dramatically in the last 40 years. While it has declined since 2008 as credit has become more difficult to obtain, it remains at historically high levels.

The findings are detailed in the Journal of Family and Economic Issues.