A moldy home, especially one plagued with toxic black mold, has long been linked to health problems.

And a new public health study now links damp, moldy homes to depression.

The findings, published in the American Journal of Public Health, came as a complete surprise to lead author, Brown University epidemiologist Edmond Shenassa.

In fact, after a few U.K. studies published in the last decade had suggested a link, Shenassa and his team set out to debunk the notion that any link existed.

“We thought that once we statistically accounted for factors that could clearly contribute to depression – things like employment status and crowding – we would see any link vanish,” said Shenassa, an associate professor in the Department of Community Health at Brown, in a news release. “But the opposite was true. We found a solid association between depression and living in a damp, moldy home.”

Shenassa said the study, an analysis of data from nearly 6,000 European adults, does not prove that moldy homes cause depression.

The study wasn’t designed to draw that direct conclusion. But Shenassa’s team did find a connection. One likely driven by two factors: a perceived lack of control over the housing environment by the persons living there and mold-related health problems such as wheezing, fatigue and a cold or throat illness.

“Physical health, and perceptions of control, are linked with an elevated risk for depression,” Shenassa said, “and that makes sense. If you are sick from mold, and feel you can’t get rid of it, it may affect your mental health.”

The study was a statistical analysis of data from the Large Analysis and Review of European Housing and Health Status (LARES), a survey on housing, health and place of residence conducted in 2002 and 2003 by the World Health Organization (WHO).

To conduct the survey, WHO interviewers visited thousands of homes in eight European cities and asked residents a series of questions, including if they had depressive symptoms such as decreased appetite, low self-esteem, and sleep disturbances. WHO interviewers also made visual checks of each household, looking for spots on walls and ceilings that indicate mold.

Shenassa’s team analyzed LARES data from 5,882 adults in 2,982 households.

“What the study makes clear is the importance of housing as indicator of health, including mental health,” Shenassa said. “Healthy homes can promote healthy lives.”

Shenassa and his team are conducting follow-up research to see if mold directly causes depression.