More than a third of US homeowners in foreclosure show signs of serious depression, according to a medical study published Tuesday, highlighting the crisis' hidden impact on public health.

"The foreclosure crisis is also a health crisis," said lead author Craig Pollack, a professor at the University of Pennsylvania. "We need to do more to ensure that if people lose their homes, they don't also lose their health."

Nearly half of a group of 250 people in Philadelphia whose homes were in foreclosure reported depressive symptoms, and 37 percent "met screening criteria for major depression," according a study by the University of Pennsylvania School of Medicine.

The research was published online this week in the American Journal of Public Health.

The study said the level of depressive symptoms is "exceptionally high" compared to previous research that showed that around 12.8 percent of people living in poverty suffer from major depressive disorder.

The situation could be even worse in other major US cities, where foreclosure and unemployment figures are higher than in Philadelphia, where foreclosures nearly doubled between 2007 and 2008.

The study found that homeowners undergoing foreclosure were less likely to have health insurance than the average American, 22 percent of those being foreclosed upon were uninsured, compared with eight percent of the population as a whole.

In the case of nine percent of those being foreclosed upon, medical expenses were the reason they were losing their home, and a quarter of all those in foreclosure said they had unpaid medical bills.